Bio

Clinical Focus


  • Ophthalmology

Academic Appointments


Honors & Awards


  • Biodesign Certificate of Appreciation, Stanford Biodesign (2011)
  • Best Paper Award, American Academy of Ophthalmology (2008)
  • American Academy of Ophthalmology Achievement Award, American Academy of Ophthalmology (2008)
  • America’s Top Ophthalmologist, Consumers' Research Council of America (.)
  • Best Poster Award, European Society of Cataract and Refractive Surgery Conference (2005)
  • Alpha Omega Alpha, Alpha Omega Alpha (1993)
  • Phi Beta Kappa Honor Society, Phi Beta Kappa (1990)

Professional Education


  • Board Certification: Ophthalmology, American Board of Ophthalmology (2000)
  • Residency:Stanford University School of Medicine (1998) CA
  • Fellowship:Univ Of Texas Southwestern (1999) TX
  • Residency, Stanford University, Ophthalmology (1998)
  • Internship:Kaiser Foundation Hospital-Oakland (1995) CA
  • Medical Education:University of Minnesota (1994) MN
  • BA, University of Minnesota, Physiology (1990)

Research & Scholarship

Clinical Trials


  • Cyclosporine Eye Drops in Preventing Graft-Versus-Host Disease of the Eye in Patients Who Have Undergone Donor Stem Cell Transplant for Hematologic Cancer or Bone Marrow Failure Disorder Not Recruiting

    RATIONALE: Cyclosporine eye drops may prevent graft-versus-host disease of the eye in patients who have undergone donor stem cell transplant for hematologic cancer or bone marrow failure disorder. PURPOSE: This randomized phase I trial is studying how well cyclosporine eye drops work in preventing graft-versus-host disease of the eye in patients who have undergone donor stem cell transplant for hematologic cancer or bone marrow failure disorder.

    Stanford is currently not accepting patients for this trial. For more information, please contact Joanne Otani, (650) 721 - 2372.

    View full details

Teaching

2013-14 Courses


Publications

Journal Articles


  • Application of 10% povidone iodine reduces conjunctival bacterial contamination rate in patients undergoing cataract surgery EUROPEAN JOURNAL OF OPHTHALMOLOGY Nentwich, M. M., Rajab, M., Ta, C. N., He, L., Grueterich, M., Haritoglou, C., Gandorfer, A., Kampik, A., de Kaspar, H. M. 2012; 22 (4): 541-546

    Abstract

    To determine the efficacy of 10% povidone iodine (PVI) drops given before cataract extraction in addition to routine irrigation of the conjunctival sac with 1% PVI.This prospective, randomized, single-center study at the Department of Ophthalmology, Ludwig-Maximilians-University, Munich, includes 263 eyes of 242 patients undergoing cataract surgery. Patients were randomized to receive 3 drops of 10% PVI into the conjunctival sac (study group) or no PVI drops (control group). All patients underwent periorbital disinfection with 10% PVI followed by irrigation of the conjunctiva with 10 mL of 1% PVI. Specimens were obtained prior to the application of PVI, after antibiotic administration (T1), after irrigation with PVI but before surgery (T2), and at the conclusion of surgery (T3).After PVI disinfection, the number of positive cultures was significantly reduced in all groups (p<0.0001) from 69%-93% at T1 to 1%-16% at T3. In outpatients, the study group showed significantly fewer positive cultures at the conclusion of surgery compared to the control group (4% vs 16%; p=0.03). Also in inpatients significant fewer positive cultures were found in the study group compared to the control group at T2 (12% vs 28%; p=0.03) and at T3 (1% vs 10%; p=0.03).Three additional drops of 10% PVI prior to surgery provided additional benefit by reducing the conjunctival bacterial contamination rate even in the setting of preoperative irrigation of the conjunctiva with 1% PVI.

    View details for DOI 10.5301/ejo.5000093

    View details for Web of Science ID 000310266900002

  • Diffusion of Protein through the Human Cornea OPHTHALMIC RESEARCH Charalel, R. A., Engberg, K., Noolandi, J., Cochran, J. R., Frank, C., Ta, C. N. 2012; 48 (1): 50-55

    Abstract

    To determine the rate of diffusion of myoglobin and bovine serum albumin (BSA) through the human cornea. These small proteins have hydrodynamic diameters of approximately 4.4 and 7.2 nm, and molecular weights of 16.7 and 66 kDa, for myoglobin and BSA, respectively.Diffusion coefficients were measured using a diffusion chamber where the protein of interest and balanced salt solution were in different chambers separated by an ex vivo human cornea. Protein concentrations in the balanced salt solution chamber were measured over time. Diffusion coefficients were calculated using equations derived from Fick's law and conservation of mass in a closed system.Our experiments demonstrate that the diffusion coefficient of myoglobin is 5.5 ± 0.9 × 10(-8) cm(2)/s (n = 8; SD = 1.3 × 10(-8) cm(2)/s; 95% CI: 4.6 × 10(-8) to 6.4 × 10(-8) cm(2)/s) and the diffusion coefficient of BSA is 3.1 ± 1.0 × 10(-8) cm(2)/s (n = 8; SD = 1.4 × 10(-8) cm(2)/s; 95% CI: 2.1 × 10(-8) to 4.1 × 10(-8) cm(2)/s).Our study suggests that molecules as large as 7.2 nm may be able to passively diffuse through the human cornea. With applications in pharmacotherapy and the development of an artificial cornea, further experiments are warranted to fully understand the limits of human corneal diffusion and its clinical relevance.

    View details for DOI 10.1159/000329794

    View details for Web of Science ID 000305551100009

    View details for PubMedID 22398578

  • Should we be concerned about antibiotic resistance when using intravitreal injections Expert Reviews in Ophthalmology Ko MS, Ta CN 2012; 7 (5): 393-395
  • Prevention of postcataract endophthalmitis: evidence-based medicine CURRENT OPINION IN OPHTHALMOLOGY Yu, C. Q., Ta, C. N. 2012; 23 (1): 19-25

    Abstract

    To provide a summary of current peer-reviewed publications on the methods of prophylaxis against postcataract endophthalmitis.Preoperative application of povidone-iodine remains the standard protocol for the prevention of postoperative endophthalmitis. More recent evidence suggests that intracameral cefuroxime administered at the conclusion of surgery significantly reduces the risk of endophthalmitis. However, its clinical use has been limited because of a lack of commercially available antibiotic indicated for intraocular injection. Although topical antibiotic application continues to be a controversial topic with respect to the types of antibiotic prescribed and dosage, most ophthalmologists do prescribe an antibiotic for the perioperative period. Resistance against antibiotics, including the very popular classes of fluoroquinolones, is rising. Most notably, methicillin resistance continues to increase over time.Prevention of postcataract endophthalmitis remains a difficult topic to study given the low incidence. In addition to appropriate wound construction, a combination of povidone-iodine and antibiotics provide a reasonable approach in reducing the risk of this rare but serious infection.

    View details for DOI 10.1097/ICU.0b013e32834cd5a9

    View details for Web of Science ID 000298150700005

    View details for PubMedID 22081026

  • Toward the development of an artificial cornea: Improved stability of interpenetrating polymer networks JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS Hartmann, L., Watanabe, K., Zheng, L. L., Kim, C., Beck, S. E., Huie, P., Noolandi, J., Cochran, J. R., Ta, C. N., Frank, C. W. 2011; 98B (1): 8-17

    Abstract

    A novel interpenetrating network (IPN) based on poly(ethylene glycol) (PEG) and poly(acrylic acid) was developed and its use as an artificial cornea was evaluated in vivo. The in vivo results of a first set of corneal inlays based on PEG-diacrylate precursor showed inflammation of the treated eyes and haze in the corneas. The insufficient biocompatibility could be correlated to poor long-term stability of the implant caused by hydrolytic degradation over time. Adapting the hydrogel chemistry by replacing hydrolysable acrylate functionalities with stable acrylamide functionalities was shown to increase the long-term stability of the resulting IPNs under hydrolytic conditions. This new set of hydrogel implants now shows increased biocompatibility in vivo. Rabbits with corneal inlay implants are healthy and have clear cornea and non-inflamed eyes for up to 6 months after implantation.

    View details for DOI 10.1002/jbm.b.31806

    View details for Web of Science ID 000291598900002

  • Long-term Clinical Course of Dry Eye in Patients With Chronic Graft-Versus-Host Disease Referred for Eye Examination CORNEA Sales, C. S., Johnston, L. J., Ta, C. N. 2011; 30 (2): 143-149

    Abstract

    To assess the long-term clinical course of dry eye in patients with chronic graft-versus-host disease (cGVHD).A prospective case series of 49 patients with cGVHD was conducted. Complete history and ophthalmic examination were performed at baseline and at 36 months (range, 26-53). All patients received treatment for dry eye.Of the 49 participants, 18 (37%) had expired at the time of the 3-year eye examination, 11 were lost to follow-up, 11 declined or were unable to attend the final examination, and 9 (18%) completed the study. There was a statistically insignificant improvement in symptoms of dry eye assessed by the ocular surface disease index [start vs. endpoint: 36 ± 22 (range, 4-72) vs. 30 ± 27 (range, 4-86); P = 0.51]. Visual acuity remained stable at approximately 20/20. Lissamine green staining improved and Schirmer test (with anesthetic) worsened, but neither trend was statistically or clinically significant.Stable visual acuity, tear production, and lissamine green staining and a statistically insignificant improvement in dry eye symptoms were observed in the 9 participants who completed this 3-year prospective case series of 49 patients with cGVHD. Insofar as these patients represent a minority (18%) of the original cohort, their clinical course may not be generalizable to all patients with cGVHD but may still suggest that this patient population's prognosis could be characterized by stability and excellent vision. Sufficiently powered prospective studies are required to validate these postulates.

    View details for DOI 10.1097/ICO.0b013e3181e9b3bf

    View details for Web of Science ID 000285914700006

    View details for PubMedID 20885310

  • Corneal decompensation in Axenfeld-Rieger syndrome and associated histopathological findings Minerva Oftalmologica Ta CN, Sun Y 2011; 53 (1): 29-30
  • Structure and Mechanism of Strength Enhancement in Interpenetrating Polymer Network Hydrogels Macromolecules Waters D, Engberg K, Parke-Houben R, Ta CN, Jackson A, Toney M, Frank C 2011; 44 (14): 5776-5787
  • Antibiotic Susceptibility Patterns of Ocular Bacterial Flora in Patients Undergoing Intravitreal Injections OPHTHALMOLOGY Moss, J. M., Sanislo, S. R., Ta, C. N. 2010; 117 (11): 2141-2145

    Abstract

    To determine the antibiotic susceptibility patterns of conjunctival flora in patients undergoing intravitreal (IVT) injection.Prospective, observational study.Patients (n = 85) scheduled to undergo 136 IVT injections at California Vitreoretinal Center at Stanford University.Conjunctival cultures were obtained on the day of the IVT injection from the injection site bulbar conjunctiva before the application of povidone-iodine or antibiotics.Bacterial isolates were identified and tested for antibiotic susceptibility using either the Kirby-Bauer disc-diffusion technique or MicroScan-WalkAway system.Our analysis included 136 samples collected from 90 eyes of 85 patients. Of those with positive cultures (n = 65), the most common bacterial isolates were coagulase-negative staphylococci (CNS), comprising 59 (83%) of the 71 bacterial strains. Among the CNS, all were susceptible to vancomycin and >80% were susceptible to gentamicin, chloramphenicol, tetracycline, and imipenem. Between 60% and 80% of the CNS were susceptible to the cephalosporins and newer generation fluoroquinolones. Fewer than 60% were susceptible to the penicillin analogs, erythromycin, and the earlier generation fluoroquinolones. Nearly half of the CNS (47%) were resistant to oxacillin/methicillin.Bacteria isolated from the injection site of patients undergoing IVT injections were mostly CNS. Most are sensitive to vancomycin, gentamicin, and chloramphenicol.Proprietary or commercial disclosure may be found after the references.

