Corneal irregular astigmatism and contrast sensitivity after photorefractive keratectomy

Objective: To investigate the relation between contrast sensitivity and cor neal irregular astigmatism in eyes after photorefractive keratectomy (PRK). Design: Prospective observational case series. Participants and Controls: Seventy-nine eyes without corneal haze 6 months or more after PRK and 30 normal control eyes. Methods: Videokeratography was taken with TMS-1 (Computed Anatomy Inc. New York, NY), and contrast sensitivity for day and night vision was measured u sing a Multivision Contrast Tester 8000 (Vistech Consultants, Inc., Dayton, OH). Main Outcome Measures: Regular and irregular astigmatism (asymmetry and hig her order irregularity components) were computed using Fourier series harmo nic analysis of the videokeratography data. Area under the log contrast sen sitivity function (AULCSF) was calculated from the contrast sensitivity dat a taken at five spatial frequencies. Results: After PRK, AULCSFs were significantly smaller for day vision (P = 0.007, unpaired t test) and night vision (P = 0.020) compared with normal c ontrols. AULCSFs for day vision were significantly negatively correlated wi th asymmetry (Pearson's correlation coefficient, R = -0.23, P = 0.049) and higher order irregularity (R = -0.33, P = 0.004) components but not with th e regular astigmatism component (P > 0.3): AULCSF for night vision correlat ed significantly with asymmetry (R = -0.31, P = 0.013) and higher order irr egularity (R = -0.30, P = 0.016) components but not with the regular astigm atism component (P > 0.3). Conclusions: Corneal irregular astigmatism after PRK significantly influenc es contrast sensitivity. (C) 2001 by the American Academy of Ophthalmology.