Recent Publications

Associate Professor of Ophthalmology and, by courtesy, of Chemical Engineering

Publications

  • Electrospun Nanofiber Membrane for Cultured Corneal Endothelial Cell Transplantation. Bioengineering (Basel, Switzerland) Song, E., Chen, K. M., Margolis, M. S., Wungcharoen, T., Koh, W., Myung, D. 2024; 11 (1)

    Abstract

    The corneal endothelium, comprising densely packed corneal endothelial cells (CECs) adhering to Descemet's membrane (DM), plays a critical role in maintaining corneal transparency by regulating water and ion movement. CECs have limited regenerative capacity within the body, and globally, there is a shortage of donor corneas to replace damaged corneal endothelia. The development of a carrier for cultured CECs may address this worldwide clinical need. In this study we successfully manufactured a gelatin nanofiber membrane (gelNF membrane) using electrospinning, followed by crosslinking with glutaraldehyde (GA). The fabricated gelNF membrane exhibited approximately 80% transparency compared with glass and maintained a thickness of 20 m. The gelNF membrane demonstrated desirable permeability and degradability for a Descemet's membrane analog. Importantly, CECs cultured on the gelNF membrane at high densities showed no cytotoxic effects, and the expression of key CEC functional biomarkers was verified. To assess the potential of this gelNF membrane as a carrier for cultured CEC transplantation, we used it to conduct Descemet's membrane endothelial keratoplasty (DMEK) on rabbit eyes. The outcomes suggest this gelNF membrane holds promise as a suitable carrier for cultured CEC transplantation, offering advantages in terms of transparency, permeability, and sufficient mechanical properties required for successful transplantation.

    View details for DOI 10.3390/bioengineering11010054

    View details for PubMedID 38247931

  • Embedded 3d Bioprinting of Collagen Inks into Microgel Baths to control hydrogel Microstructure and Cell Spreading. Advanced healthcare materials Brunel, L. G., Christakopoulos, F., Kilian, D., Cai, B., Hull, S. M., Myung, D., Heilshorn, S. C. 2023: e2303325

    Abstract

    Microextrusion-based 3D bioprinting into support baths has emerged as a promising technique to pattern soft biomaterials into complex, macroscopic structures. We hypothesized that interactions between inks and support baths, which are often composed of granular microgels, could be modulated to control the microscopic structure within these macroscopic-printed constructs. Using printed collagen bioinks crosslinked either through physical self-assembly or bioorthogonal covalent chemistry, we demonstrate that microscopic porosity is introduced into collagen inks printed into microgel support baths but not bulk gel support baths. The overall porosity is governed by the ratio between the ink's shear viscosity and the microgel support bath's zero-shear viscosity. By adjusting the flow rate during extrusion, the ink's shear viscosity was modulated, thus controlling the extent of microscopic porosity independent of the ink composition. For covalently crosslinked collagen, printing into support baths comprised of gelatin microgels (15-50 µm) resulted in large pores (∼40 µm) that allowed human corneal mesenchymal stromal cells to readily spread, while control samples of cast collagen or collagen printed in non-granular support baths did not allow cell spreading. Taken together, these data demonstrate a new method to impart controlled microscale porosity into 3D printed hydrogels using granular microgel support baths. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/adhm.202303325

    View details for PubMedID 38134346

  • AI-Human Hybrid Workflow Enhances Teleophthalmology for the Detection of Diabetic Retinopathy. Ophthalmology science Dow, E. R., Khan, N. C., Chen, K. M., Mishra, K., Perera, C., Narala, R., Basina, M., Dang, J., Kim, M., Levine, M., Phadke, A., Tan, M., Weng, K., Do, D. V., Moshfeghi, D. M., Mahajan, V. B., Mruthyunjaya, P., Leng, T., Myung, D. 2023; 3 (4): 100330