    View details for DOI 10.1016/j.ophtha.2010.02.030

    View details for Web of Science ID 000283264200016

    View details for PubMedID 20561687

  • Morphology of Photopolymerized End-Linked Poly(ethylene glycol) Hydrogels by Small-Angle X-ray Scattering MACROMOLECULES Waters, D. J., Engberg, K., Parke-Houben, R., Hartmann, L., Ta, C. N., Toney, M. F., Frank, C. W. 2010; 43 (16): 6861-6870

    Abstract

    Due to the biocompatibility of poly(ethylene glycol) (PEG), PEG-based hydrogels have attracted considerable interest for use as biomaterials in tissue engineering applications. In this work, we show that PEG-based hydrogels prepared by photopolymerization of PEG macromonomers functionalized with either acrylate or acrylamide end-groups generate networks with crosslink junctions of high functionality. Although the crosslink functionality is not well controlled, the resultant networks are sufficiently well ordered to generate a distinct correlation peak in the small angle x-ray scattering (SAXS) related to the distance between crosslink junctions within the PEG network. The crosslink spacing is a useful probe of the PEG chain conformation within the hydrogel and ranges from approximately 6 to 16 nm, dependent upon both the volume fraction of polymer and the molecular weight of the PEG macromonomers. The presence of a peak in the scattering of photopolymerized PEG networks is also correlated with an enhanced compressive modulus in comparison to PEG networks reported in the literature with much lower crosslink functionality that exhibit no scattering peak. This comparison demonstrates that the method used to link together PEG macromonomers has a critical impact on both the nanoscale structure and the macroscopic properties of the resultant hydrogel network.

    View details for DOI 10.1021/ma101070s

    View details for Web of Science ID 000280855000042

    View details for PubMedID 21403767

  • One-day application of topical moxifloxacin 0.5% to select for fluoroquinolone-resistant coagulase-negative Staphylococcus JOURNAL OF CATARACT AND REFRACTIVE SURGERY He, L., Ta, C. N., de Kaspar, H. M. 2009; 35 (10): 1715-1718

    Abstract

    To compare selection for fluoroquinolone-resistant bacteria between 1-day and 3-day application of topical moxifloxacin 0.5%.Department of Ophthalmology, Stanford University, Stanford, California, USA.After investigative review board approval, patients scheduled for ocular surgery were randomized to receive topical moxifloxacin 0.5% drops 4 times a day for 1 day or 3 days preoperatively. Conjunctival cultures were obtained at baseline and after antibiotic application. Bacteria were identified and tested for resistance to a battery of antibiotic agents using the Kirby-Bauer disk-diffusion method. The differences in resistance distributions for the most commonly isolated bacteria between baseline (T0) and after antibiotic administration (T1) were compared between the 2 treatment groups.Coagulase-negative Staphylococcus (CNS) were the most common bacteria isolated at T0 and T1. At T0, the proportion of CNS isolated in the 1-day group (n = 63) that was resistant to fluoroquinolones ranged from 4% to 22% depending on the antibiotic agent tested. After 1-day treatment with moxifloxacin, the percentage of resistant bacteria increased significantly (range 13% to 67%) for all fluoroquinolones except gatifloxacin (P<.05). Resistance to gentamicin and tobramycin also increased significantly. However, patients treated for 3 days (n = 57) showed no differences in bacterial resistance rates to any antibiotic agent tested.Prophylactic topical moxifloxacin 0.5% treatment starting 1 day before ocular surgery resulted in a significant increase in fluoroquinolone-resistant bacteria, while a 3-day antibiotic regimen did not select for resistant organisms.

    View details for DOI 10.1016/j.jcrs.2009.04.042

    View details for Web of Science ID 000270917300012

    View details for PubMedID 19781465

  • Prospective study of risk factors for conjunctival bacterial contamination in patients undergoing intraocular surgery EUROPEAN JOURNAL OF OPHTHALMOLOGY de Kaspar, H. M., Ta, C. N., Froehlich, S. J., Schaller, U. C., Engelbert, M., Klauss, V., Kampik, A. 2009; 19 (5): 717-722

    Abstract

    To determine whether a patient's age, gender, local or systemic risk factors affect the rate of preoperative bacterial contamination.Consecutive 1,474 patients undergoing intraocular surgery were enrolled in this prospective masked study. Past medical history was noted and examinations were performed. The patients were divided into four groups: a control group (without local or systemic risk factors), those with local risk factors (chronic use of topical medications, contact lens wear, blepharitis, chronic eyelid or conjunctival inflammation), those with systemic risk factors (immunosuppression, diabetes, autoimmune conditions, and asthma), and those with both. Conjunctival cultures were obtained before surgery.Among the 1,474 patients, 914 bacteria were isolated from 214 (14.9%) patients. Advanced age was associated with a higher rate of positive conjunctival cultures (p<0.005). No statistical difference was found with regard to gender (p=0.7173). Among the 282 patients in the control group, 14 (5%) had a positive conjunctival culture. Compared to the control group, positive conjunctival cultures were found in 118 out of 503 patients (23.5%) with local risk factors (p<0.0001), 65 out of 545 patients (11.9%) with systemic risk factors (p=0.0019), and 22 out of 144 (15.3%) with both (p=0.0006). Two patients developed postoperative endophthalmitis (0.14%), one with both local risk and systemic factors and the other with a systemic risk factor.Patients with local or systemic risk factors or advanced age were found to have a higher rate of bacterial conjunctival contamination before intraocular surgery.

    View details for Web of Science ID 000271845100004

    View details for PubMedID 19787587

  • A Prospective Randomized Evaluation of Topical Gatifloxacin on Conjunctival Flora in Patients Undergoing Intravitreal Injections OPHTHALMOLOGY Moss, J. M., Sanislo, S. R., Ta, C. N. 2009; 116 (8): 1498-1501

    Abstract

    We sought to assess the efficacy of 3-day topical gatifloxacin use in combination with povidone-iodine (PVI) versus PVI alone in eliminating conjunctival bacterial flora in patients scheduled to undergo intravitreal (IVT) injection.Prospective, randomized single-blind clinical trial.We included 129 patients scheduled to undergo 273 IVT injections at California Vitreoretinal Center at Stanford University.Study patients were randomized to self-administration of gatifloxacin drops for 3 days before injection, or no pretreatment antibiotics. Cultures were collected from the bulbar conjunctiva at the injection site and at the corresponding location in the fellow eye before PVI preparation. After topical PVI treatment and immediately before injection, a third culture was obtained at the injection site. Additionally, the injection needle was also cultured after the procedure.Incidence of positive bacterial samples collected from injection site conjunctiva and injection needles.Three-day gatifloxacin use resulted in a significantly lower rate of SeptiChek (Becton Dickinson, Franklin Lakes, NJ) positive cultures compared with untreated controls (21% vs 48% respectively, P = 0.005). After topical PVI, the rate of positive bacterial cultures in gatifloxacin-treated and control eyes were similar (8% and 4%, respectively; P = 0.324).Although 3-day topical gatifloxacin use is effective in reducing the frequency of conjunctival bacterial growth relative to untreated eyes, antibiotic use confers no additional benefit in combination with PVI than eyes receiving PVI alone. This supports that topical PVI is an effective preinjection monotherapy for infection prophylaxis in the setting of IVT injections.

    View details for DOI 10.1016/j.ophtha.2009.02.024

    View details for Web of Science ID 000268710200013

    View details for PubMedID 19501409

  • Prospective Randomized Comparison of 1-Day and 3-Day Application of Topical 0.5% Moxifloxacin in Eliminating Preoperative Conjunctival Bacteria JOURNAL OF OCULAR PHARMACOLOGY AND THERAPEUTICS He, L., Ta, C. N., Hu, N., Sinnar, S., de Kaspar, H. M. 2009; 25 (4): 373-378

    Abstract

    Compare the efficacy of a 1-day versus 3-day application of topical 0.5% moxifloxacin in reducing preoperative conjunctival bacteria.Following IRB approval, patients (n = 144) scheduled for ocular surgery between 2004 and 2005 were recruited and randomized to receive topical 0.5% moxifloxacin drops four times a day for either 1 day (n = 63) or 3 days (n = 57) prior to surgery. Conjunctival cultures were obtained at baseline (T0), after application of antibiotic (T1), following povidone-iodine and additional antibiotic applications immediately before surgery (T2), and after surgery (T3). Cultures were inoculated onto blood and chocolate agar plates and in thioglycolate broth, and then incubated at 37 degrees C for 10 days. Bacterial growth were isolated, identified, quantified, and compared.There were similar (P = 0.8435) rates of patients with positive thioglycolate cultures between the 1-day (79.37%) and 3-day groups (82.46%) at T0. At T1, T2, and T3, the number of eyes with positive cultures were again similar (1 day, 3 days, P value [T1: 34.9%, 35.1%, P = 0.8631; T2: 14.3%, 7%, P = 0.3245; T3: 7.9%, 3.5%, P = 0.5199]). No significant differences were found between the colony-forming units (CFU) of bacteria on solid agar media in 1-day and 3-day groups at any of the time points studied (P values: 0.1-0.8). Coagulase-negative Staphylococcus was the most commonly isolated (73.3% at baseline).In patients undergoing intraocular anterior segment surgery, 1-day and 3-day applications of topical 0.5% moxifloxacin appear to have similar efficacy in reducing perioperative conjunctival bacteria.

    View details for DOI 10.1089/jop.2008.0102

    View details for Web of Science ID 000268629800012

    View details for PubMedID 19492956

  • Bioactive interpenetrating polymer network hydrogels that support corneal epithelial wound healing JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A Myung, D., Farooqui, N., Zheng, L. L., Koh, W., Gupta, S., Bakri, A., Noolandi, J., Cochran, J. R., Frank, C. W., Ta, C. N. 2009; 90A (1): 70-81

    Abstract

    The development and characterization of collagen-coupled poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) interpenetrating polymer network hydrogels is described. Quantitative amino acid analysis and FITC-labeling of collagen were used to determine the amount and distribution of collagen on the surface of the hydrogels. The bioactivity of the coupled collagen was detected by a conformation-specific antibody and was found to vary with the concentration of collagen reacted to the photochemically functionalized hydrogel surfaces. A wound healing assay based on an organ culture model demonstrated that this bioactive surface supports epithelial wound closure over the hydrogel but at a decreased rate relative to sham wounds. Implantation of the hydrogel into the corneas of live rabbits demonstrated that epithelial cell migration is supported by the material, although the rate of migration and morphology of the epithelium were not normal. The results from the study will be used as a guide toward the optimization of bioactive hydrogels with promise in corneal implant applications such as a corneal onlay and an artificial cornea.

    View details for DOI 10.1002/jbm.a.32056

    View details for Web of Science ID 000266648700007

  • A prospective study determining the efficacy of topical 0.5% levofloxacin on bacterial flora of patients with chronic blepharoconjunctivitis GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Yactayo-Miranda, Y., Ta, C. N., He, L., Kreutzer, T. C., Nentwich, M. M., Kampik, A., de Kaspar, H. M. 2009; 247 (7): 993-998

    Abstract

    To determine the efficacy of conjunctival bacterial eradication following a 1-day, 3-day and 7-day application of topical 0.5% levofloxacin, with and without eyelid scrub, in patients with chronic blepharoconjunctivitis (CBC).Patients with CBC (n = 60) were prospectively randomized to three groups (n = 20 in each group): no antibiotic treatment, topical levofloxacin four times per day in both eyes, and eyelid scrub in addition to topical levovofloxacin four times a day in both eyes. Patients without CBC (n = 40) were enrolled as the negative control group. Cultures of the conjunctiva were obtained from both eyes at baseline, 1 day, 3 days, and 7 days following treatment.The most common bacteria isolated for all groups at baseline were coagulase-negative Staphylococcus. Eight patients did not complete the study. The remaining 52 patients with CBC had a significantly higher rate of positive thioglycolate broth cultures (94%) compared to a 58% positive culture rate in patient without CBC (P < 0.0001). Treatment with at least 3 days of topical antibiotic in patient with CBC resulted in a significant reduction (P < 0.05) in the number of thioglycolate positive cultures (or= 88%). Following a minimum of a 1-day application of antibiotic, the median colony-forming unit was 0-1 compared to 3-8 for eyes without antibiotic treatment (P < 0.05). Scrubbing of the eyelids did not provide further benefit compared to antibiotic treatment alone.CBC eyes have a significantly higher number of positive cultures than eyes without CBC. The application of topical 0.5% levofloxacin for at least 3 days provided a significant reduction in the number of positive cultures as well as the number of bacteria harbored on the conjunctival surface.

