Abstract
Purpose: :
Ultraviolet light (UV) is hazardous compared with visible light to the eye. However, the damaging effect(s) of UV on the retina in in vivo has not been fully examined. In this study, we tested the stimulation-response relationship between the UV exposure dose and the resultant damage in rat retinas at different UV wavelengths.
Methods: :
Under deep anesthesia, the left eyes of 5-week-old Sprague-Dawley albino rats (n=6 for each condition) were exposed to five narrow-band lights with 10 nm in bandwidth at wavelengths of 330, 340, 360, 380 and 400 nm, using a xenon lamp source with bandpass filters (Asahi Spectra Co., Ltd., Tokyo, Japan). The right eyes, left unexposed to light, served as controls. For each wavelength, rats were exposed to 5 or 6 different doses (retinal radiant exposure) ranging from 0.6 to 170 J/cm2 to obtain stimulation-response relationship. The retinal radiant exposure was determined by multiplying the measured corneal radiant exposure by the combined transmittance of the rat lens and cornea. Seven days after the exposure, flash electroretinograms (ERGs) were recorded and the radiant exposure that causes 50 % reduction in ERG b-wave amplitudes (ED50) was calculated for each wavelength of light. Both eyes were enucleated and retinal sections containing the whole retina including the optic disc were stained with hematoxylin-eosin (H & E) and outer nuclear layer (ONL) thickness was measured.
Results: :
Compared to unexposed eyes, significant reductions in a- and b-wave ERG amplitudes and in ONL thickness were observed for all wavelengths of light tested. ED50 of 330, 340, 360, 380, and 400 nm were calculated to be 4.14, 5.04, 7.06, 17.10 and 57.5 J/cm2 in a-wave and 2.89, 4.10, 5.87, 13.3 and 43.2 J/cm2 in b-wave respectively.
Conclusions: :
Stimulation-response relationship curve in UV-induced retinal damage were obtained in rats. As expected, retinal damage induced by UV depends on wavelength and radiant exposure. Compared to longer wavelengths, shorter wavelengths cause more severe retinal damage.
Keywords: radiation damage: light/UV • retina • retinal degenerations: cell biology