ABSTRACT
The human eye might be subjected to repeated exposure to ultraviolet radiation [UVR] either during a single day or over a longer period of time. It is known that the cortical epithelium strongly absorbs UVR. The aim of this study was to evaluate the protective role of corneal epithelium against the effect of UVB radiation on corneas of albino rabbits in comparison with that on de-epithelialized corneas. Sixteen adult female New Zealand albino rabbits [3-3.5 Kg] were divided into 4 groups, 4 rabbits each. Group I served as control. Group II served also as control, but their corneas underwent manual de-. In group III, corneas were exposed to UVB irradiation, peaked at 3l2nm as a single dose [3.12J/cm2] for 30 minutes. In group IV corneas underwent manual de-epithelialization. 5 minutes prior to UVB exposure. All animals were sacrificed after 48 hours, and the corneas were removed and processed for histological and transmission electron microscopic study. The histological results of group III revealed that the corneas had slight edema and the keratocytes in the outer stroma appeared to be affected. Ultrastructural evaluation of this group showed affected epithelial cells and the keratocytes revealed early apoptotic changes like chromatin condensation. Results of group IV showed that the stromal damage was deeper and more extensive. The keratocytes had been markedly affected in the entire thickness and there was thinning out of Descemet's membrane. Ultrastructurally, the keratocytes showed chromatin condensation, fragmentation and cell shrinkage. Disorganized collagen lamellae were also seen. It was concluded that the removal of the corneal epithelium makes the underlying ocular structures-more susceptible to damage by UVB in the 312nm range. Further studies are needed to investigate whether the corneal epithelium has protective properties against UVB at other wavelengths