ARTICLE Intraocular Straylight and Contrast Sensitivity 1 /2 and 6 Months After Laser In Situ Keratomileusis Amalia Lorente-Vela ´zquez, Ph.D., Amelia Nieto-Bona, M.Sc., Ce ´sar Villa Collar, M.Sc., and Angel Ramo ´n Gutierrez Ortega, Ph.D. Objectives: To compare intraocular straylight and contrast sensitivity determined before and 15 days and 6 months after laser keratomileusis. Methods: 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 sur- gery) 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 Treat- ment Diabetic Retinopathy Study charts (LogMAR units). All measure- ments were obtained over time and compared. Results: 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 con- trast sensitivity or BSCVA and intraocular straylight were observed 15 days and 6 months after LASIK. Conclusions: 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. Key Words: Cornea—Intraocular straylight—Contrast sensitivity—LASIK. (Eye & Contact Lens 2010;3: 152-155) I t is well known that disability glare is a consequence of intraocular straylight. 1–3 In a normal eye, the main contribut- ing factors to the total amount of straylight are the cornea, iris and sclera, crystalline lens, and fundus. Intraocular light scat- tering increases with age, but this effect is much greater in subjects with cataracts. 4,5 Previous studies have also shown that light scattering by the cornea changes after refractive surgery. 6–8 Light scattering re- duces the contrast of the image projected on the retina, thus decreasing vision quality. Even when visual acuity is 20/20 after the surgery, corneal light scattering can be a cause of dissatisfac- tion for the patient, with most discomfort at night experienced especially while driving. Night-vision disturbances occur fre- quently and their incidence is highly variable. 9 Van den Berg designed an instrument, the straylight meter, which measures forward light scatter and provides direct information on optical imperfections as the cause of disability glare. 10,11 The use of this device to measure straylight has been reported after laser in situ keratomileusis (LASIK) and photorefractive keratectomy 8 in pa- tients with cataract and after lens extraction 5 and in patients with contact lenses 12 and intraocular lenses. 13,14 In a previous study, 8 the authors noted that on average straylight values did not increase 1 month after LASIK or photorefractive keratectomy, although individual values increased in same cases. We decided to examine possible changes in intraocular straylight 15 days and six months after surgery using the straylight meter. Vignal et al. 15 determined the influence of straylight on contrast acuity after laser surgery. Because this measure is insufficient to characterize the visual performance of the eye, we were also interested in determining the effect of straylight on contrast sen- sitivity. This function is an important diagnostic tool used to assess visual deficits and visual performance 16 and has proved especially useful in patients who have undergone corneal laser refractive surgery. 17 MATERIALS AND METHODS Twenty-three white patients (46 eyes) were enrolled, and 39 eyes of 20 patients were finally included in the study after applying the inclusion criteria. These were a refractive error before surgery of less than -6.00 D of myopia and -2.00 D of astigmatism, age 21 to 40 years, normal eye health, and no ocular or systemic disease. Best spectacle-corrected visual acuity (BSCVA) must be at least 0.04 LogMAR. Informed consent for participation was obtained from each subject. The study protocol adhered to the tenets of the Declaration of Helsinki. The study was approved by Clinical Research Ethics Committee of the School of Optometry. A full ophthalmologic examination was performed in which we determined uncorrected visual acuity (UCVA), BSCVA, manifest From the Department of Optics II (A.L.-V., A.N.-B.), University School of Optics, University Complutense of Madrid; Clinicas Novovision (C.V.C.), Madrid, Spain; and University of Murcia (A.R.G.O.), Murcia, Spain. Supported in part by the Red Tema ´tica Optometría Ministerio de Ciencia e Innovacio ´n (Acciones Complementarias SAF2008 – 01114-E). The authors declare no financial or proprietary interests in any materials or methods mentioned. Address correspondence and reprint requests to Amalia Lorente- Vela ´zquez, Ph.D., Department of Optics II, University School of Optics, University Complutense of Madrid, Arcos de Jalon s/n, 28037 Madrid, Spain; e-mail: alorente@opt.ucm.es Accepted February 19, 2010. DOI: 10.1097/ICL.0b013e3181d9ee21 152 Eye & Contact Lens • Volume 36, Number 3, May 2010