    Abstract

    Detection of diabetic retinopathy (DR) outside of specialized eye care settings is an important means of access to vision-preserving health maintenance. Remote interpretation of fundus photographs acquired in a primary care or other nonophthalmic setting in a store-and-forward manner is a predominant paradigm of teleophthalmology screening programs. Artificial intelligence (AI)-based image interpretation offers an alternative means of DR detection. IDx-DR (Digital Diagnostics Inc) is a Food and Drug Administration-authorized autonomous testing device for DR. We evaluated the diagnostic performance of IDx-DR compared with human-based teleophthalmology over 2 and a half years. Additionally, we evaluated an AI-human hybrid workflow that combines AI-system evaluation with human expert-based assessment for referable cases.Prospective cohort study and retrospective analysis.Diabetic patients ≥ 18 years old without a prior DR diagnosis or DR examination in the past year presenting for routine DR screening in a primary care clinic.Macula-centered and optic nerve-centered fundus photographs were evaluated by an AI algorithm followed by consensus-based overreading by retina specialists at the Stanford Ophthalmic Reading Center. Detection of more-than-mild diabetic retinopathy (MTMDR) was compared with in-person examination by a retina specialist.Sensitivity, specificity, accuracy, positive predictive value, and gradability achieved by the AI algorithm and retina specialists.The AI algorithm had higher sensitivity (95.5% sensitivity; 95% confidence interval [CI], 86.7%-100%) but lower specificity (60.3% specificity; 95% CI, 47.7%-72.9%) for detection of MTMDR compared with remote image interpretation by retina specialists (69.5% sensitivity; 95% CI, 50.7%-88.3%; 96.9% specificity; 95% CI, 93.5%-100%). Gradability of encounters was also lower for the AI algorithm (62.5%) compared with retina specialists (93.1%). A 2-step AI-human hybrid workflow in which the AI algorithm initially rendered an assessment followed by overread by a retina specialist of MTMDR-positive encounters resulted in a sensitivity of 95.5% (95% CI, 86.7%-100%) and a specificity of 98.2% (95% CI, 94.6%-100%). Similarly, a 2-step overread by retina specialists of AI-ungradable encounters improved gradability from 63.5% to 95.6% of encounters.Implementation of an AI-human hybrid teleophthalmology workflow may both decrease reliance on human specialist effort and improve diagnostic accuracy.Proprietary or commercial disclosure may be found after the references.

    View details for DOI 10.1016/j.xops.2023.100330

    View details for PubMedID 37449051

    View details for PubMedCentralID PMC10336195

  • Artificial Intelligence Improves Patient Follow-Up in a Diabetic Retinopathy Screening Program. Clinical ophthalmology (Auckland, N.Z.) Dow, E. R., Chen, K. M., Zhao, C. S., Knapp, A. N., Phadke, A., Weng, K., Do, D. V., Mahajan, V. B., Mruthyunjaya, P., Leng, T., Myung, D. 2023; 17: 3323-3330

    Abstract

    We examine the rate of and reasons for follow-up in an Artificial Intelligence (AI)-based workflow for diabetic retinopathy (DR) screening relative to two human-based workflows.A DR screening program initiated September 2019 between one institution and its affiliated primary care and endocrinology clinics screened 2243 adult patients with type 1 or 2 diabetes without a diagnosis of DR in the previous year in the San Francisco Bay Area. For patients who screened positive for more-than-mild-DR (MTMDR), rates of follow-up were calculated under a store-and-forward human-based DR workflow ("Human Workflow"), an AI-based workflow involving IDx-DR ("AI Workflow"), and a two-step hybrid workflow ("AI-Human Hybrid Workflow"). The AI Workflow provided results within 48 hours, whereas the other workflows took up to 7 days. Patients were surveyed by phone about follow-up decisions.Under the AI Workflow, 279 patients screened positive for MTMDR. Of these, 69.2% followed up with an ophthalmologist within 90 days. Altogether 70.5% (N=48) of patients who followed up chose their location based on primary care referral. Among the subset of patients that were seen in person at the university eye institute under the Human Workflow and AI-Human Hybrid Workflow, 12.0% (N=14/117) and 11.7% (N=12/103) of patients with a referrable screening result followed up compared to 35.5% of patients under the AI Workflow (N=99/279; χ2df=2 = 36.70, p < 0.00000001).Ophthalmology follow-up after a positive DR screening result is approximately three-fold higher under the AI Workflow than either the Human Workflow or AI-Human Hybrid Workflow. Improved follow-up behavior may be due to the decreased time to screening result.

