Abstract
To evaluate ocular straylight before and after photorefractive keratectomy (PRK) for low myopia with and without topical mitomycin (MMC) treatment. Patients who underwent PRK for low myopia were enrolled into the study. PRK without MMC was performed in 21 eyes (12 patients), whereas PRK with topical 0.02% MMC was performed in 25 eyes (14 patients). Both groups were treated using the NIDEK EC5000 excimer laser. Measurements were performed using the C-Quant straylight meter preoperatively and at two and four months postoperatively. The mean patient age was 30 ± 4 years, and the mean spherical equivalent refractive error was -2.2 ± 0.75 D. The mean preoperative intraocular straylight values were 1.07 ± 0.10 in the PRK without MMC group and 1.07 ± 0.11 log(s) in the PRK with topical MMC group. At two months after surgery, there was a decrease in mean intraocular straylight values in both groups. However, a significant difference was only reached in the PRK with MMC group [0.98 ± 0.09 log(s), p=0.002] compared with preoperative values, which was likely due to a greater scatter of measurements in the PRK without MMC group [1.03 ± 0.13 log(s), p=0.082]. At four months postoperatively, ocular straylight values were not significantly different compared with those at baseline in either the PRK without MMC group [1.02 ± 0.14 log(s), p=0.26] or in the PRK with topical MMC group [1.02 ± 0.11 log(s), p=0.13]. PRK for low myopia decreases ocular straylight, and MMC application further reduces straylight in the early postoperative period. However, ocular straylight values do not significantly differ at four months after surgery compared with those at baseline.
Highlights
Cornea laser refractive surgery has become generally accepted as a safe approach for correcting low-to-moderate refractive errors, and satisfactory visual acuity outcomes have been widely reported[1]
photorefractive keratectomy (PRK) surgery without MMC was performed in 21 eyes of 12 patients and PRK surgery with topical 0.02% MMC was performed in 25 eyes of 14 patients
At two months after surgery, there was a decrease in the mean intraocular straylight values in both groups compared with those at baseline; a significant difference was observed only in the PRK with MMC group (p=0.002) and not in the PRK without topical MMC group (p=0.082)
Summary
Cornea laser refractive surgery has become generally accepted as a safe approach for correcting low-to-moderate refractive errors, and satisfactory visual acuity outcomes have been widely reported[1]. The quality of vision may be altered due to changes in contrast sensitivity, glare, and/or higher-order aberrations[2]. Many previous studies have shown that corneal laser surgery impacts postoperative corneal aberrations and contrast sensitivity[3,4]. Relatively little work has focused on glare, despite patients frequently reporting this as a troubling symptom, at least in the early postoperative period, following procedures such as photorefractive keratectomy (PRK). Disability glare is the veiling of vision due to the forward scattering of light in the eye[5,6]. Straylight is a known source of disability glare[7]. Injury to the epithelium and re moval of the central epithelial basement membrane, which occur in PRK, initiate a complex sequence of events mediated by Submitted for publication: June 10, 2015 Accepted for publication: November 13, 2015
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