LOCATION AND SEVERITY OF UVB IRRADIATION DAMAGE IN THE RAT LENS

We investigated the location and severity of lens opacities and epithe lial alterations following ultraviolet-B (UVB) irradiation in vivo, us ing Brown Norway rats. A group of 9 rats received 65 mJ/cm(2) UVB irra diation from overhead lamps every 6 days. Lens changes were documented and evaluated by an anterior eye segment analysis system. Lens epithe lial cells were examined postmortem in flat preparations. After 8 week s of the irradiation schedule (total dose: 0.6 J/cm(2)), an anterior p olar opacity was apparent; at 16 weeks, the opacities had progressed m ore deeply into the cortex. At postmortem examination, cells in the ce ntral region displayed disorganization, clumping, some pyknotic nuclei and mitosis. There were deeper opacities and cell damage was more sev ere above the central horizontal plane than below it. This present stu dy demonstrated that UVB damage differed in the superior and inferior parts divided by a horizontal plane through the lens anterior pole, wh en the UVB source was above and there was no reflection from below or laterally. The lens epithelial cells, and associated lens fibers, are the first target of UVB irradiation. (C) 1997 Japanese Ophthalmologica l Society.