Real-Life Variability of Corneal Epithelium Thickness in Photorefractive Keratectomy

Abstract PURPOSE: To evaluate the real-life epithelial thickness (ET) as measured intraoperatively by optical coherence pachymetry (OCP) in myopic eyes undergoing alcohol-assisted photorefractive keratectomy (PRK).METHODS: A retrospective review of patients who underwent alcohol-assisted PRK was performed. Data were abstracted on age, gender, contact lens (CL) wear, preoperative refractive errors, keratometry, topographic and ultrasonic pachymetry, and intraoperative OCP measurements before and after epithelium removal. The central ET was calculated by subtracting OCP measurement after epithelium removal from the OCP measurement prior to epithelium removal. RESULTS: The study comprised of 140 consecutive eyes from 70 patients. The mean age was 27.29 ± 6.57 years, 51.4% were females. CL was used in 80 eyes (57.1%). The mean sphere and spherical equivalent were -3.69 ± 2.74D and -3.36 ± 2.76D, respectively. The mean intraoperative ET was 59.49 ± 19.93µm (range, 15-150µm). Fifty-four percent of the eyes had an ET measurement above or below the range of 40-60µm. ET was significantly higher in the second operated eye compared to the first operated eye (p=0.006). There was no significant difference in thickness between genders (p=0.29) or association to CL-wear (p=0.11), and no correlation to patient age (p=0.18, rp=0.13), refractive errors (p>0.11, rp=-0.02-0.14), nor keratometry (p>0.64, rp=-0.01-0.02). Conclusion: The real-life assessment of intraoperative ET in alcohol-assisted PRK showed a high variability of the central corneal epithelium, with a significant difference between the first and second operated eyes. This difference may have implications when the epithelium is not included in the surgical planning in surface ablation.