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G Ben-Shlomo, S Bakalash, GN Lambrou, CL Percicot, WW Dawson, M Schwartz, R Ofri; Functional Deficits in a Rat Model of Chronically Elevated Intraocular Pressure . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2142.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To use the pattern electroretinogram (PERG) to detect retinal function deficits in a rat model of chronically elevated intraocular pressure (IOP). Methods: Argon laser photocoagulation of the episcleral veins and limbal plexus was used to induce unilateral IOP elevation in 6 Lewis rats. Scotopic PERG responses were recorded prior to lasering and 3 weeks later. Stimulus was a series of 5 shifting (6 Hz) checkerboard patterns of decreasing spatial frequency (32-2 cycles per degree, cpd), projected ophthalmoscopically on the animals' fundus. Results: Mean (± standard deviation) IOP was 17.9 ± 4.2 mm Hg in normal eyes, and 30.8 ± 6.0 mm Hg in lasered eyes. Responses from both normotensive and hypertensive eyes showed a typical spatial frequency dependence. N1P1 amplitude increased with the size of the stimulus, peaking in response to a 4 cpd pattern. In eyes with elevated IOP, signal amplitude was reduced in response to all patterns, with significantly (P < 0.05) lower signals recorded in response to wide stimuli. Mean responses to 4 cpd patterns were 12.26 ± 3.59 uV in normal eyes, compared to 6.95 ± 0.76 uV in eyes with elevated IOP. Mean responses to 2 cpd patterns were 7.91 ± 1.97 uV in normal eyes, compared to 5.52 ± 1.61 uV in eyes with elevated IOP. Signal latency was similarly decreased in these eyes. Conclusion: The PERG of rat eyes with chronically elevated IOP shows an amplitude reduction of 30-43% in response to wide gratings. These deficits provide an indication of functional damage in the magnocellular pathways, which have been shown to be preferentially damaged in non-human primate models of glaucoma. The evidence for functional deficits, combined with tonometry and documentation of ganglion cell loss, confirms the validity and importance of this animal model in glaucoma research.
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