Long term light-induced retinal degeneration in the miniature pig.

In developing a model of slow light-induced retinal degeneration, ten miniature pigs were submitted to constant lighting for a period ranging from one to three months. Post-lighting survival time ranged from zero to two months. Control and illuminated animals were examined for pupillary reflex, underwent fundus examination and an electroretinogram. After euthanasia, retinas were processed for histology with measure of outer nuclear layer thickness. All animals illuminated one or more months had pupillar reflex alteration. Mean outer nuclear thickness was 24.12 microns in the control and ranged from 18.36 to 21.45 microns in illuminated animals (mean reduction 20%). Despite the pigmentation of miniature pigs, consistent results were obtained in the absence of pharmacologic pupil dilation.