123-128. Ruchi-Ramji

The objective of the present study is to determine the occurrence of “W” morphology of P100 waveform in Pattern Reversal Visual Evoked Potential (PRVEP) recordings of a cohort of patients having Primary open angle glaucoma. This rural hospital based study was conducted in the Neurophysiology unit of the Department of Physiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram. The study comprised of pattern reversal visual evoked potential (PRVEP) recordings from 176 eyes of 88 patients of primary open angle glaucoma (POAG) having age ≥40 years. The recordings were compared with those of 180 eyes of 90 age matched controls. VEP recordings were performed with the stimulus configuration consisting of the transient pattern reversal method in which a black and white checker board was generated (full field) and displayed on VEP Monitor (colour 14”) by an electronic pattern regenerator inbuilt in an Evoked Potential Recorder (RMS EMG EP MARK II). All the recordings were investigated for the presence of “W” shaped complex (bifid pattern of P100) defined as having two peaks separated by a 10-50 msec interval. The appearance of peculiar “W” pattern obtained in our POAG patients was an aberrant response encountered in 19.31 % percent (34 eyes) of 176 open angle glaucomatous eyes. None of the previous studies have commented on the morphology of P100 waveform in POAG patients as far as the literature could be traced so it seems that ours is a preliminary attempt in this regard. We propose that it may carry the similar significance as a prolonged P100 latency since the latency magnitude of the bifid peaks were beyond the upper limit of normal latency of P100 potential. However, the validation of this proposition warrants further investigation on a larger sample of POAG population.