Abstract: An improved visual performance tester is provided which measures and stores very precise information concerning the visual sensitivity of a human eye, by use of a series of contrasting images on a computer monitor screen under a controlled-lighting environment. The tester measures the time it takes for a human patient to give the answers required by the test, thereby providing more accurate information than previously available in conventional vision testing systems. Various charts having different spatial frequencies (i.e., different sizes of bands inside a circle), different band inclinations, and different contrast characteristics are periodically displayed on the computer monitor, while the patient presses buttons (or areas) on the monitor screen to indicate his or her ability to perceive the chart images. By gradually and randomly decreasing the contrast, and/or increasing the spatial frequency, the tester can determine the patient's critical vision threshold.