Pattern visual evoked potential in the diagnosis of functional visual loss

Objective: To study the pattern visual evoked potential (P-VEP) in the diag nosis of functional visual loss. Study Design: Retrospective study of observational case series. Participants: Seventy-two subjects whose best corrected visual acuity (VA) was 20/50 or worse, with or without visual field defect, and whose visual a bnormalities could not be explained by the findings of ophthalmologic and n eurologic examination were included in this study. Main Outcome Measures: To compare the P-VEP estimated acuity to the initial subjective VA and to the best-performed VA. Results: Seventy-two subjects with functional visual loss had normal P-VEPs . The initial subjective VA was 20/50 in 9 subjects and less than or equal to 20/200 in 42 subjects. After clinical examination and reassurance, the b est-performed VA was greater than or equal to 20/50 in 53 subjects and less than or equal to 20/200 in 8 subjects. The discrepancy between the P-VEP e stimated 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. Th ese six subjects were three women with loss of vision of unknown origin and three men with injury-related visual loss. Conclusions: P-VEP has the advantage of objectively predicting VA and is a useful test in the diagnosis of functional visual loss. Ophthalmology 2001; 108:76-81 (C) 2001 by the American Academy of Ophthalmology.