Manifestation of oblique effect on transient pattern reversal visual evoked potential P100 amplitude and latency in large random sample of healthy individuals and subjects with primary open angle glaucoma

Abstract

Purpose The objective of the present study was to investigate and compare manifestation of the oblique effect on transient pattern reversal VEP P100 amplitude and latency between a large random sample of healthy individuals and subjects with primary open angle glaucoma (POAG). Methods A random sample of 500 Kaunas (Lithuania) inhabitants aged 45–72 years, participating in HAPIEE (Health, Alcohol, Psychosocial factors In Eastern Europe) cohort study underwent ophthalmologic examination and 63 adults matched the inclusion—exclusion criteria. The POAG group consisted of patients, treated in Lithuanian Health Science University Hospital Eye clinic. The latter group was divided into those whose Humphrey automated perimetry (24-2) MD was -6.0 dB or better (POAG_1) and those whose MD was -6.01 dB or worse (POAG_2). Stimuli were sinusoidal gratings of 9 cpd spatial frequency and 100 % contrast generated by Visual Stimulus Generator 2/3 (Cambridge Research Systems) and displayed on a IBM p76 CRT monitor at 80 Hz rate. Stimulation was synchronized with recording equipment (Retiport, Roland Consult) via a TTL connector board. Stimuli were presented at four orientations (0, 45, 90 and 135 degrees). The mean luminance of the monitor was 50 cd/m2. The stimulus area on display was circular and subtended 10 degrees in diameter at a viewing distance of 1 meter. The stimulus pattern alternated at the 1 Hz rate (2 reversals per second). The signal was filtered within 0.5–50 Hz bandwidth. Analysis time was 300 ms. Averages of at least 75 repetitions were obtained. The amplitude and latency of major... [...].