    View details for DOI 10.1007/s00417-009-1039-0

    View details for Web of Science ID 000266451600016

    View details for PubMedID 19205719

  • In vitro antibiotic susceptibility of preoperative normal conjunctival bacteria EYE Ta, C. N., He, L., De Kaspar, H. M. 2009; 23 (3): 559-560

    Abstract

    To determine the antibiotic susceptibility of preoperative conjunctival bacterial flora.Antibiotic susceptibility of conjunctival bacterial strains isolated from 142 patients undergoing intraocular surgery was determined using the Kirby-Bauer disc diffusion technique. chi(2) statistical analysis was performed.Among the 116 bacteria isolated, 95 (82%) were coagulase-negative staphylococci (CNS). Most (>75%) of them were susceptible to vancomycin, minocycline, aminoglycosides, gatifloxacin, levofloxacin, and moxifloxacin. Approximately one-half of CNS was resistant to erythromycin and azithromycin. Over 90% of streptococci were susceptible to levofloxacin, moxifloxacin, and gatifloxacin.Fluoroquinolones, specifically gatifloxacin, levofloxacin, and moxifloxacin continue to provide broad-spectrum coverage against common conjunctival bacterial flora.

    View details for DOI 10.1038/eye.2008.65

    View details for Web of Science ID 000264119500010

    View details for PubMedID 18356928

  • Comparison of One-Day Versus One-Hour Application of Topical Gatifloxacin in Eliminating Conjunctival Bacterial Flora OPHTHALMOLOGY Moss, J. M., Nguyen, D., Liu, Y. I., Singh, K., Montague, A., Egbert, P. R., de Kaspar, H. M., Ta, C. N. 2008; 115 (11): 2013-2016

    Abstract

    To compare efficacies of 1-day, 1-hour, and combined 1-day/1-hour preoperative topical gatifloxacin in eliminating conjunctival bacterial flora.Prospective, comparative case series.Sixty patients (120 eyes) scheduled to undergo anterior segment intraocular surgery at Stanford University Medical Center.Cultures were collected from the palpebral conjunctival sac at baseline and after 1 day (4 doses), 1 hour (3 doses), and 1 day/1 hour (7 doses) of gatifloxacin use.Incidence of positive bacterial samples collected pre- and post-antibiotic treatment and number of colony forming units (CFUs).SeptiChek (Becton Dickinson, Franklin Lakes, NJ) positive cultures significantly decreased from 67% growth at baseline to 28% (P<0.0001) after 1 day and from 60% at baseline to 37% (P = 0.018) after 1 hour of gatifloxacin use. Reductions of 44% growth at baseline to 12% (P = 0.0001) after 1 day and 32% at baseline to 13% (P = 0.029) after 1 hour of gatifloxacin use were observed on blood agar. Surgical eyes that received both 1-day and 1-hour preoperative gatifloxacin had reductions from 67% growth at baseline to 18% posttreatment (P<0.0001) and 45% at baseline to 7% posttreatment (P<0.0001) on SeptiChek and blood agar media, respectively. In addition to a lower frequency of positive cultures, a significantly lower CFU count was found after 1-day (P = 0.004) and 1-hour (P = 0.049) gatifloxacin use compared with pretreatment levels. Combined 1-day/1-hour doses of gatifloxacin were associated with a greater reduction in CFUs (P = 0.001) when compared with 1-hour treatment alone.Both 1-hour and 1-day topical gatifloxacin use are effective in reducing the frequency of conjunctival bacterial growth and the overall bacterial load as measured by CFUs, relative to baseline. Although a 1-hour pretreatment is associated with a reduction in bacterial growth, the combination of 1-day and 1-hour preoperative gatifloxacin dosing results in an even lower overall bacterial load, suggesting that the latter might be the preferred preoperative regimen for eyes undergoing anterior segment surgery.

    View details for DOI 10.1016/j.ophtha.2008.06.024

    View details for Web of Science ID 000260448900024

    View details for PubMedID 18708260

  • Prospective comparison of topical moxifloxacin in eliminating conjunctival bacterial flora following a one-day or one-hour application JOURNAL OF OCULAR PHARMACOLOGY AND THERAPEUTICS Ta, C. N., Chan, I., Dhatt, H. S., Paterno, J., Fisher, E., Singh, K., Montague, A., Egbert, P. R., Cockerham, G., de Kaspar, H. M. 2008; 24 (4): 427-431

    Abstract

    The aim of this study was to compare the efficacy of a 1-hour(h) versus 1-day application of topical moxifloxacin in eliminating conjunctival bacterial flora.In this prospective, nonrandomized, controlled trial, the surgical eyes of 60 patients scheduled for intraocular surgery received topical moxifloxacin four times a day, starting 1 day prior to surgery and three additional applications at 5-minute intervals 1 h before surgery. The nonsurgical eye of each patient only received three applications of the same antibiotic at 5-minute intervals 1 h before surgery. Conjunctival cultures were obtained at baseline and after antibiotic application.Prior to antibiotic application, 80% of surgical eyes and 70% of nonsurgical eyes had positive cultures. Following the 1-day application, significantly fewer eyes (40%) had positive cultures (P < 0.0001), with a further reduction to 32% with three additional doses 1 h prior to surgery. In the nonsurgical eye, the decrease in the percentage of positive cultures, from 55% to 53% following the three applications 1 h prior to surgery, was not significant (P > 0.9999). The 1-day application was associated with significantly fewer positive cultures, compared to the 1-h group (P = 0.0267).The one-day application of moxifloxacin resulted in significantly fewer positive conjunctival cultures, compared with a 1-h application.

    View details for DOI 10.1089/jop.2008.0018

    View details for Web of Science ID 000258731100011

    View details for PubMedID 18665815

  • Progress in the development of interpenetrating polymer network hydrogels POLYMERS FOR ADVANCED TECHNOLOGIES Myung, D., Waters, D., Wiseman, M., Duhamel, P., Noolandi, J., Ta, C. N., Frank, C. W. 2008; 19 (6): 647-657

    Abstract

    Interpenetrating polymer networks (IPNs) have been the subject of extensive study since their advent in the 1960s. Hydrogel IPN systems have garnered significant attention in the last two decades due to their usefulness in biomedical applications. Of particular interest are the mechanical enhancements observed in "double network" IPN systems which exhibit nonlinear increases in fracture properties despite being composed of otherwise weak polymers. We have built upon pioneering work in this field as well as in responsive IPN systems to develop an IPN system based on end-linked poly-(ethylene glycol) (PEG) and loosely crosslinked poly(acrylic acid) (PAA) with hydrogen bond-reinforced strain-hardening behavior in water and high initial Young's moduli under physiologic buffer conditions through osmotically induced pre-stress. Uniaxial tensile tests and equilibrium swelling measurements were used to study PEG/PAA IPN hydrogels having second networks prepared with varying crosslinking and photoinitiator content, pH, solids content, and comonomers. Studies involving the addition of non-ionic comonomers and neutralization of the second network showed that template polymerization appears to be important in the formation of mechanically enhanced IPNs.

    View details for DOI 10.1002/pat.1134

    View details for Web of Science ID 000257014100025

    View details for PubMedID 19763189

  • Bacterial contamination of ocular surface and needles in patients undergoing intravitreal injections RETINA-THE JOURNAL OF RETINAL AND VITREOUS DISEASES De Caro, J. J., Ta, C. N., Ho, H. V., Cabael, L., Hu, N., Sanislo, S. R., Blumenkranz, M. S., Moshfeghi, D. M., Jack, R., de Kaspar, H. M. 2008; 28 (6): 877-883

    Abstract

    To evaluate potential sources of bacterial contamination during intravitreal (IVT) injection procedures.Patients scheduled for IVT injection were asked to enroll in the study at the California Vitreoretinal Center (Menlo Park, CA) and the Vantage Eye Center (Salinas, CA) between October 2004 and April 2005. A total of 104 patients participated in the study, with a total of 118 IVT injection procedures performed on 107 eyes. Standard microbiological techniques were used to culture, identify, and quantify bacterial contamination of injection needles and the bulbar conjunctiva at the injection site in patients undergoing IVT injections. The main outcomes measured were type and quantity of bacterial isolates.Two (2%) of 114 needles collected were contaminated with bacteria. The prevalence of bacterial contamination of the injection site on the bulbar conjunctiva was 43% before prophylaxis on the day of the injection with topical antibiotics and povidone-iodine, with a statistically significant reduction to 13% after prophylaxis (P < 0.0001). Coagulase-negative Staphylococcus, the most common bacterium isolated from the ocular surface, was isolated from both culture-positive needles.IVT injection needles became contaminated with bacteria during the injection procedure. Although the contamination rate was low, this supports a mechanism of postinjection endophthalmitis in which there is direct inoculation of ocular surface flora into the vitreous cavity by the injection needle.

    View details for Web of Science ID 000256714300014

    View details for PubMedID 18536606

  • Development of hydrogel-based keratoprostheses: A materials perspective BIOTECHNOLOGY PROGRESS Myung, D., Duhamel, P., Cochran, J. R., Noolandi, J., Ta, C. N., Frank, C. W. 2008; 24 (3): 735-741

    Abstract

    Research and development of artificial corneas (keratoprostheses) in recent years have evolved from the use of rigid hydrophobic materials such as plastics and rubbers to hydrophilic, water-swollen hydrogels engineered to support not only peripheral tissue integration but also glucose diffusion and surface epithelialization. The advent of the AlphaCor core-and-skirt hydrogel keratoprosthesis has paved the way for a host of new approaches based on hydrogels and other soft materials that encompass a variety of materials preparation strategies, from synthetic homopolymers and copolymers to collagen-based bio-copolymers and, finally, interpenetrating polymer networks. Each approach represents a unique strategy toward the same goal: to develop a new hydrogel that mimics the important properties of natural donor corneas. We provide a critical review of these approaches from a materials perspective and discuss recent experimental results. While formidable technical hurdles still need to be overcome, the rapid progress that has been made by investigators with these approaches is indicative that a synthetic donor cornea capable of surface epithelialization is now closer to becoming a clinical reality.

    View details for DOI 10.1021/bp070476n

    View details for Web of Science ID 000256593300033

    View details for PubMedID 18422366

  • Effects of intravitreal corticosteroid in the treatment of Staphylococcus aureus-induced experimental endophthalmitis RETINA-THE JOURNAL OF RETINAL AND VITREOUS DISEASES De Kaspar, H. M., Ta, C. N., Engelbert, M., Mette, M., Thiel, M., Kampik, A. 2008; 28 (2): 326-332

    Abstract

    To investigate whether intravitreal injection of dexamethasone in addition to antibiotics can minimize intraocular tissue injury caused by Staphylococcus aureus endophthalmitis.Albino rabbits were infected with an intravitreal injection of 1000 colony-forming units of S. aureus. The rabbits were randomized to receive no treatment (control group; n = 2), intravitreal vancomycin and amikacin (n = 5), or a combination of intravitreal vancomycin, amikacin, and dexamethasone (n = 5) 20 hours following inoculation of bacteria. All rabbits except for the control group also received intravenous imipenem every 8 hours for 4 days. The eyes were evaluated by clinical examination, electroretinogram (ERG), and histologic studies.Eyes treated with intravitreal dexamethasone demonstrated less inflammation on clinical examination compared with eyes that received antibiotics alone. The ERG responses of eyes that received both intravitreal antibiotics and steroid were significantly better at 45 hours, 7 and 14 days following inoculation (P < 0.05) compared to eyes that received antibiotics alone. Histologic studies 14 days following infection demonstrated less tissue destruction for eyes treated with dexamethasone.Compared to intravitreal antibiotics alone, intravitreal corticosteroids may improve visual outcome of S. aureus endophthalmitis by reducing inflammation and preserving electrophysiologic retinal function.

