Abstract
Abstract: :
Purpose: The photopic negative response (PhNR) is reported that it originates from ganglion cells or their axons (Viswanathan et al. 1999). We attempted to examine how the PhNR is affected in eyes with central retinal artery occlusion (CRAO) to evaluate functional loss of ganglion cells in this disease. Methods:Subjects comprised of 6 men and 1 woman with unilateral CRAO, ranging in age from 49 to 76 with a mean of 58.9 years. The rod and maximum ERGs were obtained with white stimuli of 0.48 and 3.3 log cd/m2, respectively, with 3 msec duration. Cone ERGs and 30 Hz flicker ERGs were recorded by stimuli of 3.0 log cd/m2 with 3 msec duration and 2.0 log cd/m2 with 33.3 msec duration, respectively, under a white background of 40 cd/m2. The PhNR amplitude was measured from baseline to a negative trough between the cone b– and i–waves. Each ERG amplitude measured in affected eyes was expressed as a percentage of the amplitude of corresponding wave in unaffected eyes. Results: The PhNR amplitude was reduced to 12.3 ± 11.7 % (mean ± standard deviation) of that observed in the unaffected eyes while the cone b–wave was attenuated to only 73.4 ± 30.4 %. This reduction of the PhNR amplitude was significantly greater than other waves including rod b–waves, maximum a– and b–waves, cone a– and b–waves, and 30 Hz flicker ERG (P < .001 for the maximum a–waves, cone a–waves and 30 Hz flicker ERG; P = .004 for the rod b–waves, maximum b–waves and cone b–waves, Student’s t–test). Conclusions: The PhNR was severely affected in eyes with CRAO despite relative preservation of the cone b–wave.This finding implicates massive loss of ganglion cells and their axons in CRAO.
Keywords: electroretinography: clinical • vascular occlusion/vascular occlusive disease • retina