Stray light in radial keratotomy and the influence of pupil size and straylight angle

Glare is a major sequela of the radial keratotomy procedure. We used the straylight meter to measure intraocular light scatter, which is the cause of glare, in eyes after radial keratotomy. This apparatus uses a direct compensation method to assess the amount of intraocular light scatter. Nineteen patients were tested. Nine individuals served as controls. The mean postsurgery time was 60 months. The influence of the number of radial incisions, the pupil size, and the angle of light entering the eye were evaluated with the straylight meter. The results showed straylight values for normal pupil size (mean, 4 mm) to be statistically significantly higher (P = .0044) only for the smallest angle of light deflection studied (3.5 degrees). For dilated pupils (mean, 8 mm), straylight values were statistically significantly higher (P = .00005) for all three angles of light deflection studied. The number of incisions showed no statistically significant relationship to straylight values. Average stray light values were increased by a factor of 1.4 for 4-mm sized pupils and 2.0 for 8-mm sized pupils. There was an overlap in straylight values between the patient population and the control population.