Intraocular straylight and contrast sensitivity (1/2) and 6 months after laser in situ keratomileusis

To compare intraocular straylight and contrast sensitivity determined before and 15 days and 6 months after laser keratomileusis.

A single-centre, prospective, longitudinal randomized trial was performed on 20 subjects undergoing refractive surgery. In each subject, best spectacle-corrected visual acuity (BSCVA) and straylight and contrast sensitivity were determined preoperatively (on the day of refractive surgery) and then after laser in situ keratomileusis (LASIK) surgery in the 15-day and 6-month follow-up visits. Straylight was measured using the van den Berg straylight meter (third generation). Contrast sensitivity was determined under photopic and mesopic conditions using the VCTS 6500 (Vision Contrast Test System). BSCVA was measured using Early Treatment Diabetic Retinopathy Study charts (LogMAR units). All measurements were obtained over time and compared.

Straylight values (mean +/- SD) were 0.99 +/- 0.03, 0.88 +/- 0.03, and 0.93 +/- 0.03 before and (1/2) and 6 months after LASIK surgery. These values significantly fell from preoperative levels to those recorded 15 days after LASIK (P = 0.03) although values at 6 months failed to differ from baseline (P>0.05). Photopic and mesopic contrast sensitivity measured at several spatial frequencies remained stable. No correlations between contrast sensitivity or BSCVA and intraocular straylight were observed 15 days and 6 months after LASIK.

Intraocular straylight was reduced 15 days after surgery although by 6 months values returned to preoperative levels. These changes in straylight values could not be related to changes in mesopic and photopic contrast sensitivity or BSCVA during the follow-up period.