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D Raz, I Perlman, CL Percicot, GN Lambrou, R Ofri; Evidence of Inner and Mid Retinal Functional Damage in an Animal Model of Glaucoma . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2141.
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Purpose:To study the contribution of different retinal circuits to the multifocal electroretinogram (mfERG) response of normal and glaucomatous monkey eyes. Methods:Five normotensive eyes and 5 eyes with experimentally induced glaucoma of Cynomolgus monkeys were used in this study. A baseline 7 minute mfERG recording was performed, and similar recordings were performed after consecutive intravitreal injections of drugs known to selectively block activity of retinal cells. A combination of g-amino-butyric acid (GABA) & glycine was administered to block inhibitory circuits of the inner retina, followed by application of L-2-amino-phosphonobutyric acid (APB) to block transmission from photoreceptors to ON-bipolar cells. Subtraction of signals was used in order to segregate the contribution of different retinal elements. Results:In the normal eyes the component removed by GABA & glycine resembled the 2nd order response (K2). However, in the glaucomatous eyes the large component removed by GABA & glycine differed remarkably from the negligible K2 responses. In the responses of the normal eyes the component removed by APB had a complex positive potential, whereas the responses of the glaucomatous eyes had a simple positive potential of shorter duration. Conclusion:The pharmacological decomposition of the signals suggests that in the normal eyes inhibitory circuits of the inner retina contribute to the mfERG response. The discrepancy between K2 and the component removed by GABA & glycine in the glaucomatous eyes indicates damage to the inner retina. Furthermore, the component removed by APB denotes functional changes in the ON-bipolar pathway in the glaucomatous eyes.
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