An amplitude ratio of pattern visually evoked cortical potentials.

PURPOSE: We evaluated the amplitude of steady state pattern visually evoked cortical potentials (St PVECP) by comparing the amplitude ratio to transient PVECP (Tr PVECP) with the latency of Tr PVECP in macular, optic nerve, and chiasmal lesions.

METHODS

PVECPs were obtained by pattern reversal stimulation of both 3 times and 12 times per second from normal subjects and patients. The peak latency of the P100 component of Tr PVECP and the amplitude ratio (St PVECP/ Tr PVECP) were studied.

RESULTS

Ratio abnormalities were specifically found in patients with optic and chiasmal lesions who had normal Tr PVECP latency, but not in those with macular lesions. The ratio increased with visual improvement in optic nerve disease and chiasmal lesions.

CONCLUSION

The amplitude ratio was useful in detecting and monitoring optic nerve and chiasmal lesions, and in differentiating optic nerve and chiasmal lesions from macular lesions.