    View details for DOI 10.2147/OPTH.S422513

    View details for PubMedID 38026608

    View details for PubMedCentralID PMC10665027

  • SCONE: Development of optic nerve head delivery technology Chiang, B., Dalal, R., Heng, K., Liao, Y., Goldberg, J. L., Myung, D. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2023
  • Real world outcomes from artificial intelligence to detect diabetic retinopathy in the primary care setting: 12 month experience Knapp, A. N., Dow, E., Chen, K., Khan, N. C., Do, D. V., Mahajan, V., Mruthyunjaya, P., Leng, T., Myung, D. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2023
  • Impact of crosslinking chemistry on corneal tissue regeneration after in situforming collagen-hyaluronate matrix therapy Wungcharoen, T., Chen, F., Seo, Y., Myung, D. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2023
  • Automated Detection of Dysthyroid Optic Neuropathy in Graves' Ophthalmopathy with Computed Tomography (CT) Scans by Convolutional Neural Networks Hung, J., Luo, A., Deng, Y., Chung, C., Fuh, C., Perera, C., Myung, D., Kossler, A., Liao, S. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2023
  • Collagen Gels Crosslinked by Photoactivation of Riboflavin for the Repair and Regeneration of Corneal Defects. ACS applied bio materials Fernandes-Cunha, G. M., Brunel, L. G., Arboleda, A., Manche, A., Seo, Y. A., Logan, C., Chen, F., Heilshorn, S. C., Myung, D. 2023

    Abstract

    Bioengineered corneal tissue is a promising therapeutic modality for the treatment of corneal blindness as a substitute for cadaveric graft tissue. In this study, we fabricated a collagen gel using ultraviolet-A (UV-A) light and riboflavin as a photosensitizer (PhotoCol-RB) as an in situ-forming matrix to fill corneal wounds and create a cohesive interface between the crosslinked gel and adjacent collagen. The PhotoCol-RB gels supported corneal epithelialization and exhibited higher transparency compared to physically crosslinked collagen. We showed that different riboflavin concentrations yielded gels with different mechanical and biological properties. In vitro experiments using human corneal epithelial cells (hCECs) showed that hCECs are able to proliferate on the gel and express corneal cell markers such as cytokeratin 12 (CK12) and tight junctions (ZO-1). Using an ex vivo burst assay, we also showed that the PhotoCol-RB gels are able to seal corneal perforations. Ex vivo organ culture of the gels filling lamellar keratectomy wounds showed that the epithelium that regenerated over the PhotoCol-RB gels formed a multilayer compared to just a double layer for those that grew over physically cross-linked collagen. These gels can be formed either in situ directly on the wound site to conform to the geometry of a defect, or can be preformed and then applied to the corneal wound. Our results indicate that PhotoCol-RB gels merit further investigation as a way to stabilize and repair deep and perforating corneal wounds.

    View details for DOI 10.1021/acsabm.3c00015

    View details for PubMedID 37126648

  • In Situ-Forming Collagen-Hyaluronate Semi-Interpenetrating Network Hydrogel Enhances Corneal Defect Repair. Translational vision science & technology Chen, F., Mundy, D. C., Le, P., Seo, Y. A., Logan, C. M., Fernandes-Cunha, G. M., Basco, C. A., Myung, D. 2022; 11 (10): 22

