Visual Acuity Test
The Visual Acuity Test is used to assess visual discrimination and acuity in rodent models of CNS disorders. In this test, mice swim in a water tank with a clear plastic barrier and two cue cards of variable black and white gratings. On one side of the barrier is the escape platform, indicated by the cue card with the finest grating (which remains constant over the course of the test). The “incorrect” quadrant on the other side of the barrier contains no platform, marked by a cue card bearing a larger grating that remains a constant width through training. The testing is performed daily until an 80% correct response rate is achieved. A correct response requires the animal to find and remain on the platform without ever entering the incorrect quadrant. Subjects are then overtrained to >80% accuracy before beginning the testing phase.
In testing, the “incorrect” grating used in training is replaced by ones of diminishing widths to test the animals’ ability to discriminate between the cues. All trials are recorded with an overhead camera and analyzed by computer software for velocity and distance moved. The percentage of correct responses is also graphed. This test is useful for phenotyping transgenic strains of mice and evaluating novel chemical entities for their effect on visual acuity.