The Value of Eccentric Infrared Photorefraction in Evaluating Keratoconus

This study aimed to determine the profile of eccentric, infrared photorefraction in keratoconus as a prototypical disease model for distorted corneas and identify a parameter in this profile for differentiating such disease conditions from healthy controls. METHODS Photorefraction reflex of 75 eyes with forme fruste to advanced keratoconic cases and that of 75 eyes of controls with regular refractive errors (spherical equivalent, +0.50 to −11.75 D; astigmatism, −0.50 to −4.50 D across 0 to 180° axes) were obtained over their natural pupils under unaided viewing using a custom-designed photorefractor placed at 1 m from the subject. The test was repeated in 10 controls with 4 and 6 D of trial-lens–induced myopia and myopic astigmatism at 0, 90, 45, and 135°. Linear regression was performed on the luminance profile across the pupil, and the departure of the data from linearity was estimated using the average residual error of the fit (Resavg). RESULTS Photorefraction profiles varied linearly across the pupil in controls, with slopes increasing with refractive error (r = 0.87; P .4). Corresponding profiles in keratoconus significantly departed from linearity, with Resavg progressively increasing with disease severity (r = 0.66; P
Source: Optometry and Vision Science - Category: Opthalmology Tags: ORIGINAL INVESTIGATIONS Source Type: research