Abstract

The contrast sensitivity function (CSF) is becoming increasingly popular as a clinical test for detecting and diagnosing eye disease. But the value of this test in predicting visual performance has received little attention. We have reported¹ that functional classifications of vision loss in terms of clarity of the ocular media and integrity of the central visual fields are predictive of reading performance. If the CSF is to be useful in predicting reading performance, we would expect these functional classifications to be reflected in properties of the CSF. We measured CSFs for thirty low-vision subjects using a forced-choice procedure. Spatial frequencies in the range 0.1-6 cycles/deg were tested. Observers with cloudy media and intact central fields show an increasing loss of contrast sensitivity with spatial frequency, compared to normal CSFs. Observers with clear media and central field loss show substantial loss of contrast sensitivity at all spatial frequencies, but the loss is greatest at high and low frequencies. Observers with peripheral field loss and clear or cloudy media show results that are intermediate between those of the two previous groups—sensitivity loss at both high and low spatial frequencies, with the high-frequency loss being greater. The differences between groups can be explained in terms of optical factors such as blur and nonoptical factors such as spatial summation.

© 1985 Optical Society of America