SLOWLY PROGRESSIVE CHANGES OF THE RETINA AND RETINAL-PIGMENT EPITHELIUM IN BRIARD DOGS WITH HEREDITARY RETINAL DYSTROPHY - A MORPHOLOGICAL-STUDY

Seven eyes from 2 generations of Briard dogs (5 weeks - 7 years old) w ith congenital night blindness and (in the second generation) impairme nt of day vision to varying degrees, were examined by light and electr on microscopy. Specimens from 4 locations were studied: the central ar ea, the midperiphery of the tapetal area, the upper periphery and the lower periphery, Disorientation of rod outer segment disc membranes wa s seen in the 5-week-old dog. Large electron-lucent inclusions were fo und in the RPE at 3.5 months of age. These inclusions occurred most fr equently in the central and midperipheral-tapetal areas and seemed to increase in numbers and spread towards the periphery with increasing a ge. The content of these inclusions is not elucidated. Rod photorecept or degeneration was apparent from 7 months of age and was most promine nt in the peripheral areas. The cones were better preserved. The 7-yea r-old dog showed reduction of photoreceptors in the central and midper ipheral-tapetal areas and almost complete photoreceptor degeneration i n the periphery. This dog also showed severe changes of the inner reti na in the peripheral fundus. it appears that these Briard dogs suffer from a very slowly progressive retinal degeneration, in which the phot oreceptor degenerative changes do not correlate anatomically to the ch anges in the RPE cells. The disease seems to be different from the ret inopathy described in the English Briards. It is not clear yet whether the lipid type of retinopathy found in American Briards is identical to the present disease.