Histological findings in the Wistar rat cornea following UVB irradiation.

The acute clinical effect of UVR on the eye is photokeratitis, which is an inflammatory state that might be regarded as the sunburn of the eye. In this study, we used a rat model to assess the histological injuries induced in the intact rat cornea following its exposure to UVB radiation. A total of 15 two-months-old female Wistar rats were purchased from the Animal Facility of "Iuliu Hatieganu" University of Medicine and Pharmacy, Cluj-Napoca, Romania. The rats were fed ad libitum and kept under standard conditions with a 12 hours light/dark cycle. The rats were randomly divided into five groups, including control group (no UVB exposure), group II (a single exposure to a dose of 45 mJ UVB/cm(2) for 47 seconds), group III (a single exposure to 90 mJ UVB/cm(2) for one minute and 57 seconds), group IV (a single exposure to 180 mJ UVB/cm(2) for three minutes and 57 seconds), and group V (a single exposure to 360 mJ UVB/cm(2)² for five minutes and 26 seconds). After 24 hours of recovery, the rats were sacrificed by cervical dislocation. The rat eyes were extracted, harvested and fixed in 10% buffered formalin. The eye samples were then processed through paraffin technique for further histological examination. We found that, following the UVB exposure, the cornea showed significant inflammatory responses (infiltration of polymorphonuclear leukocytes), hemorrhage and gross damages such as superficial and deep ulcerous keratitis and epithelial exfoliation. The severity of these findings was associated with the increase of UVB radiation intensity and exposure period.