    Abstract

    Purpose: Millions worldwide suffer vision impairment or blindness from corneal injury, and there remains an urgent need for a more effective and accessible way to treat corneal defects. We have designed and characterized an in situ-forming semi-interpenetrating polymer network (SIPN) hydrogel using biomaterials widely used in ophthalmology and medicine.Methods: The SIPN was formed by cross-linking collagen type I with bifunctional polyethylene glycol using N-hydroxysuccinimide ester chemistry in the presence of linear hyaluronic acid (HA). Gelation time and the mechanical, optical, swelling, and degradation properties of the SIPN were assessed. Cytocompatibility with human corneal epithelial cells and corneal stromal stem cells (CSSCs) was determined in vitro, as was the spatial distribution of encapsulated CSSCs within the SIPN. In vivo wound healing was evaluated by multimodal imaging in an anterior lamellar keratectomy injury model in rabbits, followed by immunohistochemical analysis of treated and untreated tissues.Results: The collagen-hyaluronate SIPN formed in situ without an external energy source and demonstrated mechanical and optical properties similar to the cornea. It was biocompatible with human corneal cells, enhancing CSSC viability when compared with collagen gel controls and preventing encapsulated CSSC sedimentation. In vivo application of the SIPN significantly reduced stromal defect size compared with controls after 7 days and promoted multilayered epithelial regeneration.Conclusions: This in situ-forming SIPN hydrogel may be a promising alternative to keratoplasty and represents a step toward expanding treatment options for patients suffering from corneal injury.Translational Relevance: We detail the synthesis and initial characterization of an SIPN hydrogel as a potential alternative to lamellar keratoplasty and a tunable platform for further development in corneal tissue engineering and therapeutic cell delivery.

    View details for DOI 10.1167/tvst.11.10.22

    View details for PubMedID 36239965

  • Effect of Recombinant Human Lubricin on Model Tear Film Stability. Translational vision science & technology Cui, K. W., Xia, V. X., Cirera-Salinas, D., Myung, D., Fuller, G. G. 2022; 11 (9): 9

    Abstract

    Purpose: To investigate and quantify the effect of recombinant human lubricin (rh-lubricin) on model tear film stability.Methods: A custom-built, interferometry-based instrument called the Interfacial Dewetting and Drainage Optical Platform was used to create and record the spatiotemporal evolution of model acellular tear films. Image segmentation and analysis was performed in MATLAB to extract the most essential features from the wet area fraction versus time curve, namely the evaporative break-up time and the final wet area fraction (A10). These two parameters indicate the tear film stability in the presence of rh-lubricin in its unstressed and stressed forms.Results: Our parameters successfully captured the trend of increasing tear film stability with increasing rh-lubricin concentration, and captured differences in rh-lubricin efficacy after various industrially relevant stresses. Specifically, aggregation and fragmentation caused by a 4-week, high temperature stress condition negatively impacted rh-lubricin's ability to maintain model tear film stability. Adsorbed rh-lubricin alone was not sufficient to resist break-up and maintain full area coverage of the model tear film surface.Conclusions: Our results demonstrate that fragmentation and aggregation can negatively impact rh-lubricin's ability to maintain a stable tear film. In addition, the ability of rh-lubricin to maintain wetted area coverage is due to both freely dispersed and adsorbed rh-lubricin.Translational Relevance: Our platform and analysis method provide a facile, intuitive, and clinically relevant means to quantify the effect of ophthalmic drugs and formulations intended for improving tear film stability, as well as capture differences between variants related to drug stability and efficacy.

    View details for DOI 10.1167/tvst.11.9.9

    View details for PubMedID 36112103

  • Tear Film Stability as a Function of Tunable Mucin Concentration Attached to Supported Lipid Bilayers JOURNAL OF PHYSICAL CHEMISTRY B Cui, K. W., Myung, D. J., Fuller, G. G. 2022
  • In Situ-forming Collagen Hydrogels Crosslinked by Multifunctional Polyethylene Glycol as a Matrix Therapy for Corneal Defects: 2-Month Follow-Up In Vivo. Cornea Logan, C. M., Fernandes-Cunha, G. M., Chen, F., Le, P., Mundy, D., Na, K. S., Myung, D. 2022

