The airtight Landolt-C - a handy test in the diagnosis of suspected ocularmalingering

Purpose: We present a visual acuity test for proof of malingering and psych ogenic impairment of visual acuity. Method: The book contains 36 plates. On 32 plates, a Landolt-C is shown wit h a gap of 10 minutes of are, thus corresponding to a visual acuity of 0.1, when applied at a distance of 1 metre. Each of the 4 alternative of the La ndolt-C occurs eight times in random order. Starting at position 21, four p lates are interspersed showing a closed circle of the same size. The test i s used at a distance corresponding to an acuity level of maximum 50% of the presumed factual acuity. Following a four alternative forced choice paradi gm, the tested person is requested to call the direction of the Landolt-C w ithin about 2 seconds, when the plates of the book are turned over. The res ponses and their latency are recorded using a digital electronic system whi ch allows later audiovisual analysis. The response on the first closed circ le and its latency is compared to the previous responses. Two subjects were tested who tried to pretend a reduction of their visual acuity. Results: Malingering was proved by the verbal response of the first subject and by the long latency of the response of the second subject (4.0 s vs. 1 .2 s-2.7 s for the previous responses). The entire test, explanation includ ed, took less than 5 minutes. Conclusion: This handy test can be a useful tool in cases suspect of maling ering or psychogenic impairment of visual acuity.