Measurement of Retino-Cortical Conduction Time using Pattern Reversal Stimulation for Detection of Subclinical Visual Dysfunction.

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1. Transient pattern reversal visual evoked potentials in 167 healthy subjects.The subjects consisted of 71 males and 96 females. Their mean age was 45.7 +19.1. A three kinds of check size was used ; 15, 30 & 60 minutes. Measuring parameters consisted of VEP latencies (P50, N75, P100, N145) and VEP amplitudes (N75, P100, N145). Pattern VEP to 15 min checks showed significantly prolonged and larger responses, compared with VEP to 30 or 60 min checks. VEP latency and age showed curvilinear correlation. VEP amplitude and head circumference showed a negative linear correlation. Pattern VEP in males showed significantly prolonged and smaller responses, compared with VEP in females.2. Transient/Steady-state pattern reversal ERG/VEP in 114 healthy subjectsThe mean age of the 114 healthy subjects was 45 years. Two kinds of pattern reversal rates were used ; 0.8 Hz (transient) and 5 Hz (steady-state). Check sizes used were 15, 30 & 60 minutes. ERG was recorded using two gold-foil electrodes placed in lower eyelids. Transient ERG consisted of a(p), b(p) and c(p). Transient VEP consisted of P50, N75, P100 and N145. Steady-state ERG showed peaks of N1, P1, N2, P2, N3 & P3. Steady-state VEP showed peaks of NI, PI, NII, PII, NIII & PIII. Transient or steady-state ERG/VEP latencies showed a curvilinear correlation to age. Retino-cortical time and age showed a curvilinear correlation, too. Transient/steady-state ERG amplitudes decreased with increasing age. VEP amplitudes decreased with increasing head circumference.3. Pattern reversal ERG/VEP in multiple sclerosis, optic neuritis and HTLV-I associated myelopathy.There were three types of abnormalities ; (1) normal ERG and prolonged VEP, (2) reduced or absent ERG and prolonged VEP, (3) absent responses in both ERG & VEP.Our present study contributes to (1) understanding of normal physiological knowledge of visual system, and (2) effective and non-invasive detection of subclinical visual system disorders.