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Prediction of Mean Corneal Power Change After Pterygium Excision

Kim, Sun Woong MD, PhD; Park, Saemi MD; Im, Chan Young MD; Seo, Kyoung Yul MD, PhD; Kim, Eung Kweon MD, PhD

doi: 10.1097/ICO.0000000000000036
Clinical Science

Purpose: The aim of this study was to predict the mean corneal power change preoperatively for simultaneous pterygium excision and cataract extraction.

Methods: This study was performed in 2 stages. First, 66 eyes undergoing pterygium excision were recruited, and the subjects were divided into 2 groups based on a pterygium length of 2.0 mm (group 1: <2.0 mm, group 2: ≥2.0 mm). Keratometric values (K) were measured before, 1 month after, and 3 months after surgery. Multiple regression analyses were used to predict the postoperative mean K using preoperative K and morphological factors that significantly affect corneal power change. In the second stage, the regression equation was applied to 50 eyes (23 with pterygium <2.0 mm and 27 with pterygium ≥2.0 mm) in several clinics. Prediction accuracy was graded based on the difference between the calculated mean K and the postoperative mean K.

Results: In group 1, the mean Ks did not change significantly after the surgery, and therefore, the predicted mean K was not statistically different from the preoperative mean K. In group 2, the horizontal and mean Ks steepened significantly, and the regression analysis predicted the mean K within the range of 0.5 diopter difference in 22 of 31 eyes, showing a better approximation compared with the preoperative mean K (P < 0.001). The prediction accuracy was verified similarly in other clinics, and the regression analysis was useful for pterygium exceeding a length of 2.0 mm.

Conclusions: Pterygium exceeding a length of 2.0 mm induced a significant corneal power change after surgery. The mean K predicted from the regression analysis could be used as an approximation for a simultaneous pterygium and cataract surgery.

Supplemental Digital Content is Available in the Text.

*Department of Ophthalmology, Hando Hospital, Ansan, Korea;

Department of Ophthalmology, Soonchunhyang University Hospital, Bucheon, Korea;

Ian Eye Center, Seoul, Korea;

§Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea; and

Corneal Dystrophy Research Institute, Severance Biomedical Science Institute, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea.

Reprints: Eung Kweon Kim, Department of Ophthalmology, Yonsei University College of Medicine, 134, Shinchondong, Seodaemungu, CPO Box 8044, Seoul, Korea (e-mail:

Supported by the Converging Research Center Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (2012K001354).

The authors have no funding or conflicts of interest to disclose.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (

Received June 01, 2013

Accepted October 21, 2013

Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.