    View details for Web of Science ID 000253460800018

    View details for PubMedID 18301039

  • Glucose-permeable interpenetrating polymer network hydrogels for corneal implant applications: A pilot study CURRENT EYE RESEARCH Myung, D., Farooqui, N., Waters, D., Schaber, S., Koh, W., Carrasco, M., Noolandi, J., Frank, C. W., Ta, C. N. 2008; 33 (1): 29-43

    Abstract

    Epithelialization of a keratoprosthesis requires that the implant material be sufficiently permeable to glucose. We have developed a poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) interpenetrating polymer network (IPN) hydrogel that can provide adequate passage of glucose from the aqueous humor to the epithelium in vivo. A series of PEG/PAA IPNs with varying PEG macromonomer molecular weights were synthesized and evaluated through swelling studies to determine their water content and diffusion experiments to assess their permeability to glucose. One of the PEG/PAA hydrogels prepared in this study had a glucose diffusion coefficient nearly identical to that of the human cornea (approximately 2.5 x 10(-6) cm(2)/sec). When implanted intrastromally in rabbit corneas, this hydrogel was retained and well-tolerated in 9 out of 10 cases for a period of 14 days. The retained hydrogels stayed optically clear and the epithelium remained intact and multilayered, indicating that the material facilitated glucose transport from the aqueous humor to the anterior part of the eye. The results from these experiments indicate that PEG/PAA hydrogels are promising candidates for corneal implant applications such as keratoprostheses and intracorneal lenses, and that the PEG/PAA IPN system in general is useful for creating permeable substrates for ophthalmic and other biomedical applications.

    View details for DOI 10.1080/02713680701793930

    View details for Web of Science ID 000252582500005

    View details for PubMedID 18214741

  • Prospective comparative evaluation of povidone-iodine (10% for 5 minutes versus 5% for 1 minute) as prophylaxis for ophthalmic surgery JOURNAL OF CATARACT AND REFRACTIVE SURGERY Ta, C. N., Singh, K., Egbert, P. R., de Kaspar, H. M. 2008; 34 (1): 171-172

    View details for DOI 10.1016/j.jcrs.2007.08.035

    View details for Web of Science ID 000252291100041

    View details for PubMedID 18165101

  • A prospective randomized study to determine the efficacy of preoperative topical levofloxacin in reducing conjunctival bacterial flora AMERICAN JOURNAL OF OPHTHALMOLOGY de Kaspar, H. M., Kreutzer, T. C., Aguirre-Romo, I., Ta, C. N., Dudichum, J., Bayrhof, M., Klauss, V., Kampik, A. 2008; 145 (1): 136-142

    Abstract

    To compare the efficacy of topical levofloxacin in combination with povidone-iodine irrigation vs povidone-iodine (PVI) alone in reducing conjunctival bacteria.Prospective, randomized, controlled trial.One hundred and forty eyes of 140 patients scheduled to undergo intraocular surgery eyes were randomized to either group 1 or 2 (70 each). Whereas group 1 eyes had no prophylactic antibiotic, eyes in group 2 received topical treatment with one drop of 0.5% levofloxacin four times on the day before surgery. Both groups underwent irrigation of the fornices with 1% PVI. Conjunctival swabs were inoculated on solid and broth culture media to determine bacterial growth.Of 132 eyes evaluated, baseline culture analysis in thioglycolate demonstrated positive culture results in 55 (84.6%) of 65 eyes from group 1, similar to 55 (82.1%) of 67 eyes in group 2 (P = .697). Before surgery, 57 (87.7%) of 65 eyes in group 1 had positive culture results, compared with 50 (74.6%) of 67 eyes in group 2 (P = .055). After irrigation with PVI, 20 (30.8 %) of 65 eyes in group 1 had positive culture results, compared with only eight (11.9%) of 67 eyes in group 2 (P = .008). After surgery, 15 (23.1%) of 65 eyes in group 1 and six (9.0%) of 67 eyes in group 2 had positive culture results (P = .027).Our study shows an enhanced effect of using topical levofloxacin in combination with PVI irrigation to reduce conjunctival bacteria in patients undergoing intraocular surgery.

    View details for DOI 10.1016/j.ajo.2007.08.031

    View details for Web of Science ID 000251980400020

    View details for PubMedID 17996212

  • Design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct BIOMEDICAL MICRODEVICES Myung, D., Koh, W., Bakri, A., Zhang, F., Marshall, A., Ko, J., Noolandi, J., Carrasco, M., Cochran, J. R., Frank, C. W., Ta, C. N. 2007; 9 (6): 911-922

    Abstract

    We describe the design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct, and demonstrate the adhesion of corneal epithelial and fibroblast cells to its central and peripheral components, respectively. The design consists of a central "core" optical component and a peripheral tissue-integrable "skirt." The core is composed of a poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) double-network with high strength, high water content, and collagen type I tethered to its surface. Interpenetrating the periphery of the core is a microperforated, but resilient poly(hydroxyethyl acrylate) (PHEA) hydrogel skirt that is also surface-modified with collagen type I. The well-defined microperforations in the peripheral component were created by photolithography using a mask with radially arranged chrome discs. Surface modification of both the core and skirt elements was accomplished through the use of a photoreactive, heterobifunctional crosslinker. Primary corneal epithelial cells were cultured onto modified and unmodified PEG/PAA hydrogels to evaluate whether the central optic material could support epithelialization. Primary corneal fibroblasts were seeded onto the PHEA hydrogels to evaluate whether the peripheral skirt material could support the adhesion of corneal stromal cells. Cell growth in both cases was shown to be contingent on the covalent tethering of collagen. Successful demonstration of cell growth on the two engineered components was followed by fabrication of core-skirt constructs in which the central optic and peripheral skirt were synthesized in sequence and joined by an interpenetrating diffusion zone.

    View details for DOI 10.1007/s10544-006-9040-4

    View details for Web of Science ID 000250462200017

    View details for PubMedID 17237989

  • Aspergillus fumigatus keratitis following laser in situ keratomileusis JOURNAL OF CATARACT AND REFRACTIVE SURGERY Sun, Y., Jain, A., Ta, C. N. 2007; 33 (10): 1806-1807

    Abstract

    A 31-year-old woman developed pain, decreased vision, and a corneal flap infiltrate 4 days following laser in situ keratomileusis (LASIK). Treatment with topical antibiotic agents did not improve the symptoms. Approximately 2 weeks after surgery, the patient was referred to Stanford University, with 20/400 visual acuity in the left eye and a stromal infiltrate posterior to the flap. Cultures demonstrated Aspergillus fumigatus sensitive to voriconazole. The corneal ulcer progressed despite aggressive antifungal treatment, requiring amputation of the corneal flap and daily debridement. The infiltrate resolved in response to topical voriconazole, natamycin, and oral voriconazole. Aspergillus fumigatus keratitis is a rare but serious complication of LASIK surgery. The infection was successfully treated with flap amputation and daily debridement in addition to antifungal therapy.

    View details for DOI 10.1016/j.jcrs.2007.05.051

    View details for Web of Science ID 000250100200037

    View details for PubMedID 17889780

  • Prospective randomized comparison of 1-day versus 3-day application of topical levofloxacin in eliminating conjunctival flora EUROPEAN JOURNAL OF OPHTHALMOLOGY Ta, C. N., Sinnar, S., He, L., Myling, D., De Kaspar, H. M. 2007; 17 (5): 689-695

    Abstract

    To compare efficacy of a 1-day versus 3-day application of topical levofloxacin in reducing ocular surface bacteria.In this prospective randomized controlled trial, 100 volunteer patients (50 per group) were assigned to receive topical 0.5% levofloxacin four times daily for 1 day or 3 days. Conjunctival cultures were obtained prior to (T0) and after the application of antibiotics (T1). Additionally, all patients received topical levofloxacin at 5-minute intervals for three applications (T2), followed by two drops of topical 5% povidone-iodine (T3). Conjunctival cultures were obtained at timepoints T2 and T3.A 1-day application of topical levofloxacin significantly reduced (p = 0.0004) the number of eyes with positive conjunctival cultures from 41 eyes (82%) to 23 eyes (46%). Similarly, a 3-day application significantly reduced (p = 0.0001) the positive culture rate from 37 eyes (74%) to 17 eyes (34%). Two drops of povidone-iodine further reduced the positive culture rate for both groups to 20% (10 eyes for each group). There was no significant difference in positive culture rate between the 1-day and 3-day groups at T0 (p = 0.4689), T1 (p = 0.3074), T2 (p = 0.6706), or T3 (p = 1.000).The application of topical 0.5% levofloxacin for 1 or 3 days significantly reduced the number of eyes with positive conjunctival cultures. The addition of 5% povidone-iodine further eliminated bacteria from the conjunctiva. The application of levofloxacin for 1 day appears to be as effective as a 3-day application.

    View details for Web of Science ID 000252360300001

    View details for PubMedID 17932841

  • Topical antibiotic prophylaxis in intraocular injections ARCHIVES OF OPHTHALMOLOGY Ta, C. N. 2007; 125 (7): 972-974

    View details for Web of Science ID 000247892600019

    View details for PubMedID 17620583

  • Prospective study demonstrating the efficacy of combined preoperative three-day application of antibiotics and povidone-lodine irrigation ANNALS OF OPHTHALMOLOGY Ta, C. N., Lin, R. C., Singh, G., de Kaspar, H. M. 2007; 39 (4): 313-317

    Abstract

    In 50 patients undergoing anterior segment intraocular surgery we determined that a three-day course of topical ofloxacin followed by preoperative povidone-iodine irrigation caused a marked decrease in the number of conjunctival bacterial flora and resulted in no contamination of the anterior chamber aqueous fluid at the beginning and conclusion of surgery.

    View details for Web of Science ID 000251199500008

    View details for PubMedID 18025652

  • Histological processing of pH-sensitive H93ydrogels used in corneal implant applications J. Histotechnology Farooqui N, Myung D, Koh K, Masek M, Dalal R, Carrasco MR, Noolandi N, Frank CW, Ta CN 2007; 30 (3): 157-163
  • Biomimetic strain hardening in interpenetrating polymer network hydrogels Polymer Myung D, Koh WG, Ko J, Hu Y, Carrasco M, Noolandi J, Ta CN, Frank CW 2007; 48 (18): 5376-5387
  • The effectiveness of the new fluoroquinolones against the normal bacterial flora of the conjunctiva OPHTHALMOLOGE Koss, M. J., Eder, M., Blumenkranz, M. S., Klauss, V., Ta, C. N., de Kaspar, H. M. 2007; 104 (1): 21-27

    Abstract

    Our aim was to determine the antibiotic susceptibility of the preoperative conjunctival bacterial flora against 25 commonly used antibiotics, especially the new fluoroquinolones levofloxacin, gatifloxacin, and moxifloxacin.The Kirby-Bauer disk-diffusion technique was used to test for the in vitro antibiotic susceptibility of conjunctival bacterial strains isolated from 160 patients (median=74 years, mean=71 years) undergoing cataract surgery at the Department of Ophthalmology, Stanford University, CA, USA.Among the 256 bacteria isolated, 201 (79%) were coagulase-negative staphylococci (CNS), 26 Staphylococcus aureus, 15 Streptococcus group D and 14 gram-negative rods. A total of 100 of these 256 strains (39%) were classified as multiresitant (resistant to>or=five antibiotics). The resistance rate (RR) of commonly used antibiotics for all CNS was: gatifloxacin=moxifloxacin

    View details for DOI 10.1007/s00347-006-1453-1

    View details for Web of Science ID 000243817700003

    View details for PubMedID 17160378

  • Endophthalmitis prophylaxis. Ophthalmology clinics of North America Ou, J. I., Ta, C. N. 2006; 19 (4): 449-456

    Abstract

    The prevalence of postoperative endophthalmitis following cataract surgery appears to be increasing with the popularity of clear cornea incision. As a result, endophthalmitis prophylaxis will play and increasingly important role as the number of clear cornea cataract surgeries increases. In this article, the authors examine and critically evaluate techniques used to prevent endophthalmitis including proper preoperative patient preparation, application of povidone-iodine, and use of broad-spectrum antibiotics (topical, intracameral, and subconjunctival injection).

