A clinical grading system for retinal inflammation in the chronic model of experimental autoimmune uveoretinitis using digital fundus images

Experimental autoimmune uveoretinitis (EAU), a widely used animal model of human posterior/pan-uveitis, is extremely valuable in allowing understanding of the pathogenesis of uveitis as well as in developing new treatments. Depending on the animal strain and immunization protocol used, the clinical course of EAU can be acute, severe and involving the anterior and posterior part of the eye, or chronic, mild and involving only the posterior part of the eye. Clinical signs of EAU can be examined by bio-microscopy. Using appropriate criteria EAU can be quantitatively evaluated clinically in living animals. However, correlation of research within different laboratories is difficult since clinical grading systems are subjective and susceptible to considerable variability. In this study, we have developed a recordable, image-based clinical grading system for the chronic models of EAU. Fundus images were taken from EAU mice using an endoscopic imaging system. Fundus changes were classified as (1) inflammatory changes (including optic disc inflammation, vasculitis and retinal tissue inflammation) and (2) retinal structural damage. Each element was scored separately based on the severity of the lesions, and the average score of the three inflammatory elements was used as the overall EAU clinical inflammation grade of the eye. The validity and reproducibility of the grading system was tested using a set of images scored independently in a masked manner by 5 individuals. The grading system proved robust, easy to use and reliable. We offer this image-based EAU clinical grading system as a useful quantitative evaluation method for clinical grading of the severity of inflammation in the chronic EAU model, in which the inflammation can be mild and mainly involves posterior part of the eye.