Reduction in Retinal Function in Laser-Induced Chronic Ocular Hypertensive Model in Rats

Abstract

Abstract: : Purpose: Laser photocoagulation-induced increase in IOP has resulted in selective loss of ganglion cells (IOVS 42:2849-2855, 2001). The aim of this study was to examine the effect of elevated IOP on different functions of the retina. Methods. IOP was elevated by laser photocoagulation of episcleral and limbal veins and was measured every two weeks. Electrophysiological recordings were done at 10, 30 and 60 days post IOP elevation. Flash ERG (0.3 to 500 Hz) and 20 Hz flicker were recorded at different light intensity (-30 to 7.5 dB) using LKC ganzfeld stimulator. The oscillatory potential (OP) responses were extracted using analog by pass from the flash ERG. Results: Laser photocoagulation of the episcleral and limbal veins resulted in elevation of IOP by two fold. There was a decrease in the different retinal functions measured as early as ten days after the elevation of IOP. The reduction was more evident at lower light intensities (-10dB). The greatest decrease was seen in OP but there were decreases in flicker response amplitudes as well. Conclusions: The decrease in all the retinal functions suggests that the retina as a whole is negatively affected by the stress of elevated IOP. The extent of the decrease in OP suggests that ganglion cells are the most sensitive to the insult of elevated pressure.

Keywords: electroretinography: non-clinical • intraocular pressure • retina