    View details for PubMedID 17067900

  • Clinical results of topical fluconazole for the treatment of filamentous fungal keratitis GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Sonego-Krone, S., Sanchez-Di Martino, D., Ayala-Lugo, R., Torres-Alvariza, G., Ta, C. N., Barbosa, L., Mino De Kaspar, H. 2006; 244 (7): 782-787

    Abstract

    Fungal keratitis is a rare but serious condition that may result in loss of vision. The potentially poor prognosis might be due to a delay in diagnosis and/or to limited treatment options. The aim of this study is to evaluate the clinical outcome of patients treated with topical fluconazole 0.2% for the treatment of filamentous fungal keratitis.Retrospective case series. A chart review of all patients evaluated at the Ophthalmology Department of the Hospital de Clínicas in Paraguay from January 1997 to December 2000 identified 25 cases of fungal keratitis. Among these cases, one patient discontinued the treatment and another received amphotericin as the first line drug, resulting in 23 cases available for data analysis. Twelve patients were treated with topical fluconazole 0.2% alone (Group I) and 11 patients received a combination of topical fluconazole 0.2% and oral ketoconazole 200 mg twice daily (Group II).Sixteen of 23 cases showed resolution of the keratitis, 9/12 (75%) in Group I and 7/11 (64%) in Group II. Seven patients (30%) did not respond to medical treatment and required a surgical procedure to preserve eye integrity. Superficial and small ulcers have a significantly better prognosis than do lrge and deep ulcers. Concomitant oral ketoconazole (400 mg/day) did not improve the clinical results.Our findings of study suggest that topical fluconazole 0.2% is a safe and effective antifungal drug for the management of filamentous mycotic keratitis, particularly in cases that are not severe. The addition of oral ketoconazole to topical fluconazole did not improve the clinical outcome.

    View details for DOI 10.1007/s00417-005-1127-8

    View details for Web of Science ID 000239148000003

    View details for PubMedID 16133016

  • Prospective randomized study determining whether a 3-day application of ofloxacin results in the selection of fluoroquinolone-resistant coagulase-negative Staphylococcus EUROPEAN JOURNAL OF OPHTHALMOLOGY Ta, C. N., He, L., Nguyen, E., Mino De Kaspar, H. 2006; 16 (3): 359-364

    Abstract

    To determine whether a 3-day application of ofloxacin results in the selection of fluoroquinolone-resistant conjunctival coagulase-negative Staphylococcus.Prospective randomized trial.Patients scheduled for ocular surgery were randomized to a control (89 eyes) or study group (70 eyes). The study group received topical ofloxacin (0.3%) four times a day for 3 days. Conjunctival cultures were obtained at baseline (T0) and after 3 days of ofloxacin (T1). Cultures were also obtained at T0 and T1 for the control group, but these eyes did not receive an antibiotic. Bacteria isolated were identified and antibiotic susceptibility was determined.At T0, 53 out of 89 patients (60%) in the control and 48 out of 70 patients (69%) in the study group harbored coagulase-negative Staphylococcus. Among these coagulase-negative Staphylococcus, 12 out of 53 in the control and 11 out of 48 in the study group were resistant to ofloxacin (p>0.9999). At T1, significantly fewer coagulase-negative Staphylococcus (p=0.0003) were isolated from the study group (18 coagulase-negative Staphylococcus), compared the control group (48 coagulase-negative Staphylococcus). Of these, 5 out of 17 coagulase-negative Staphylococcus in the study group and 9 out of 48 coagulase-negative Staphylococcus in the control group were resistant to ofloxacin (p=0.5649). There was no significant difference in the number of coagulase-negative Staphylococcus resistant to ciprofloxacin or norfloxacin in the study group compared to the control group at T1.Ofloxacin given four times a day for 3 days does not select out for conjunctival fluoroquinolone-resistant coagulase-negative Staphylococcus.

    View details for Web of Science ID 000239306400001

    View details for PubMedID 16761235

  • Glucose permeability of human, bovine, and porcine corneas in vitro OPHTHALMIC RESEARCH Myung, D., Derr, K., Huie, P., Noolandi, J., Ta, K. P., Ta, C. N. 2006; 38 (3): 158-163

    Abstract

    To measure glucose flux across human, bovine, and porcine corneas and to determine the diffusion coefficient of each type of cornea.Diffusion of glucose across human (n = 8), bovine (n = 7), and pig corneas (n = 8) was measured using a modified blind well chamber apparatus (Boyden chamber). Dialysis membranes (n = 7) and nonporous Mylar membranes (n = 7) were used as positive and negative controls, respectively. Glucose concentrations were measured at 30-min intervals with a commercially available glucose meter.The diffusion of glucose through corneas in vitro was calculated by a simple Fickian diffusion model. The diffusion coefficient of glucose is highest for the human cornea (D(HC) = 3.0 +/- 0.2 x 10(-6) cm(2)/s) followed by porcine corneas (D(PC) = 1.8 +/- 0.6 x 10(-6) cm(2)/s) and bovine corneas (D(BC) = 1.6 +/- 0.1 x 10(-6) cm(2)/s) (p < 0.05). The diffusion coefficients of all tested corneas were significantly higher (p < 0.05) than that of dialysis membrane (D(DM) = 3.4 +/- 0.2 x 10(-7) cm(2)/s).The glucose diffusion coefficients of human, bovine, and porcine corneas are on the order of 10(-6). Human corneas have higher permeability to glucose than either porcine or bovine corneas.

    View details for DOI 10.1159/000090726

    View details for Web of Science ID 000238052500005

    View details for PubMedID 16401912

  • Normal ocular flora in newborns delivered in two hospital centers in Argentina and Paraguay GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Eder, M., Farina, N., Sanabria, R. R., Ta, C. N., Koss, M., Samudio, M., Cuevas, C., Gines, A., Simancas, M., Klauss, V., de Kaspar, H. M. 2005; 243 (11): 1098-1107

    Abstract

    To determine the spectrum of normal conjunctival flora in newborns in two hospital centers in North Argentina and Paraguay.In this prospective observational study, conjunctival specimens were obtained from the right eyes of newborns prior to the application of any topical medications. Culture samples were also obtained from the cervicovaginal secretions of the infants' mothers. All samples were directly inoculated into culture media and all growth were identified and quantified.Among the 190 newborns studied, 126 were delivered vaginally and 64 via caesarean section (C-section). A total of 180 different bacterial strains were acquired from the vaginally delivered infants and 77 from the C-section group (P=0.078, Student's t-test). Conjunctival cultures obtained within one hour of birth showed that 85 out of 101 samples (84%) from both the vaginal and C-section group had positive cultures, compared to 84 out of 89 samples (94%) obtained more than 1 h after birth (P<0.001). Among the vaginally delivered newborns, the most common bacteria isolated were coagulase-negative Staphylococcus (in 69 samples, 38%), Propionibacterium spp (36, 20%) and Corynebacterium spp (29, 16%). In the CES, the most common isolates were coagulase-negative Staphylococcus (39, 51%), Propionibacterium spp (22, 29%) and Staphylococcus aureus (6, 8%). There was a significantly higher proportion of gram-positive rods (P=0.017) isolated from infants delivered vaginally (16%) than from those delivered by C-section (5%). No Neisseria gonorrhoeae were isolated in conjunctival samples. Among the 130 organisms isolated from cervicovaginal secretions in 81 out of 189 mothers, the most common organisms were Lactobacillus spp. (47%), Corynebacterium spp (21%), Gardnerella vaginalis (15%), and Candida spp (14%). No Neisseria gonorrhoeae or Chlamydia trachomatis were found in cervicovaginal samples.The most common conjunctival bacteria in newborns delivered by either vaginal birth or C-section were coagulase-negative Staphylococcus. The proportion of positive conjunctival cultures was higher for infants delivered vaginally than for C-section delivery.

    View details for DOI 10.1007/s00417-004-1096-3

    View details for Web of Science ID 000234052000004

    View details for PubMedID 15912402

  • Use of rapid antibiotic susceptibility testing in bacterial endophthalmitis RETINA-THE JOURNAL OF RETINAL AND VITREOUS DISEASES Mino de Kaspar, H., Kreutzer, T. C., Ta, C. N., Kampik, A. 2005; 25 (3): 386-387

    View details for Web of Science ID 000241684400031

    View details for PubMedID 15805927

  • Antibiotic susceptibility of preoperative normal conjunctival bacteria AMERICAN JOURNAL OF OPHTHALMOLOGY de Kaspar, H. M., Koss, M. J., Blumenkranz, M. S., Ta, C. N. 2005; 139 (4): 730-733

    Abstract

    To determine the antibiotic susceptibility of preoperative conjunctival bacterial flora.In vitro study.Antibiotic susceptibility of conjunctival bacterial strains isolated from 164 patients undergoing intraocular surgery was determined using the Kirby-Bauer disk-diffusion technique.Among the 162 bacteria isolated, 124 (76%) were coagulase-negative staphylococci (CNS), with 2% resistant to gatifloxacin and moxifloxacin, and none were resistant to vancomycin or minocycline. Other bacteria isolated were 19 Staphylococcus aureus (S. aureus), 8 Streptococcus Group D, and 11 gram-negative rods. Most S. aureus (>85%) were susceptible to all antibiotics except for the penicillin and macrolide groups. No streptococci were resistant to gatifloxacin, levofloxacin, moxifloxacin, mezlocillin, imipenem, or vancomycin. None of the gram-negative rods were resistant to the fluoroquinolones. Approximately one half of all bacteria were resistant to erythromycin. One in three patients harbored multi-resistant bacteria (resistant to > or = five antibiotics).Newer-generation fluoroquinolones provide excellent broad-spectrum coverage against conjunctival bacterial flora.

    View details for Web of Science ID 000228222300031

    View details for PubMedID 15808182

  • Prospective Randomized comparison of 2 different methods of 5% povidone-lodine applications for anterior segment, Intraocular surgery ARCHIVES OF OPHTHALMOLOGY de Kaspar, H. M., Chang, R. T., Singh, K., Egbert, P. R., Blumenkranz, M. S., Ta, C. N. 2005; 123 (2): 161-165

    Abstract

    To determine the efficacy of reducing conjunctival bacteria flora with 2 different regimens of 5% povidone-iodine application: 2 drops on the conjunctiva cul-de-sac vs a 10-mL conjunctival irrigation of the fornices.In this prospective controlled trial, 200 eyes undergoing anterior segment intraocular surgery were randomized to control and study groups. All patients from both groups received topical ofloxacin and a povidone-iodine scrub of the periorbital area before the surgical procedure. The eyes in the control group received 2 drops of povidone-iodine on the conjunctiva preoperatively, whereas eyes in the study group had irrigation of the fornices with 10 mL of povidone-iodine. Conjunctival cultures were obtained at 4 separate time points before and after surgery.Twenty (26%) of 78 eyes in the study group had positive conjunctival cultures immediately prior to surgery compared with 40 (43%) of 94 eyes in the control group (P = .02). At the conclusion of the surgery, 14 (18%) of 78 eyes and 30 (32%) of 94 eyes had positive cultures in the study and control groups, respectively (P = .05).Irrigation of the fornices with 5% povidone-iodine was associated with significantly fewer positive conjunctival cultures at the time of surgery compared with the application of 2 drops on the conjunctiva.

