Comparative effect of UVA and UVB on cultured rabbit lens.

Effects on lens physiology of UVB and UVA used separately and sequentially were investigated using 4 week old rabbit lenses in organ culture. Narrowband UVB at 0.3 J/cm2 = joules/lens (1 h exposure) has little effect on sodium and calcium concentrations in the lens interior or transparency of lenses subsequently cultured for 20 h after a 1 h exposure. With an incident energy of 3 J/cm2 of broadband UVB (295-330 nm), lenses become opaque and slightly swollen with significant ion imbalances during culture over a 1 day period. In contrast, lenses exposed to approximately 6-24 J/cm2 of UVA (330-400 nm) remain transparent after 1 day of culture. Extended culture up to 4 days reveals no signs of opacification. Ion homeostasis and normal lens hydration are also maintained in UVA-irradiated lenses. The presence of 95% oxygen during UVA irradiation is also without effect. Broadband UVA irradiation is damaging, however, if lenses are first exposed to subthreshold doses of narrowband UVB (307 +/- 5 nm) irradiation, viz. 0.3 J/cm2. Thus, sequential UVB/UVA irradiation at subthreshold doses causes impaired active cation transport and accumulation of sodium and calcium accompanying lens opacification.