Objective assessment of visual acuity using visually evoked potentials in response to fast sequences of pattern stimuli of different spatial frequency - a study to determine the clinical relevance

Background In patients where reliable subjective assessment of visual acuit y is impossible, further diagnostics should be enhanced by an objective met hod. Patients and methods A group of 34 patients was examined by objective asses sment of visual acuity using visual evoked potentials (VEP) as described by Hajek and Zrenner in 1988. The presentation of five checkerboards with dif ferent spatial frequency in repetitive sequences on a TV-monitor elicits a series of transient visual evoked potentials. Shape and amplitude of each w avelet depends on check size and directly reflect a spatial tuning function with a low- and high-frequency cut-off. This amplitude is described by a p olynomial fit (2nd order). The function's intersection with the x-axis at h igher spatial frequencies leads to an estimation of the visual acuity. Result This result is compared to the subjectively determined visual acuity . In the majority of the presented cases the suspected malingering was conf irmed. Conclusion Patients with suspected malingering represent the primary indica tion of the described method.