Better contrast sensitivity tests needed

This article reviews the importance of contrast sensitivity to vision and its role in identifying many ocular diseases, and compares the strengths and weaknesses of contrast sensitivity testing methods. The authors explain that testing the peak of contrast sensitivity function provides a useful clinical adjunct to standard visual acuity assessments.

They write that the Pelli-Robson and Mars letter charts are easy to use and reliable, although their results may be influenced by lighting, reflections and fading of the charts. In addition, patients' cognitive ability to recognize patterns can affect whether they correctly identify a letter. Tests that use gratings eliminate the confounding factors of language and intelligence from their results, but they have poor reliability.

The authors conclude that it is important for a contrast sensitivity testing method to have strong reliability to differentiate normal from abnormal and to determine whether progression is real. They say that an ideal contrast sensitivity test would evaluate peak contrast sensitivity function, be reliable and not be influenced by language ability.