    View details for Web of Science ID 000226755000002

  • Comparison of preoperative conjunctival bacterial flora in patients undergoing glaucoma or cataract surgery JOURNAL OF GLAUCOMA de Kaspar, H. M., Kreidl, K. O., Singh, K., Ta, C. N. 2004; 13 (6): 507-509

    Abstract

    To assess differences in conjunctival bacterial flora between patients undergoing glaucoma and cataract surgery.A prospective study comparing conjunctival bacterial cultures obtained from 339 patients undergoing either cataract (n = 258) or glaucoma (n = 81) surgery. All cultures were acquired during the preoperative visit, approximately three to seven days prior to surgery. The culture samples were inoculated onto blood and chocolate agar, as well as blood culture broth media. All bacterial isolates were identified and statistical analyses were performed to determine if there were differences in flora between the eyes undergoing cataract versus glaucoma surgery.Two hundred fifteen of 258 eyes (83%) undergoing cataract surgery were found to have positive bacterial growth, compared with 62 of 81 eyes (77%) of those undergoing glaucoma surgery (P = 0.2246). Coagulase-negative Staphylococci, the most common bacterial isolate, was cultured from 167 eyes (65%) in the cataract group and 42 (52%) in the glaucoma group (P = 0.0514). Among all bacterial isolates, only Corynebacterium species was found to be statistically different between the two patient groups with 92 (36%) and 11 (14%) eyes testing positive in the cataract and glaucoma groups, respectively (P = 0.0003).There was no statistically significant difference in the proportion of conjunctival culture samples testing positive for bacterial growth in eyes undergoing glaucoma surgery compared with those undergoing cataract surgery. Glaucoma medications, or their preservatives, do not appear to significantly alter conjunctival flora. Techniques used for endophthalmitis prophylaxis prior to cataract surgery are likely appropriate for glaucoma surgery as well.

    View details for Web of Science ID 000225273300014

    View details for PubMedID 15534478

  • Minimizing the risk of endophthalmitis following intravitreous injections RETINA-THE JOURNAL OF RETINAL AND VITREOUS DISEASES Ta, C. N. 2004; 24 (5): 699-705

    Abstract

    To review techniques that are important in preventing endophthalmitis following intravitreous injections based on the available evidence.A review of the literature regarding existing evidence that is relevant to post-injection endophthalmitis prophylaxis.The available evidence regarding endophthalmitis prophylaxis is largely based on intraocular surgery, particularly cataract surgery. Despite the controversy and the paucity of evidence regarding endophthalmitis prophylaxis for intravitreous injections, it is recommended that povidone-iodine should be used prior to intravitreous injections to minimize or eliminate the presence of ocular surface bacteria. Administration of topical antibiotics may also be considered before and after the intravitreous injections. Strict adherence to aseptic techniques, including the use of an eyelide speculum is also important.Endophthalmitic can occur following intravitreous injections. Prophylaxis with topical povidone-iodine, and possibly antibiotics, as well as adherence to aseptic technique may minimize the risk of post-injection endophthalmitis.

    View details for Web of Science ID 000224764100003

    View details for PubMedID 15492622

  • Evolving guidelines for intravitreous injections RETINA-THE JOURNAL OF RETINAL AND VITREOUS DISEASES Aiello, L. P., Brucker, A. J., Chang, S., Cunningham, E. T., D'Amico, D. J., Flynn, H. W., Grillone, L. R., Hutcherson, S., Liebmann, J. M., O'Brien, T. P., Scott, I. U., Spaide, R. F., Ta, C. 2004; 24 (5): S3-S19

    Abstract

    Intravitreous (i.v.t.) injection is increasingly being incorporated into the management of ocular diseases. While only fomivirsen sodium (Vitravene) is currently approved by the Food and Drug Administration as an i.v.t. injection, the number of approved i.v.t. injections indications is anticipated to grow on the basis of promising results from ongoing clinical studies. Despite the potential benefits that may be derived from intraocular injections of different agents, no guidelines have been published previously for i.v.t. injection. The purpose of this document is to identify specific strategies for the delivery of i.v.t. injection that may reduce risks and improve outcomes. Consensus was sought among a panel of investigators, surgeons experienced with this technique, and industry representatives. Objective evidence was sought for all guidelines, but consensus was accepted where evidence remains incomplete. In the absence of either evidence or consensus, the current manuscript identifies outstanding issues in need of further investigation. It is anticipated that more complete guidelines will evolve over time, potentially altering some of the guidelines included here, based on new applications of i.v.t. injection, additional clinical experience, and results of clinical trials.

    View details for Web of Science ID 000224828800002

    View details for PubMedID 15483476

  • Three-day application of topical ofloxacin reduces the contamination rate of microsurgical knives in cataract surgery - A prospective randomized study OPHTHALMOLOGY de Kaspar, H. M., Chang, R. T., Shriver, E. M., Singh, K., Egbert, P. R., Blumenkranz, M. S., Ta, C. N. 2004; 111 (7): 1352-1355

    Abstract

    To determine the rate of contamination of microsurgical knives during cataract surgery and the benefit of a 3-day versus a 1-hour preoperative application of topical ofloxacin in reducing the contamination rate.Prospective, randomized controlled trial.Seventy-eight eyes of 75 patients were randomly assigned to control (39 eyes) or study groups (39 eyes).All patients from both groups received 0.3% topical ofloxacin 1 hour before surgery, 5% povidone-iodine (PVI) scrub of the periorbital area, and 2 drops of PVI onto the ocular surface preoperatively. The patients in the study group also received ofloxacin 4 times a day for 3 days before surgery.Microsurgical knives were placed in blood culture broth media immediately after the incision had been made. The number of positive cultures and types of bacteria isolated were determined.Ten of 39 knives (26%) in the control group were found to be positive for bacterial growth compared with only 2 of 39 (5%) in the study group (P = 0.028).The initial paracentesis incision frequently results in contamination of the microsurgical knife and may serve as a mechanism for introducing bacteria from the ocular surface into the anterior chamber. The application of topical ofloxacin for 3 days before surgery significantly reduces the contamination rate of the microsurgical knives, compared with a preoperative application of ofloxacin given 1 hour before surgery.

    View details for Web of Science ID 000222418900017

    View details for PubMedID 15234136

  • Intravitreal vancomycin and amikacin versus intravenous imipenem in the treatment of experimental Staphylococcus aureus endophthalmitis GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Engelbert, M., de Kaspar, H. M., Thiel, M., Grasbon, T., Ta, C. N., Schulze-Schwering, M., Klauss, V., Kampik, A. 2004; 242 (4): 313-320

    Abstract

    Controversy still surrounds the intravenous (IV) treatment of endophthalmitis. The purpose of this study was to compare IV and intraocular (IO) treatment in experimental Staphylococcus aureus endophthalmitis: intravitreal injection of vancomycin and amikacin (VA/AN) in comparison with IV imipenem (IPM) and a combination of IV and IO (IV+IO) therapy.The right eyes of 27 rabbits were injected with 25000 S. aureus. After 24 h, animals were either treated with IO VA/AN ( n=5; 1.0 mg/0.4 mg in 0.1 ml saline), or IV IPM ( n=9; 37 mg/kg body weight 3x daily), or IV+IO therapy ( n=7), or served as untreated controls ( n=6). Clinical appearance was evaluated daily and vitreous aspirates were obtained for bacterial culture 24 h and 6 days after therapy, when the eyes were enucleated for histopathologic examination.Eyes in the IO or IO+IV treatment group had a significantly better appearance clinically and histologically than did eyes in the IV or untreated control group. Eyes in the IO+IV group had a similar appearance to the IO-treated eyes. All aspirates from the IO and IO+IV groups were culture-negative 24 hours after therapy, whereas only five of nine in the IV-treated group were culture-negative. Aspirates from all treatment groups were culture-negative by day 6 after the initiation of therapy. Untreated control eyes were culture-positive at all times.IO therapy with VA/AN proved more effective in treating experimental S. aureus endophthalmitis than did IV therapy with IPM alone. IV+IO treatment was not superior to IO treatment alone.

    View details for DOI 10.1007/s00417-003-0767-9

    View details for Web of Science ID 000221400000008

    View details for PubMedID 14986007

  • The challenge of determining aqueous contamination rate in anterior segment intraocular surgery AMERICAN JOURNAL OF OPHTHALMOLOGY Ta, C. N., Egbert, P. R., Singh, K., Blumenkranz, M. S., de Kaspar, H. M. 2004; 137 (4): 662-667

    Abstract

    To determine aqueous contamination rate in anterior segment intraocular surgery using two different techniques of obtaining aqueous fluid and to assess whether a 3-day application of topical 0.3% ofloxacin reduces this contamination rate compared with a 1-hour application.Randomized clinical trial.One hundred and thirty-three eyes of 130 patients undergoing anterior segment intraocular surgery were randomized to either control (64 eyes received topical ofloxacin 1 hour before surgery) or study groups (69 eyes received topical ofloxacin four times a day for 3 days before surgery in addition to 1 hour preoperatively). Eyes in both groups received a periorbital iodine scrub and two drops of topical 5% iodine. Aqueous fluid was obtained at the beginning and conclusion of surgery using a cannula passed through a paracentesis or a needle passed through clear cornea. The aqueous, cannula, and needles were inoculated in blood culture media broth and bacterial growth was identified.Overall, eight of 89 aqueous samples (9%) obtained using a cannula at the beginning of surgery were culture-positive. Similarly, six of 41 aqueous samples (15%) obtained through a needle through clear cornea at the beginning of surgery showed contamination. At the conclusion of surgery, nine of 112 samples (8%) showed positive cultures. There was no difference in the aqueous contamination rates between the control and study groups.Despite the use of a needle to obtain aqueous fluid at the beginning of surgery before creating a paracentesis, the aqueous contamination rate remained higher than that found at the conclusion of surgery. A 3-day application of topical ofloxacin before surgery did not reduce the anterior chamber aqueous contamination rate relative to a 1-hour application.

    View details for DOI 10.1016/j.ajo.2003.11.057

    View details for Web of Science ID 000220762800009

    View details for PubMedID 15059705

  • Epidemiological characteristics of microbiological results on patients with infectious corneal ulcers: a 13-year survey in Paraguay GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Laspina, F., Samudio, M., Cibils, D., Ta, C. N., Farina, N., Sanabria, R., Klauss, V., de Kaspar, H. M. 2004; 242 (3): 204-209

    Abstract

    This is a retrospective, chart-reviewed study of patients diagnosed with infectious corneal ulcers at the Ophthalmology Department of the National University of Asunción in Paraguay. The microbiological culture results are described, as well risk factors for the development of fungal keratitis.After obtaining approval from the Institutional Review Board, an analysis of medical charts from 1988 to 2001 was conducted and 660 patients were identified to have been diagnosed with infectious corneal ulcers due to bacteria or fungi. Demographic data were recorded, including age, gender, occupation and geographic location of their home and work (city or rural). Other information collected included the history of the presenting illness, past and current use of ocular medications and whether or not they had a history of trauma or contact lens use. Each patient had an eye examination performed by an ophthalmologist and corneal scrapings were obtained for cultures in all cases. Microbiologic culture results were analyzed.Twenty-one percent (136/660) of the specimens collected from the patients' conjunctiva and cornea were sterile in all culture media. Of the 524 (79%) positive cultures, 267 were due to bacteria (51%), 136 to fungi (26%), and 121 (23%) cultures yielded both fungi and bacteria. Of the 430 isolated bacteria approximately 25% (103) were coagulase negative Staphylococcus, followed by 23% (94) Staphylococcus aureus, 14% (60) Pseudomonas aeruginosa and 13% (56) Streptococcus pneumoniae. Acremonium species accounted for 40% (79) of all fungi identified, followed by Fusarium species (15%) (41). Approximately two-thirds of the patients were male (n = 435). For those patients for whom a history was available, approximately half had a history of trauma. Of these, half of these again involved foreign bodies. Over-the-counter medications were used commonly, and most of those patients had a delay in diagnosis of over 1 week. Risk factors for fungal keratitis as opposed to bacterial keratitis were male gender, agricultural occupation, age between 30 and 59, history of trauma and self-medication.The results of this study provide demographic data on patients with infectious corneal ulcers in Paraguay. Common causes of such ulcers are both bacteria and fungi. Most patients had self-medicated, and most had delayed seeking professional medical care.

