Retinochoroidal Changes In The Mice After Chronic Ultraviolet Irradiation.

Y.H. Mohamed. El-Minia University Hospital, El-Minia, Egypt.

Purpose: To study the retinochoroidal morphological changes of the mice after chronic ultraviolet-A irradiation by using transmission electron microscopy (TEM).

Methods: SKH-1 hairless mice were employed in this study. Mice were exposed to UV at 300 kJ/ m/ day for five days/ week. Eyes were enucleated and retinas were dissected and prepared for TEM after 4th and 8th months of exposure.

Results: After 4th month of UV-A exposure the retinochoroidal changes include: marked vesiculation of retinal pigment epithelium (RPE) and endothelial cells of choriocapillaries; deposition of pigment clumps in the RPE; appearance of many phagocytic cells containing large amounts oflipid droplets and debris between the photoreceptor outer segments (ROS), and irregular distribution of ROS. After 8th month of exposure the retinochoroidal changes include: atrophy of the RPE in the central retina and marked deposition of lipid droplets and pigment clumps in the peripheral parts; increase number of phagocytic cells between photoreceptor outer segments; sparce distribution of ROS and inner segments and decreased number of photoreceptor nuclei in comparison to control eyes; patchy atrophy of choriocapillaries , and thickening of the basement membrane of endothelial cells of the choriocapillaries with narrowing of its lumen.

Conclusions: Chronic exposure to UV-A produces sever retinochoroidal damage at low levels of irradiation.