    Abstract

    PURPOSE: We recently showed that in situ-forming collagen gels crosslinked through multifunctional polyethylene glycol (PEG) supported corneal epithelialization 7 days after treatment of lamellar keratectomy wounds. In this study, we aimed to evaluate the longer-term regenerative effects of this gel in animals.METHOD: Corneal wound healing was assessed 60 days after lamellar keratectomy and gel treatment using slitlamp examination, optical coherence tomography (OCT), pachymetry, corneal topography, an ocular response analyzer, and tonometry. The corneas were evaluated for the presence of beta-tubulin, cytokeratin 3, zonula occludens-1, and alpha smooth muscle actin (SMA) markers. Gene expression of aldehyde dehydrogenase 3A1 (ALDH3A1), cluster of differentiation 31, CD163, alpha-SMA, hepatocyte growth factor, and fibroblast growth factor 2 (FGF-2) and protein expression of CD44 and collagen VI were evaluated.RESULTS: Intraocular pressure, corneal thickness, and hysteresis for the corneas treated with collagen-PEG gels did not significantly change compared with the saline group. However, placido disk topography revealed greater regularity of the central cornea in the gel-treated group compared to the saline group. The gel-treated group exhibited a lower degree of epithelial hyperplasia than the saline group. Immunohistochemical and gene expression analysis showed that the gel-treated corneas exhibited lower alpha-SMA expression compared with the saline group. CD163 and CD44 were found to be elevated in the saline-treated group compared with normal corneas.CONCLUSIONS: The in situ-forming collagen-PEG gel promoted epithelialization that improved central corneal topography, epithelial layer morphology, and reduced expression of fibrotic and inflammatory biomarkers after 60 days compared to the saline group.

    View details for DOI 10.1097/ICO.0000000000003104

    View details for PubMedID 35965399

  • Predicting Systemic Health Features from Retinal Fundus Images Using Transfer-Learning-Based Artificial Intelligence Models. Diagnostics (Basel, Switzerland) Khan, N. C., Perera, C., Dow, E. R., Chen, K. M., Mahajan, V. B., Mruthyunjaya, P., Do, D. V., Leng, T., Myung, D. 2022; 12 (7)

    Abstract

    While color fundus photos are used in routine clinical practice to diagnose ophthalmic conditions, evidence suggests that ocular imaging contains valuable information regarding the systemic health features of patients. These features can be identified through computer vision techniques including deep learning (DL) artificial intelligence (AI) models. We aim to construct a DL model that can predict systemic features from fundus images and to determine the optimal method of model construction for this task. Data were collected from a cohort of patients undergoing diabetic retinopathy screening between March 2020 and March 2021. Two models were created for each of 12 systemic health features based on the DenseNet201 architecture: one utilizing transfer learning with images from ImageNet and another from 35,126 fundus images. Here, 1277 fundus images were used to train the AI models. Area under the receiver operating characteristics curve (AUROC) scores were used to compare the model performance. Models utilizing the ImageNet transfer learning data were superior to those using retinal images for transfer learning (mean AUROC 0.78 vs. 0.65, p-value < 0.001). Models using ImageNet pretraining were able to predict systemic features including ethnicity (AUROC 0.93), age > 70 (AUROC 0.90), gender (AUROC 0.85), ACE inhibitor (AUROC 0.82), and ARB medication use (AUROC 0.78). We conclude that fundus images contain valuable information about the systemic characteristics of a patient. To optimize DL model performance, we recommend that even domain specific models consider using transfer learning from more generalized image sets to improve accuracy.

