We measured response time, the number of nonresponses, response error, and subjective visibility evaluation for color Landolt-Cs with a gray color background presented on a CRT display to young and old adults (mean ages: 22.3 and 65.9 years, respectively) and to the same young adults wearing glasses with filters simulating an aging human crystalline lens. Comparing the results of elderly and young subjects without the filter, the results of the elderly subjects showed a longer response time, higher nonresponse ratio, slower response speed, and lower visibility, particularly for gray and blue stimuli. Conversely, the results for the young subjects who were fitted with the filters showed tendencies similar to those of the elderly subjects. These results indicate that the yellowing of the human lens strongly influences the visibility of color targets in the elderly and that wearing the filters enables young adults to simulate the visibility of the elderly. It suggests that the simulated filter as well as the aging human lens modifies the effective luminance, effective luminance contrast, and color difference between the color target and the background on the retina. Moreover, the relationship between the subjective evaluation and the response speed changes remarkably with age, regardless of the filters, suggesting that not only the subjective evaluation but also the evaluation of the performance, such as response speed, is important in estimating visibility and controllability in the elderly. The filter used in the present study will be an effective tool for the young to evaluate the visibility of elderly adults in terms of both response speed and subjective evaluation of visibility. (C) 2004 Wiley Periodicals, Inc.