    View details for DOI 10.1007/s00417-003-0808-4

    View details for Web of Science ID 000220563200003

    View details for PubMedID 14760489

  • Intravenous treatment of experimental Staphylococcus aureus endophthalmitis: imipenem versus the combination of ceftazidime and amikacin GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Engelbert, M., de Kaspar, H. M., Mette, M., Thiel, M., Ta, C. N., Grasbon, T., Schulze-Schwering, M., Klauss, V., Kampik, A. 2003; 241 (12): 1029-1036

    Abstract

    To compare the efficacy of intravenous (IV) imipenem (IPM) and a combination of IV ceftazidime (CAZ) and amikacin (AN) in the treatment of Staphylococcus aureus endophthalmitis in a rabbit model.Right eyes of 60 albino rabbits were injected with 1000 colony-forming units of S. aureus intravitreally. After 24 h, treatment with either IV IPM (37.5 mg/kg) every 8 h ( n=18) or IV CAZ (50 mg/kg) and AN (10 mg/kg) every 8 hours ( n=18) was begun and continued until the animals were killed at the indicated timepoints; 24 control animals received no treatment. The concentration of bacteria in the vitreous from six animals per group was determined microbiologically on days 2, 3, and 5 after infection, and histologic examination was performed on all eyes.The number of eyes with positive cultures on day 5 was lower in the group that received IV IPM (2/6) compared with the IV CAZ/AN group (4/6) and the control group (6/6). For the culture-positive eyes, the bacterial concentrations were significantly lower for the IV IPM group compared with the IV CAZ/AN group on days 2 and 5 ( P<0.05 and P<0.0065, respectively), but not on day 3 ( P <0.8. Bacterial counts in both treatment groups were significantly lower than in the control group ( P<0.005). Eyes in all groups, however, showed severe intraocular inflammation.IV IPM is more effective than is IV CAZ/AN in reducing the number of bacteria in an animal model of S.aureus endophthalmitis.

    View details for DOI 10.1007/s00417-003-0768-8

    View details for Web of Science ID 000188400600011

    View details for PubMedID 14618340

  • Antibiotic resistance patterns of ocular bacterial flora - A prospective study of patients undergoing anterior segment surgery OPHTHALMOLOGY Ta, C. N., Chang, R. T., Singh, K., Egbert, P. R., Shriver, E. M., Blumenkranz, M. S., de Kaspar, H. M. 2003; 110 (10): 1946-1951

    Abstract

    To determine the antibiotic susceptibility patterns of conjunctival bacterial flora isolated preoperatively from patients undergoing anterior segment surgery.Prospective observational study.One hundred fifty-six eyes from 139 patients scheduled for anterior segment surgery were enrolled over a 6-month period from August 2001 to February 2002.Conjunctival cultures were obtained on the day of surgery before povidone-iodine or antibiotic application.Bacterial isolates were identified and tested for antibiotic susceptibility using the Kirby-Bauer disc-diffusion technique.Among the 156 eyes studied, 36 were from patients who had undergone either bilateral surgery or more than one surgery in the same eye. Only the first eyes of the 120 patients that underwent initial ocular surgery were included in our analysis. Of these 120 eyes, 21 (18%) showed no bacterial growth. Of the 143 bacterial strains isolated from the remaining 99 eyes, 112 (78%) were coagulase-negative staphylococci (CNS). Among the CNS, greater than 90% were susceptible to cefotaxime, levofloxacin, imipenem, meropenem, vancomycin, and each of the aminoglycosides except neomycin. Between 70% and 90% of the CNS were susceptible to cefazolin, neomycin, ciprofloxacin, ofloxacin, norfloxacin, and chloramphenicol. Less than 70% of the isolated CNS were sensitive to the penicillin analogues, ceftazidime, erythromycin, and tetracycline.Preoperative conjunctival isolates of CNS seem to be most sensitive to vancomycin, the aminoglycosides (except neomycin), and levofloxacin.

    View details for DOI 10.1016/S0161-6420(03)00735-8

    View details for Web of Science ID 000185615400015

    View details for PubMedID 14522770

  • Risk factors for antibiotic-resistant conjunctival bacterial flora in patients undergoing intraocular surgery GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY de Kaspar, H. M., Shriver, E. M., Nguyen, E. V., Egbert, P. R., Singh, K., Blumenkranz, M. S., Ta, C. N. 2003; 241 (9): 730-733

    Abstract

    The purpose of this study was to determine if patients with certain risk factors are more likely to harbor conjunctival bacterial flora resistant to multiple antibiotics.In this prospective study, detailed medical history and slit-lamp examination were performed on all patients prior to intraocular surgery. Patients with local risk factors were defined as those with chronic blepharitis, conjunctivitis or discharge. Those with systemic risk factors were patients with diabetes, autoimmune, immunodeficient or skin disorders, asthma and those taking immunosuppressant medications. Conjunctival cultures were obtained prior to preoperative antibiotics and povidone-iodine. Bacteria isolated were identified and antibiotic susceptibility was determined. Bacteria resistant to five or more antibiotics were defined as multi-resistant (MR).Among the 207 patients enrolled in the study, 73 patients had local risk factors. Of these patients, 32 patients (44%) carried MR organisms, compared to 32 of the 134 patients (24%) without local risk factors (P=0.0049). Thirty-two of 71 patients (45%) with systemic risk factors harbored MR organisms, compared to 32 of 136 patients (24%) without systemic risk factors (P=0.0025). Seventeen of 93 patients (18%) who had neither local nor systemic risk factors had MR organisms on their conjunctiva. In contrast, 17 of the 30 patients (57%) with both local and systemic risk factors (57%) carried MR bacteria (P=0.0001).Patients with local and/or systemic risk factors are more likely to harbor MR organisms. This may be one mechanism for the reported increased risk of postoperative endophthalmitis in this group of patients.

    View details for DOI 10.1007/s00417-003-0742-5

    View details for Web of Science ID 000186037100008

    View details for PubMedID 12928904

  • Effects of minocycline on the ocular flora of patients with acne rosacea or seborrheic blepharitis CORNEA Ta, C. N., Shine, W. E., McCulley, J. P., Pandya, A., Trattler, W., Norbury, J. W. 2003; 22 (6): 545-548

    Abstract

    To assess the effect of minocycline on the ocular flora in patients with acne rosacea or blepharitis.A total of ten patients were enrolled in this prospective study, with six patients diagnosed with acne rosacea with concomitant meibomianitis, two patients with acne rosacea without concomitant ocular involvement, and two patients with seborrheic blepharitis. The eyelids and conjunctiva of both eyes were cultured before the initiation of systemic minocycline therapy, after 3 months of active therapy, and 3 months after the discontinuation of therapy. Isolated bacteria were identified and quantified, and antibiotic susceptibility was determined.The colony-forming units (CFU) isolated from the eyelids significantly decreased after a 3-month treatment with minocycline (P = 0.0013). The CFU significantly increased to approach that of the baseline with the discontinuation of minocycline (P = 0.0275). The most common isolated bacteria, including coagulase-negative Staphylococcus (CNS), Staphylococcus aureus (S. aureus), and Propionibacterium acne (P. acne), except for corynebacterium, had a significant decrease in bacterial count with minocycline therapy compared with baseline (P < 0.05). There was a trend in the decrease of bacterial CFU isolated from the conjunctiva with minocycline therapy, although this was not statistically significant (P = 0.1955). Four of the ten patients carried tetracycline-resistant CNS strains, but none of the S. aureus or P. acne isolated at baseline was resistant to tetracycline. All six patients with acne rosacea and concomitant meibomianitis had marked clinical improvement.Minocycline effectively decreased eyelid bacterial flora in patients with acne rosacea or blepharitis. One of the mechanisms of newer generation tetracycline analogues may be a decrease or elimination of bacterial flora from the eyelids.

    View details for Web of Science ID 000184750700011

    View details for PubMedID 12883348

  • Preoperative ofloxacin: author reply Ophthalmology Ta CN, Egbert PR, Singh K, Blumenkranz MS, Mino de Kaspar H 2003; 110 (12): 2431-1432
  • Nodular scleritis in a patient with pyoderma gangrenosum ARCHIVES OF OPHTHALMOLOGY Braun, M. M., Wong, I. G., Ta, C. N. 2002; 120 (12): 1763-1765

    View details for Web of Science ID 000179737900027

    View details for PubMedID 12470160

  • Prospective randomized comparison of 3-day versus 1-hour preoperative ofloxacin prophylaxis for cataract surgery OPHTHALMOLOGY Ta, C. N., Egbert, P. R., Singh, K., Shriver, E. M., Blumenkranz, M. S., de Kaspar, H. M. 2002; 109 (11): 2036-2040

    Abstract

    To determine the efficacy of reducing conjunctival bacterial flora with topical ofloxacin when given for 3 days compared with 1 hour before surgery.Prospective, randomized, controlled trial.Ninety-two eyes from 89 patients were randomized to a control group (48 eyes) or study group (44 eyes).All patients from both groups received topical ofloxacin 0.3% 1 hour before surgery and a 5% povidone iodine scrub of the periorbital area before surgery. The patients in the study group received additional ofloxacin four times daily for 3 days before surgery.Conjunctival cultures were obtained at five separate time points and were inoculated in solid and liquid culture media. The presence of bacteria was determined, quantified, and identified.Forty-two percent of eyes in the control group had positive conjunctival culture immediately before surgery, compared with 19% of eyes in the study group (P < 0.05). Immediately after surgery, 34% and 14% of eyes had positive cultures in the control and study groups, respectively (P < 0.05). Quantitatively, fewer bacteria were isolated from eyes in the study group compared with those in the control group for culture samples that were obtained both before povidone iodine scrub and at the conclusion of surgery (P

    View details for Web of Science ID 000178778600032

    View details for PubMedID 12414411

  • Evaluation and management of herpes zoster ophthalmicus AMERICAN FAMILY PHYSICIAN Shaikh, S., Ta, C. N. 2002; 66 (9): 1723-1730

    Abstract

    Herpes zoster ophthalmicus occurs when the varicella-zoster virus is reactivated in the ophthalmic division of the trigeminal nerve. Herpes zoster ophthalmicus represents up to one fourth of all cases of herpes zoster. Most patients with herpes zoster ophthalmicus present with a periorbital vesicular rash distributed according to the affected dermatome. A minority of patients may also develop conjunctivitis, keratitis, uveitis, and ocular cranial-nerve palsies. Permanent sequelae of ophthalmic zoster infection may include chronic ocular inflammation, loss of vision, and debilitating pain. Antiviral medications such as acyclovir, valacyclovir, and famcidovir remain the mainstay of therapy and are most effective in preventing ocular involvement when begun within 72 hours after the onset of the rash. Timely diagnosis and management of herpes zoster ophthalmicus. with referral to an ophthalmologist when ophthalmic involvement is present, are critical in limiting visual morbidity.

