Effect of pupil size on visual function under monocular and binocular conditions in LASIK and non-LASIK patients.

Purpose: To compare binocular and monocular vision in patients treated with laser in situ keratomileusis (LASIK) and in non-LASIK patients. Setting: Jules Stein Eye Institute, Los Angeles, California, USA. Methods: This comparative cross-sectional study comprised 20 postoperative LASIK patients and 20 non-LASIK ametropic patients. LogMAR visual acuity, contrast sensitivity, and infrared pupillometry were tested. Outcome measures were better-eye monocular acuity, binocular acuity, better-eye contrast sensitivity, binocular contrast sensitivity, and pupil diameter under monocular and binocular conditions. Results: Binocular visual acuity and contrast sensitivity were statistically significantly better than the visual acuity in the better eye (P =.0047 to <.0001) in both patient groups. Pupil diameter was statistically significantly smaller under the binocular condition than the monocular condition (P <.0001) in both groups. Conclusions: Monocular testing induced larger pupil diameters, which was associated with reduced vision compared to binocular measurements in LASIK and non-LASIK patients.