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Light-induced variations of retinal sensitivity in rats
I Ranchon1, J M Gorrand, J Cluzel
1Laboratory of Biophysics, School of Pharmacy, University of Auvergne, Clermont-Ferrand, France. isabelle.ranchon@u-clermont1.fr
Purpose:
ERG responses were measured as a function of Ganzfeld luminance to evaluate functional damage induced by light on rat retinas.
Methods:
Wistar rats were exposed to a fluorescent light of 1700 lux for 12 h, 24 h, 48 h and 72 h. We recorded ERGs before and one night after exposure, then 3, 8, 15, 22 and 29 days later. The b- and PIII-wave amplitudes were plotted against luminance for each group at each recovery time.
Results:
The retinal damage induced by a pupillary illuminance of 1700 lux ranged from low to severe as exposure duration increased from 12 h to 72 h, respectively. We observed an effect immediately after light exposure but no improvement during the recovery period. The b-wave amplitude was reduced by 40, 60, 80 and 90 percent after 12, 24, 48 and 72 h of light exposure, respectively; the PIII-wave amplitude was reduced by 30, 40, 70 and 90 percent after these respective exposures. The Ganzfeld luminance eliciting a 50 microV b-wave amplitude increased significantly with exposure duration, but the luminance eliciting the maximal b-wave amplitude was not dependent on this duration. Hence we suggest that the ERG decrease is due to a reduction in photoreceptor number.
Conclusions:
We present a full analysis of the electrophysiological parameters recorded from light-exposed or non-exposed rats. This model is a useful tool to study in vivo retinal degeneration.