Establishment Of A Method For The Visual Acuity Test On Cynomolgus Monkey

Abstract

Purpose: : To evaluate the visual function brought by the channelrhodopsin-2 (ChR2) gene transfer, the visual acuity test program adapted to cynomolgus monkeys was developed. To establish the monocular blindness model caused by the photoreceptor degeneration, we also tried various methods using rabbits to induce unilateral photoreceptor degeneration.

Methods: : The landolt ring-based visual acuity test was programmed by the python programming language. The volumes of drinking water for monkeys were controlled during the periods training the visual acuity test. The visual acuity test was performed 3 sessions per week and one hundred fifty trials in a session were done for an hour. We determined their visual acuity by evaluating a percentage of correct answers and reaction time. To establish the one eye-limited photoreceptor degeneration model, we injected various chemicals into rabbit eyes and investigated the retinal degeneration by histology and electroretinograms.

Results: : Cynomolgus monkeys could learn to do the visual acuity test after a month training. As decreasing the diameter (from 15cm to 1.5 cm) of the landolt ring, the percentage of correct answers decreased and the reaction time was extended. Nitric oxide (NO) donor, sodium nitroprusside (SNP), was intravitreously injected into rabbit eyes to induce retinal degeneration. SNP (<100 nmol/eye) injection induced photoreceptor degeneration predominantly but not ganglion cells.

Conclusions: : Our developed landolt ring based visual acuity test is easy to learn for monkeys and us, and useful for evaluating the visual function. Our unilateral photoreceptor degeneration model can be utilized for primates.

Keywords: gene transfer/gene therapy • retinal degenerations: hereditary • electrophysiology: non-clinical