Electroretinographic abnormalities in a rat glaucoma model with chronic elevated intraocular pressure

The purpose of this study was to determine the ability of electroretinograp hic (ERG) measurements to document progression of the retinopathy in a rat glaucoma model. Thirty four rats with a chronic intraocular pressure (IOP) elevation induced in one eye by cautery of three episcleral/extra-orbital v eins were studied in four separate groups. ERGs were recorded sequentially in Group A rats (n = 12) at baseline, and after approximately 20, 40 and 60 days of high IOP, and in three additional groups of rats (n = 6 or 10 per group) after approximately 58, 30 and 175 days of high IOP, respectively. S cotopic ERG parameters recorded simultaneously from both eyes in Group A ra ts were: a- and b-wave amplitudes, implicit times, oscillatory potential am plitudes (OPs) determined at three different light-flash intensities, and t he light-adapted (photopic) ERG b-wave amplitude. In the other groups of ra ts, only scotopic ERG a-wave, b-wave and OP amplitudes were measured. In Group A rats that were followed sequentially, all the ERG parameters rec orded with attenuated stimuli showed significant time-dependent changes in glaucomatous eyes relative to their contralateral normal eyes, with OPs sho wing the earliest significant difference after only 3 weeks of high IOP. Wh en different groups of unilateral glaucomatous rats were compared beyond 8 weeks of elevated TOP only the OPs showed a continued decrease with time an d good discrimination between glaucoma and normal eyes. Over a 25 week peri od of high IOP the scotopic OPs measured with attenuated light stimuli decl ined at the rate of approximately 1.5 % per week and provided the best ERG measure to monitor progression of retinal pathophysiology in the vein-occlu sion rat glaaucoma model. (C) 2001 Academic Press.