Changes of Visual Evoked Potentials with Varying Check Sizes and Stimulus Field Sizes

J Korean Assoc EMG Electrodiagn Med 1999;1(1):66-71.
Published online January 1, 1999.

Abstract

Objective : The purpose of study is to determine the optimal check sizes and stimulus field sizes to obtain constant latency and large amplitude of visual evoked potentials. Method : P100 latencies and N75-P100 amplitudes were evaluated in 21 healthy subjects. Four check sizes(visual angle of 12', 25', 50' and 100') and five stimulus field sizes(visual angle of 3x2.4º, 6x4.8º, 9x7.2º, 12x9.6º and 15x12º)were used as stimulus parameter. Results : 1. Maximum N75-P100 amplitudes were obtained with 25' check size in small stimulus field size(3x2.4º and 6x4.8º) and 50' check size in large stimulus field sizes(9x7.2º, 12x9.6º and 15x12º) 2. p100 latency was similar for 25', 50' and 100' check sizes, but was longer for 12' check size (p<0.05). 3. Woth an increase in the stimulus field size from 3x2.4º to 12x9.6º, the N75-P100 amplitude increased steadily (p<0.05). 4. P100 latency was similar for 9x7.2º, 12x9.6º and 15x12º stimulus field sizes, but was progressively longer for 3x2.4º and 6x4.8º stimulus field sizes (p<0.05). Conclusion : when used 25' or 50' check sizes and stimulus field sizes above 9x7.2º, we obtained constant P100 latency and large N75-P100 amplitude of visual evoked potentials.

Key Words: Visual evoked potential, Check size, Stimulus field size