Separate mechanisms for retinal damage by ultraviolet-A and mid-visible light.

Retinal damage by light has two distinct action spectra, one peaking in the ultraviolet-A (UVA) and the other in the mid-visible wavelengths (green light). Here we show in a single animal species, the Long Evans rat, that UVA and green light can produce histologically dissimilar types of damage. UVA light in particular produces severe retinal damage at low irradiation levels. Furthermore, the mechanism of damage by UVA light is different from that of green light as determined by their relative rhodopsin bleaching efficacies. These results provide convincing evidence that different chromophores mediate damage by UVA and green light. By producing both classes of damage in a single species, a sound model is provided for further investigation into the different forms of photic retinopathy.