Downloaded from http://journals.lww.com/corneajrnl by BhDMf5ePHKbH4TTImqenVJRkcJu5k+K7v/fe11GbfOi+o834jfWYD7DgS/B2F1sN on 06/13/2020 CLINICAL SCIENCE Posterior Corneal Surface Changes After Pterygium Excision Surgery Eliya Levinger, MD,*† Nir Sorkin, MD,*‡ Sara Sella, MD,†§ Omer Trivizki, MD,*† Matthew Lapira, MD, FRCOphth,¶ and Shay Keren, MD*† Purpose: To evaluate the effect of pterygium excision on the posterior corneal surface and analyze the factors associated with those changes. Methods: A prospective, interventional study including 33 eyes of 31 patients who underwent pterygium excision at the Tel Aviv Medical Center (Tel Aviv, Israel). Exclusion criteria included corneal dystrophy, pseudopterygium, corneal scarring, or previous ocular surgery in the treated eye. Data were obtained by using the Galilei dual Scheimpflug analyzer. Recorded posterior corneal data included steep keratometry, flat keratometry, mean keratometry, corneal astigmatism, best-fit sphere, and the squared eccentricity index (e 2 ). Posterior surgically induced astigmatism (SIA) was calculated to demonstrate the astigmatic effect of surgery. Anterior-segment high resolution optical coherence tomography was used to measure pterygium dimensions (depth and horizontal/vertical size). Results: The mean age was 53.7 6 16.7 years. Posterior corneal SIA was 0.9 6 1.1 D (P , 0.001) and was significantly correlated with age (r = 0.568, P = 0.002), horizontal pterygium size (r = 0.387, P = 0.046), and preoperative posterior astigmatism (r = 0.688, P , 0.001). In a multivariable analysis, only age (coefficient = 0.010, P = 0.038) and preoperative posterior astigmatism (coefficient = 0.648, P = 0.002) remained significant. Pterygium dimensions were not signifi- cantly associated with SIA magnitude. Flat keratometry steepened by 0.5 6 1.1 D (P = 0.019), mean keratometry steepened by 0.3 60.6 D (P = 0.035), posterior astigmatism was reduced by 0.4 6 1.2 D (P = 0.072), and e 2 decreased by 5.1 6 17.3 (P = 0.021). Conclusions: Pterygium excision has a significant astigmatic effect on the posterior corneal surface. The astigmatic effect increases with age and with higher preoperative posterior astigmatism. Pterygium depth and size are not associated with the degree of surgical astigmatic effect. Key Words: pterygium, cornea, posterior, astigmatism, refraction (Cornea 2020;39:823–826) T he pterygium is a wing-shaped fibrovascular conjunctival growth that extends onto the cornea, usually on the nasal side. 1,2 Pterygium can cause significant visual impairment, either because of the direct involvement of the visual axis or because of the changes in corneal shape and curvature. 1,3 Pterygium can affect topographic and refractive values, inducing with-the-rule or irregular astigmatism and increasing higher-order aberrations, mainly coma and trefoil types. 4 Most studies evaluating astigmatism and corneal- aberration changes after pterygium surgery used corneal topography to evaluate the anterior corneal surface alone. 1,3,5 The posterior corneal surface affects the total corneal astigma- tism by an average of 0.3 to 0.8 D and can be an essential component in astigmatism correction surgery and intraocular lens implantation. 6 One previous study evaluated the posterior corneal changes after pterygium excision, by using the Pentacam Scheimpflug tomographer (Oculus, Wetzlar, Ger- many), and showed no remarkable posterior corneal changes. It did however show a significant change in posterior astigmatism orientation, from against-the-rule to with-the-rule astigmatism, indicating a significant effect on astigmatism axis. 3 The Galilei dual Scheimpflug analyzer (GDA) (Ziemer, Port, Switzerland) uses a dual rotating Scheimpflug imaging system and a Placido disk to improve the accuracy of corneal measurements. To the best of our knowledge, the effect of pterygium excision on the posterior corneal surface has not been evaluated using the GDA and has not been analyzed previously using vectoral mathematics. In this study, we evaluated the effect of pterygium surgery on the posterior corneal surface using the GDA and vectoral calculations and analyzed factors associated with those changes. METHODS This prospective, interventional study included pa- tients who underwent pterygium excision at the Tel Aviv Medical Center (Tel Aviv, Israel) between June 2018 and December 2018. Exclusion criteria included corneal dystro- phy, pseudopterygium, corneal scarring, or previous ocular surgery in the treated eye. The study was approved by the research ethics board of the Tel Aviv Medical Center and was conducted in accordance with the principles of the Received for publication October 9, 2019; revision received February 6, 2020; accepted February 9, 2020. Published online ahead of print April 5, 2020. From the *Department of Ophthalmology, Tel Aviv Medical Center, Tel-Aviv, Israel; †Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel; ‡Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada; §Department of Ophthalmology, Meir Medical Center, Kefar-Saba, Israel; and ¶Oxford Eye Hospital, John Radcliffe Hospital, Oxford NHS Trust, Oxford, United Kingdom. The authors have no funding or conflicts of interest to disclose. Correspondence: Shay Keren, MD, Department of Ophthalmology, Tel-Aviv Medical Center, 6 Weizman St, Tel-Aviv 6423906, Israel (e-mail: shaykeren88@gmail.com). Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved. Cornea  Volume 39, Number 7, July 2020 www.corneajrnl.com | 823 Copyright © 2020 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.