Quantitative Assessment of Disability Glare

Abstract

Abstract: : Excimer laser surgery (LASIK and PRK) is effective for correction of refractive error, but many patients complain of glare, particularly at night. Since conventional glare testing often improves performance in refractive surgery patients (by constricting the pupil and decreasing the effects of peripheral aberrations), quantification of these symptoms is lacking. Purpose: We describe theory and application of a new approach to quantify disability glare, which overcomes problems of current techniques, by combining low luminance, small target contrast sensitivity (CS) with diffuse glare. We report findings for controls subjects and patients treated successfully with PRK at least one year ago. Methods: Small letter CS comprised of letters of constant, small size (20/25), which vary in contrast (0.1 log steps per row; 0.01 per letter), was presented at low luminance (3 cd/m₂), with and without diffuse surrounding glare (315 cd/m ₂), and under standard photopic conditions (150 cd/m₂). Pupil size was monitored with infrared pupillometry, and higher order ocular aberrations were assessed (WaveFront Sciences COAS). Results: In contrast to results with conventional glare tests, CS was significantly decreased in PRK subjects in the presence of glare (mean decrease 2.9 lines), which caused minimal decrease in pupil size (<1mm). While performance in this sample of PRK subjects was not significantly different from normal (p=0.2), there was an inverse relation between CS and pupil size (p<0.01), and individuals with pronounced disability glare showed specific increases in higher order aberrations (coma in PRK; trefoil and spherical aberration in controls). Conclusion: Disability glare can be quantified in refractive surgery as well as normal eyes by assessment of low luminance, small target CS, with and without surrounding glare. Pupillary constriction is minimized, and CS is consistently reduced in the presence of glare. Performance decrements can be linked to specific higher order ocular aberrations.

Keywords: 550 refractive surgery: optical quality • 544 refractive surgery • 368 contrast sensitivity