Aims. This study investigated the effect of simulated visual impairment on the speed and accuracy of performance on a series of commonly used cognitive tests.Methods. Cognitive performance was assessed for 30 young, visually normal subjects (M 22.0 +/- 3.1 years) using the Digit Symbol Substitution Test (DSST), Trail Making Test (TMT) A and B and the Stroop Colour Word Test under three visual conditions: normal vision and two levels of visually degrading filters (Vistech (TM)) administered in a random order. Distance visual acuity and contrast sensitivity were also assessed for each filter condition.Results. The visual filters, which degraded contrast sensitivity to a greater extent than visual acuity, significantly increased the time to complete (p < .05), but not the number of errors made, on the DSST and the TMT A and B and affected only some components of the Stroop test.Conclusions. Reduced contrast sensitivity had a marked effect on the speed but not the accuracy of performance on commonly used cognitive tests, even in young individuals; the implications of these findings are discussed.