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Kim and Kim: Comparison of Corneal Higher-order Aberration before and after Excision of Pterygium
Original Article

Journal of the Korean Ophthalmological Society 2017; 58(9): 1023-1030.

Published online: 18 September 2017

DOI: https://doi.org/10.3341/jkos.2017.58.9.1023

Comparison of Corneal Higher-order Aberration before and after Excision of Pterygium

Bong Jun Kim, MD, Sun Woong Kim, MD, PhD

Department of Ophthalmology, Yonsei University Wonju College of Medicine, Wonju, Korea.

Address reprint requests to: Sun Woong Kim, MD, PhD. Department of Ophthalmology, Wonju Severance Christian Hospital, #20 Ilsan-ro, Wonju 26426, Korea. Tel: 82-33-741-1346, Fax: 82-33-741-0460, eyedockim@yonsei.ac.kr

Received 15 June 2017       Revised 27 July 2017       Accepted 23 August 2017

©2017 The Korean Ophthalmological Society

The Korean Ophthalmological Society

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To investigate the types of corneal higher-order aberration (HOA) induced by pterygium, residual corneal HOA after pterygium surgery, and correlations between corneal HOA and the length of the pterygium.

Methods

Fifty-three patients who underwent pterygium excision with conjunctival autograft were enrolled. Corneal HOA was measured by Pentacam® (Oculus Inc., Wetzlar, Germany) preoperatively and 3 months postoperatively in the 6-mm optical zone. Preoperative and postoperative HOAs of eyes with pterygium were compared with HOAs of the fellow eye to evaluate HOAs induced by pterygium and residual HOAs after pterygium surgery. Partial correlation analysis was performed to investigate the relationship between HOAs and the length of pterygium. A postoperative HOA less than 0.35 µm in size was defined as a favorable surgical outcome and the surgical indications were estimated using receiver operator characteristic (ROC) curve.

Results

Horizontal coma, root mean square (RMS) of coma, oblique trefoil, horizontal trefoil, RMS of trefoil, and total HOA were significantly greater in the eye with preoperative pterygium. Three months after pterygium excision, only RMS of coma and total HOA remained significantly greater in eyes with pterygium. Vertical coma, horizontal coma, RMS of coma, and oblique tetrafoil were correlated with pterygium length. Pterygium excision when pterygium length was less than 1.6 mm led to favorable surgical outcomes.

Conclusion

Pterygium induced greater than third-order corneal HOAs and these HOAs were corrected via pterygium surgery. Longer pterygium length was associated with larger RMS of coma and larger coma RMS persisted after pterygium surgery. A pterygium length of 1.6 mm should be considered the cutoff for pterygium excision for reducing postoperative corneal HOA.

Keywords: Corneal aberration, Excision of pterygium, Higher-order aberration, Pentacam, Pterygium

Figures and Tables

Figure 1

Preoperative slit-lamp photograph of the pterygium. Gray dashed lines were added to the image analysis for the measurement of length of pterygium. Length of pterygium (double-headed arrow): distance between the two vertical lines to the horizontal line passing through the corneal center (a), one line (b) tangent to the pterygium head and second line (c) tangent to the corneal limbus.

jkos-58-1023-g001
Figure 2

Receiver operator characteristic (ROC) curve for postoperative higher-order aberration under 0.35 µm versus length of pterygium. Std. = standard; Sig. = significance.

jkos-58-1023-g002
Table 1

Demographic characteristics of subjects who received excision of pterygium

jkos-58-1023-i001

Values are presented as mean ± SD unless otherwise indicated.

Table 2

Bilateral comparison of higher-order aberration in pterygium eyes and control eyes before pterygium surgery

jkos-58-1023-i002

Values are presented as mean ± SD unless otherwise indicated.

HOA = higher-order aberration.

Table 3

Bilateral comparison of higher-order aberration in pterygium eyes following pterygium surgery and control eyes

jkos-58-1023-i003

Values are presented as mean ± SD unless otherwise indicated.

HOA = higher-order aberration.

Table 4

Higher-order aberration of pterygium eyes before and after pterygium surgery

jkos-58-1023-i004

Values are presented as mean ± SD unless otherwise indicated.

HOA = higher-order aberration.

Table 5

Partial correlation analysis between higher-order aberration and length of pterygium

jkos-58-1023-i005

Controlled by age and sex.

HOA = higher-order aberration; Induced HOA = preoperative HOA of pterygium eyes – HOA of control eyes; Remained HOA = postoperative HOA of pterygium eyes – HOA of control eyes.

Table 6

Partial correlation analysis between higher-order aberration and width of pterygium

jkos-58-1023-i006

Controlled by age and sex.

HOA = higher-order aberration; Induced HOA = preoperative HOA of pterygium eyes – HOA of control eyes; Remained HOA = postoperative HOA of pterygium eyes – HOA of control eyes.

Table 7

Specificity, sensitivity identified by cutoff points of lengh of pterygium

jkos-58-1023-i007

Notes

Conflicts of Interest The authors have no conflicts to disclose.

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