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S. Joly, V. Pernet, A. Dorfman, H. Moukhles, S. Chemtob, P. Lachapelle; Functional and Structural Consequences of Postnatal Exposure to a Bright Luminous Environment on the Retina of Newborn Rats . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1870.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate how the developing retina reacts to a postnatal exposure to a bright luminous environment (Light Induced Retinopathy: LIR) and compare with postnatal exposure to hyperoxia (Oxygen-Induced Retinopathy: OIR). Methods: Litters of newborn albino Sprague Dawley rats were exposed with their mothers to 16000 lux (12L:12D) from birth to postnatal day 3 (0-3), 6 (0-6), 9 (0-9), 12 (0-12) or 14 (0-14) and compared to control rats maintained at 100 lux. Scotopic (intensity: -6.3 to 0.6 log cd.m-2.sec; 12 hours dark adaptation) and photopic (intensity: 0.9 log cd.m-2.sec; background: 30 cd.m-2) ERGs were recorded at age 30 and 60 days. Eyes were then enucleated and the retinae prepared for histology (0.7µm sections, toluidine blue staining). Results: All mothers showed unrecordable ERGs both in photopic and scotopic conditions. In contrast, after maximum exposure (0-14 group), scotopic ERGs of newborn rats aged 30 days were not significantly different from normal while the photopic ERGs showed a significant (p<.05) 40% increase in amplitude. Similarly the exposed rats yielded an exaggerated light adaptation effect compared to normal control rats (75% enhancement compared to 32% in normals). Measurements obtained at 60 days of age showed a significant reduction in amplitude of scotopic ERG measurements in all light-exposed groups (maximal effect in 0-14 group; a-wave: 46%; b-wave: 32%; p<.05), while photopic responses returned to normal amplitudes. Histological analysis only revealed a marked reduction in the cell count of the Outer Nuclear Layer. Conclusions: Postnatal exposure of newborn rats to a bright luminous environment will cause a retinopathy and that despite eyelid closure. The retinopathy thus created is different from OIR in that : 1-the retina appears to be equally susceptible throughout development, 2- cone and rod ERGs appear to be differently impaired (transient enhancement of cone vs long term reduction of rod ERGs) unlike OIR where they are both reduced 3- LIR worsens over time (30 vs 60 days) while OIR does not. LIR thus offers another means to investigate the postnatal susceptibility of the retina to environmental stresses. Funded by CIHR, Reseau Vision.
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