We investigated how induced blur affects performance on the Trail Making Test and Digit Symbol Test routinely used in occupational therapy cognitive evaluations. The study used a factorial design with both age (young and old adults) and simulated blur levels of near visual acuity (20/50 and 20/100) manipulated between participants. A sample of 124 healthy, community-living adults was used in the final analysis. Significant differences (p < .05) were found in performance for young participants between 20/50 and 20/100 blur level as well as between 20/20 and 20/100 blur level for the Digit Symbol Test. Scores for old participants decreased as a function of blur but were not significant. This study illustrates that cognitive evaluations used throughout the lifespan may require the appropriate visual acuity level to maximize performance. Occupational therapists’ understanding of client factors and their effect on performance is fundamental to the client evaluation process.