    View details for Web of Science ID 000179228500010

    View details for PubMedID 12449270

  • Intravenous imipenem prophylaxis in experimental endophthalmitis GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY de Kaspar, H. M., Engelbert, M., Thiel, M., Grasbon, T., Ta, C. N., Klauss, V., Kampik, A. 2002; 240 (7): 557-564

    Abstract

    To determine the effect of prophylactic intravenous imipenem on experimental Staphylococcus aureusendophthalmitis.The right eyes of 36 New Zealand albino rabbits received an intraocular injection of 100, 1,000, or 10,000 colony-forming units (CFU) of S. aureus. Each of these three groups was subdivided into a control group (no antibiotic prophylaxis) and a prophylactic group, which received 37.5 mg/kg imipenem 8 h prior to inoculation of bacteria, 30 min prior to inoculation of bacteria, and 8 h after inoculation of bacteria. Eyes were observed daily by slit-lamp examination and funduscopy. The eyes were enucleated after 5 and 9 days for the control and prophylactic groups, respectively. Vitreous samples were cultured for bacteria, and the eyes were prepared for histologic evaluation.All eyes that received imipenem demonstrated significantly less inflammation (two-way analysis of variance; P<0.001) on clinical examinations than did control eyes. The prophylactic groups that had received 100 CFU and 1,000 CFU of bacteria also had significantly fewer positive vitreous cultures than the corresponding controls (chi(2) test; P<0.001 and P<0.01, respectively). Histologically, the prophylactic groups injected with 100 CFU and 1,000 CFU of bacteria had significantly less inflammation than the control groups (Student's t-test; P<0.00001 and P<0.0001, respectively). There was no significant difference in the number of positive vitreous cultures or histologically between the control and prophylactic groups that received 10,000 CFU of bacteria.Prophylactic intravenous imipenem can prevent or significantly reduce the severity of experimental endophthalmitis.

    View details for DOI 10.1007/s00417-002-0490-y

    View details for Web of Science ID 000177433600011

    View details for PubMedID 12136287

  • Bilateral Mycobacterium abscessus keratitis after laser in situ keratomileusis JOURNAL OF CATARACT AND REFRACTIVE SURGERY Giaconi, J., Pham, R., Ta, C. N. 2002; 28 (5): 887-890

    Abstract

    A 35-year-old man was diagnosed with Mycobacterium abscessus keratitis in the left eye 3 weeks after bilateral laser in situ keratomileusis (LASIK). Infection in the right eye developed 6 weeks after surgery. Despite aggressive treatment with topical amikacin and clarithromycin and oral clarithromycin, the infection progressed in both eyes. To improve antibiotic penetration, the LASIK flap was removed in both eyes. Culture positivity was prolonged; however, after 8 weeks of intensive topical antibiotics, the infection was eradicated. The final best corrected visual acuity was 20/30 in both eyes.

    View details for Web of Science ID 000175281000034

    View details for PubMedID 11978473

  • Leber hereditary optic neuropathy associated with antiretroviral therapy for human immunodeficiency virus infection AMERICAN JOURNAL OF OPHTHALMOLOGY Shaikh, S., Ta, C., Basham, A. A., Mansour, S. 2001; 131 (1): 143-145

    Abstract

    Antiretroviral therapy has reduced the morbidity and mortality associated with human immunodeficiency virus (HIV) infection. However, side effects are increasingly recognized, including a commonly reported toxic mitochondrial myopathy. We report such a case of Leber hereditary optic neuropathy in a patient with antiretroviral therapy for HIV infection and speculate on a possible toxic etiologic role in the development of Leber hereditary optic neuropathy by a shared mitochondrial mechanism.Case Report. Bilateral optic disk abnormalities observed in a 38-year-old HIV positive man with a family history of Leber hereditary optic neuropathy were documented with fundus photography, color vision testing, and visual field testing. Mitochondrial DNA testing was used to confirm the genetic predisposition to Leber hereditary optic neuropathy.Progressive bilateral optic nerve pallor temporally associated with the administration of antiretroviral medication was observed. Diagnostic testing revealed progressive visual field and color vision loss as well as a mitochondrial DNA mutation consistent with Leber hereditary optic neuropathy.Antiretroviral therapy may be associated with the onset of Leber hereditary optic neuropathy in genetically predisposed patients.

    View details for Web of Science ID 000166429600028

    View details for PubMedID 11162998

  • Hyphema caused by a metallic intraocular foreign body during magnetic resonance imaging AMERICAN JOURNAL OF OPHTHALMOLOGY Ta, C. N., Bowman, R. W. 2000; 129 (4): 533-534

    Abstract

    To report a 63-year-old man with a retained intraocular foreign body who developed a hyphema during magnetic resonance imaging (MRI) of the brain.Case report and review of the current literature on ocular injury caused by intraocular foreign bodies when subjected to an electromagnetic field.Our patient underwent a brain MRI, and the intraocular foreign body caused a hyphema and increased intraocular pressure. The presence and location of the intraocular foreign body were determined by computed tomography (CT).Magnetic resonance imaging can cause serious ocular injury in patients with ferromagnetic intraocular foreign bodies. This case demonstrates the importance of obtaining an occupational history, and, when indicated, a skull x-ray or CT to rule out intraocular foreign body before an MRI study.

    View details for Web of Science ID 000086471800020

    View details for PubMedID 10764867

  • CONSTITUTIVE MUTATIONS OF AGROBACTERIUM-TUMEFACIENS TRANSCRIPTIONAL ACTIVATOR VIRG JOURNAL OF BACTERIOLOGY Pazour, G. J., Ta, C. N., Das, A. 1992; 174 (12): 4169-4174

    Abstract

    The virulence (vir) genes of Agrobacterium tumefaciens Ti plasmids are positively regulated by virG in conjunction with virA and plant-derived inducing molecules. A procedure that utilizes both genetic selection and a genetic screen was developed to isolate mutations in virG that led to elevated levels of vir gene expression in the absence of virA and plant phenolic inducers. Mutants were isolated at a frequency of 1 in 10(7) to 10(8). Substitution mutations at two positions in the virG coding region were found to result in the desired phenotype. One mutant had an asparagine-to-aspartic acid substitution at residue 54, and the other contained an isoleucine-to-leucine substitution at residue 106. In both cases, the mutant phenotype required the presence of the active-site aspartic acid residue at position 52. Further analysis showed that no other substitution at residue 54 resulted in a constitutive phenotype. In contrast, several substitutions at residue 106 led to a constitutive phenotype. The possible roles of the residues at positions 54 and 106 in VirG function are discussed.

    View details for Web of Science ID A1992HY09300041

    View details for PubMedID 1597431

  • MUTANTS OF AGROBACTERIUM-TUMEFACIENS WITH ELEVATED VIR GENE-EXPRESSION PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Pazour, G. J., Ta, C. N., Das, A. 1991; 88 (16): 6941-6945

    Abstract

    Expression of Agrobacterium tumefaciens virulence (vir) genes requires virA, virG, and a plant-derived inducing compound such as acetosyringone. To identify the critical functional domains of virA and virG, a mutational approach was used. Agrobacterium A136 harboring plasmid pGP159, which contains virA, virG, and a reporter virB:lacZ gene fusion, was mutagenized with UV light or nitrosoguanidine. Survivors that formed blue colonies on a plate containing 5-bromo-4-chloro-3-indolyl beta-D-galactoside were isolated and analyzed. Quantification of beta-galactosidase activity in liquid assays identified nine mutant strains. By plasmid reconstruction and other procedures, all mutations mapped to the virA locus. These mutations caused an 11- to 560-fold increase in the vegetative level of virB:lacZ reporter gene expression. DNA sequence analysis showed that the mutations are located in four regions of VirA: transmembrane domain one, the active site, a glycine-rich region with homology to ATP-binding sites, and a region at the C terminus that has homology to the N terminus of VirG.

    View details for Web of Science ID A1991GB70100009

    View details for PubMedID 1908084

Conference Proceedings


  • Rapid direct antibiotic susceptibility testing in endophthalmitis de Kaspar, H. M., Neubauer, A. S., Molnar, A., Hoepfner, A. S., Ta, C. N., Grasbon, T., Engelbert, M., Thiel, M., Klauss, V., Kampik, A. ELSEVIER SCIENCE INC. 2002: 687-693

    Abstract

    To compare a new rapid antibiotic susceptibility test (RAST) to the conventional method in patients with endophthalmitis.Prospective nonrandomized comparative trial.Intraocular aspirates from 24 consecutive patients with endophthalmitis were tested.Approximately 0.25 ml of vitreous or anterior chamber aspirate was obtained and tested for antibiotic sensitivity using the Kirby-Bauer agar disk diffusion method. Using this conventional testing method, the aspirates were cultured for bacterial growth before antibiotic susceptibility testing (AST). In contrast, for direct RAST, the aspirates were inoculated directly onto agar plates with antibiotic disks without first culturing for bacterial growth.Of the 24 endophthalmitis aspirates studied, 4 (17%) could not be tested by direct RAST because either more than one bacterial species was present or no bacteria were cultured. The remaining 20 cases provided 467 antibiotic-microorganism combinations. The two methods yielded identical susceptibility results in 409 (88%) of the 467 tests. In 42 tests (9%), a minor discrepancy occurred between the conventional method and RAST, in which one resulted in intermediate susceptibility, whereas the other was either resistant or sensitive. Significant discrepancy, defined as a bacterial sample reported as sensitive in one method yet resistant in the other, occurred with 16 samples (3%). Results of the RAST were available within 6 to 10 hours compared with more than 24 hours for the conventional method. Of clinical significance, the results of the RAST revealed that in 11 cases of epidemic Stenotrophomonas maltophilia endophthalmitis, the bacteria were resistant to the antibiotics prescribed, and change of antibiotic therapy was made on the basis of the RAST results.RAST provided accurate antibiotic susceptibility results in a much shorter time than did the conventional method. We suggest that conventional AST be performed for confirmation of the RAST results, but initial antibiotic therapy can quite reliably be based on the results of RAST.

    View details for Web of Science ID 000174636000027

    View details for PubMedID 11927425

  • Antibiotic resistance pattern and visual outcome in experimentally-induced Staphylococcus epidermidis endophthalmitis in a rabbit model de Kaspar, H. M., Hoepfner, A. S., Engelbert, M., Thiel, M., Ta, C. N., Mette, M., Schulze-Schwering, M., Grasbon, T., Sesma-Vea, B., Casas, J. M., Iturralde-Goni, R., Klauss, V., Kampik, A. ELSEVIER SCIENCE INC. 2001: 470-478

    Abstract

    To study whether the clinical outcome of Staphylococcus epidermidis-induced endophthalmitis in rabbits is related to the antibiotic resistance pattern of the infecting strain.Experimental animal study.The right eyes of 36 New Zealand white albino rabbits were inoculated with strains of S. epidermidis that displayed various patterns of antibiotic resistance.There were 12 rabbits in each of three study groups: fully antibiotic susceptible (FS), partially antibiotic resistant (PR), and multiresistant (MR). Five days after inoculation, the eyes were enucleated and prepared for histologic studies.Comparisons among the three groups were made based on electroretinographic (ERG) findings, histologic evaluation by a masked observer, and clinical examination.Electroretinographic findings on all rabbits were made by an unmasked observer. At 30 hours after inoculation, the ERG was diminished to 65% of normal for group FS, compared with a flat ERG waveform for groups PR (P < 0.05) and MR (P < 0.05). The ERG waveform was flat for all three groups at 72 hours after inoculation. Histologic evaluation by use of a histologic score revealed that the degree of inflammation and destruction of the retina was less for group FS (n = 10) compared with groups PR (n = 8) and MR (n = 8). Clinical examination revealed that there was a trend of less ocular inflammation for group FS compared with groups PR and MR.In a rabbit model of S. epidermidis-induced endophthalmitis, antibiotic-susceptible strains caused less inflammation and destruction of the infected retina than did antibiotic-resistant strains.

    View details for Web of Science ID 000167135200023

    View details for PubMedID 11237900

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