Contrast Sensitivity and Glare Disability After Radial Keratotomy and Photorefractive Keratectomy

Abstract

MOST CLINICAL studies assess the safety of refractive surgical procedures by measuring the change in best spectacle-corrected visual acuity. Visual acuity, however, is a crude measure of visual performance. Visual acuity is usually measured by determining a person's ability to resolve fine spatial detail using high-contrast targets (black figures on a white background), such as Snellen letters, numbers, or Landolt C rings. The contrast level of these targets approaches 100%. In everyday life, however, such high-contrast targets are rarely encountered, and patients who score well on traditional visual acuity tests may complain of poor vision in everyday situations.¹ Such patients are believed to have decreased contrast sensitivity (CS), which impairs their ability to identify objects with low contrast under low lighting conditions.