Pattern visual evoked potential in the diagnosis of functional visual loss.

Abstract

To study the pattern visual evoked potential (P-VEP) in the diagnosis of functional visual loss. Retrospective study of observational case series. Seventy-two subjects whose best corrected visual acuity (VA) was 20/50 or worse, with or without visual field defect, and whose visual abnormalities could not be explained by the findings of ophthalmologic and neurologic examination were included in this study. To compare the P-VEP estimated acuity to the initial subjective VA and to the best-performed VA. Seventy-two subjects with functional visual loss had normal P-VEPs. The initial subjective VA was 20/50 in 9 subjects and < or =20/200 in 42 subjects. After clinical examination and reassurance, the best-performed VA was > or =20/50 in 53 subjects and < or =20/200 in 8 subjects. The discrepancy between the P-VEP estimated acuity and the best-performed VA was less than 3 lines of Snellen acuity in 63 of 72 (87.5%) subjects and more than 4 lines in 6 subjects. These six subjects were three women with loss of vision of unknown origin and three men with injury-related visual loss. P-VEP has the advantage of objectively predicting VA and is a useful test in the diagnosis of functional visual loss.