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S. Kaidzu, T. Okuno, M. Tanito, A. Ohira; Action Spectrum of Retinal Light Damage in Albino Rats. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3616.
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Rodent models of retinal damage induced by visible light are widely used as experimental models of retinal degeneration. However, the action spectrum of retinal light damage in rodents is not fully understood. We tested the stimulation-response relationship between wavelength of light and the resultant damage in rat retinas.
Under deep anesthesia, left eyes of Sprague-Dawley albino rats (5-week-old, n=5-6 rats for each wavelength) were exposed to seven narrow-band lights (420, 440, 460, 500, 540, 580 and 620 nm) with16-29 nm in bandwidth, using a xenon lamp source with bandpass filters (Asahi Spectra Co., Ltd., Tokyo, Japan). The right eyes, left unexposed to light, served as controls. Duration of exposure was set so that retinal radiant exposure was 340 or 680 J/cm2, determined by measuring corneal radiant exposure and multiplying it by the cornea and lens transmittance of rat. Seven days after exposure, flash electroretinograms (ERGs) were recorded and both eyes were enucleated. 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.
Compared to unexposed eyes, significant reductions in a- and b-wave ERG amplitudes were observed in eyes exposed to light of 500 nm or shorter wavelengths. Decreased ERG amplitudes and ONL thicknesses were most prominent in eyes exposed to 420 nm light at both radiant exposures. Compared to unexposed eyes, a- and b-waves were not significantly different in eyes exposed to 540 nm or longer wavelength lights.
In rats, shorter wavelengths of light cause more severe retinal damage than longer wavelengths. Rodent models of acute light damage could be useful to test the "blue-light hazard" effects reported in humans and monkeys.
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