Investigation of multifocal visual evoked potential in anisometropic and esotropic amblyopes

To investigate the variation of visual evoked potential (VEP) function at different eccentricities of the visual field in esotropic amblyopes and anisometropic amblyopes.

Data from 5 esotropic amblyopic eyes, 6 anisometropic amblyopic eyes, and 45 control eyes were analyzed. A VERIS system was used to generate a stimulus matrix containing 61 hexagons on a computer monitor. Each hexagon of the display contained a number of small black and white hexagonal patches that reversed in polarity during stimulation according to a pseudorandom binary m-sequence. The VERIS system extracted the local responses by cross-correlating the input and output signals. The latencies and amplitudes of the responses from the central 8.6 degrees of arc in the visual field were analyzed.

In esotropic amblyopia, the multifocal VEP latency is prolonged, and the amplitude is reduced in the central region of the visual field. The mean amplitude is significantly smaller, and the mean latency is significantly longer in the temporal visual field than in the nasal visual field. In anisometropic amblyopia, latencies are markedly prolonged, and the amplitudes of multifocal VEP are attenuated in the central region of the visual field, and these effects are lessened in the periphery.

The results are in agreement with psychophysical studies reporting a greater foveal deficit in amblyopia and a greater visual loss in the temporal field than in the nasal field in esotropic amblyopia.