Measurement of glare susceptibility using low-contrast letter charts.

The Committee on Ophthalmic Procedures Assessment of the American Academy of Ophthalmology suggested either contrast sensitivity or low-contrast visual acuity (VA) measured before and after adding a glare source as a test for assessing overall visual disability from immature cataracts. We have developed a test that follows the Committee's three principles of design, and we report that the effect of glare on VA is considerably greater for recognizing low-contrast letters than for recognizing high-contrast letters. The effect of glare on VA increases progressively as letter contrast is reduced from 96% through 50%, 25%, 11%, and 4%. The 25% chart (and possibly the 11% chart) gives the most suitable sensitivity for eyes with immature cataracts. Neither age-related brunescence and aging itself nor even the presence of a distinct opacity necessarily produces high sensitivity to glare. The test is sensitive enough to detect an ageing effect even before the age of 45 to 55 years and to reveal large intersubject differences among normally sighted 19- to 25-year-old subjects.