    View details for DOI 10.3390/diagnostics12071714

    View details for PubMedID 35885619

  • Smart contact lens containing hyaluronate-rose bengal conjugate for biophotonic myopia vision correction. Biomaterials science Mun, J., Kim, T. Y., Myung, D., Hahn, S. K. 2022

    Abstract

    As the collagen layer weakens with increasing age or certain diseases such as keratoconus and myopia, the mechanical property of the collagen layer decreases with corneal deformation. To circumvent these problems, the corneal collagen has been crosslinked with the photosensitizer riboflavin under UV light after de-epithelialization. However, this treatment with riboflavin and UV light can cause notable damage to the eye. Here, the biocompatible rose bengal (RB) dye was conjugated to hyaluronic acid (HA) to enhance the corneal permeability, which can be activated by safe green light with a wavelength of 530 nm. Two-photon microscopy revealed the deep tissue penetration of the HA-RB conjugate in comparison with RB. Collagen fibrillogenesis, ex vivo tensile test, and ex vivo histological analysis confirmed the effective collagen crosslinking by HA-RB conjugate and the light irradiation. Furthermore, we developed a smart contact lens for on-demand HA-RB conjugate delivery from the reservoir embedded in the contact lens. Taken together, we could envision the feasibility of a smart contact lens for biophotonic myopia vision correction.

    View details for DOI 10.1039/d2bm00584k

    View details for PubMedID 35815427

  • Hyaluronic acid hydrogels crosslinked via blue light-induced thiol-ene reaction for the treatment of rat corneal alkali burn. Regenerative therapy Park, S. K., Ha, M., Kim, E. J., Seo, Y. A., Lee, H. J., Myung, D., Kim, H., Na, K. 2022; 20: 51-60

    Abstract

    To assess corneal inflammation from alkali chemical burns, we examined the therapeutic effects of in situ-forming hyaluronic acid (HA) hydrogels crosslinked via blue light-induced thiol-ene reaction on a rat corneal alkali burn model. Animals were divided into three groups (n=7 rats per group): untreated, treated with 0.1% HA eye drops, and treated with crosslinked HA hydrogels. Crosslinking of HA hydrogel followed by the administration of HA eye drops and crosslinked HA hydrogels were carried out once a day from days 0-4. Corneal re-epithelialization, opacity, neovascularization, thickness, and histology were evaluated to compare the therapeutic effects of the three groups. Further investigation was conducted on the transparency of HA hydrogels to acquire the practical capabilities of hydrogel as a reservoir for drug delivery. Compared to untreated animals, animals treated with crosslinked HA hydrogels exhibited greater corneal re-epithelialization on days 1, 2, 4, and 7 post-injury (p=0.004, p=0.007, p=0.008, and p=0.034, respectively) and the least corneal neovascularization (p=0.008). Histological analysis revealed lower infiltration of stromal inflammatory cells and compact collagen structure in crosslinked HA hydrogel-treated animals than in untreated animals. These findings corresponded with immunohistochemical analyses indicating that the expression of inflammatory markers such as alpha-SMA, MMP9, and IL1-beta was lower in animals treated with crosslinked HA hydrogels than untreated animals and animals treated only with 0.1% HA eye drops. With beneficial pharmacological effects such as re-epithelization and anti-inflammation, in situ-forming hyaluronic acid (HA) hydrogels may be a promising approach to effective drug delivery in cases of corneal burn injuries.

    View details for DOI 10.1016/j.reth.2022.03.005

    View details for PubMedID 35402662

  • Effect of hepatocyte growth factor-loaded collagen-PEG gels on corneal wound healing Naranjo, A., Cunha, G., Myung, D. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022
  • Inorganic polyphosphate-collagen complexes improve corneal epithelial cell function under glucose starvation and enhance corneal wound healing Rogers, G., Myung, D. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022
  • Epidermal growth factor-loaded collagen gels to enhance corneal wound healing: Effect of matrix crosslinking chemistry Seo, Y., Rogers, G., Myung, D. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022
  • A Pilot Study on Novel Ptotic Eye Dataset: Automated Prediction of Horizontal Corneal Diameter on Digital Photos of Taiwanese Ptotic Patients by Convolutional Neural Networks (CNNs) Hung, J., Chen, K., Chandrashan, P., Myung, D., Kossler, A., Fuh, C., Liao, S., Hsu, C. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022