Michael H Graf1, Jens Roesen. 1. Department of Ophthalmology, Strabismology, and Neuroophthalmology, University of Giessen, Friedrichstrasse 18, D-35385 Giessen, Germany. michael.h.graef@augen.med.uni-giessen.de
Abstract
OBJECTIVE: To describe a visual acuity test for use in identifying psychogenic visual impairment and malingering. METHODS: The test contained 32 white plates with a black Landolt C printed in the center. The sequence of the 4 alternative directions of the C was not predictable. After plate 21, 4 circles were interspersed among the remaining plates. The test is administered at a distance from which the subject is presumed to be able to recognize the optotypes. He or she is requested to identify the direction of the C within 2 seconds, and the responses are noted. Two elements were evaluated: (1) The number of correct answers was compared with the corresponding value of the distribution function of the binomial formula that represents the probability of reaching this rate of correct answers by pure chance. (2) The response to the first circle (appearing after plate 21) was compared with the responses to the previous 19 Cs. The test was administered to 20 volunteer pseudomalingerers and 15 patients believed to be true malingerers. RESULTS: Malingering was detected in 14 (74%) of 19 volunteers included in the evaluation and in 12 (80%) of 15 patients by too many or too few correct answers to the stimuli or by their response to one of the circles. CONCLUSIONS: This test is useful in proving malingering. It may also provide evidence of a minimum visual recognition acuity within the gross dimension of the actual acuity.
OBJECTIVE: To describe a visual acuity test for use in identifying psychogenic visual impairment and malingering. METHODS: The test contained 32 white plates with a black Landolt C printed in the center. The sequence of the 4 alternative directions of the C was not predictable. After plate 21, 4 circles were interspersed among the remaining plates. The test is administered at a distance from which the subject is presumed to be able to recognize the optotypes. He or she is requested to identify the direction of the C within 2 seconds, and the responses are noted. Two elements were evaluated: (1) The number of correct answers was compared with the corresponding value of the distribution function of the binomial formula that represents the probability of reaching this rate of correct answers by pure chance. (2) The response to the first circle (appearing after plate 21) was compared with the responses to the previous 19 Cs. The test was administered to 20 volunteer pseudomalingerers and 15 patients believed to be true malingerers. RESULTS: Malingering was detected in 14 (74%) of 19 volunteers included in the evaluation and in 12 (80%) of 15 patients by too many or too few correct answers to the stimuli or by their response to one of the circles. CONCLUSIONS: This test is useful in proving malingering. It may also provide evidence of a minimum visual recognition acuity within the gross dimension of the actual acuity.