Ultrastructural changes in rat eyes with experimental Vogt-Koyanagi-Harada disease

Purpose: To determine whether the ultrastructural changes in the eyes of an animal model of Vogt-Koyanagi-Harada (VKH) disease are similar to those in human eyes with VKH disease. Methods: Pigmented rats derived by crossing brown Norway and Lewis rats were immunized with tyrosinase-family proteins, and the eyes were enucleated after different postinoculation times. The eyes were fixed in glutaraldehyde or formaldehyde and prepared for light or electron microscopy (EM). Results: EM showed that thickening of the choroid resulted from the invasion of many lymphocytes and epithelioid-like cells. The melanocytes were surrounded by lymphocytes and lost their normal spindle shape. Neutrophils and eosinophils were also present in the choroid. These findings are very similar to the changes reported in eyes from patients with VKH disease or sympathetic ophthalmia. Conclusions: The similarity of the ultrastructural changes in this model to those in human VKH disease indicate that this animal model can serve as a histopathological model of human VKH disease.