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Han, Kim, and Lee: The Changes of Corneal Higher-Order Aberrations after Surgery According to Pterygium Size
Original Article

J Korean Ophthalmol Soc 2014;55(1):32-39.

Published online: 7 September 2014

DOI: https://doi.org/10.3341/jkos.2014.55.1.32

The Changes of Corneal Higher-Order Aberrations after Surgery According to Pterygium Size

Hyun Cheol Han, MD, Jin Hyoung Kim, MD, PhD, Do Hyung Lee, MD, PhD

Department of Ophthalmology, Ilsan Paik Hospital, Inje University College of Medicine, Goyang, Korea

Address reprint requests to Do Hyung Lee, MD, PhD Department of Ophthalmology, Ilsan Paik Hospital, #170 Juhwa-ro, Ilsanseo-gu, Goyang 411-706, Korea, Tel: 82-31-910-7240, Fax: 82-31-911-7241, E-mail: eyedr0823@hotmail.com

Received 15 June 20136 September 2013       Accepted 20 November 2013

Copyright © 2014 Korean Ophthalmological Society

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 effects of pterygium size on the change of corneal astigmatism and corneal higher-order aberrations (HOAs) after surgery.

Methods

Fifty eyes of 46 patients who underwent pterygium surgery were included in the present study and divided into 2 groups according to pterygium size (small group: size ≤ 2.0 mm, large group: size > 2.0 mm). Corneal HOAs using wavefront aberrometer (KR-1W®) and corneal astigmatism using topography (Orbscan II®) were evaluated before surgery and their changes monitored after surgery at postoperative 1 week, 1 month, and 3 months.

Results

The small group was comprised of 16 eyes and 34 eyes were included in the large group. In the small group, uncorrected visual acuity (UCVA), best corrected visual acuity (BVCA), and spherical equivalent (SE) were not statistically significantly different after surgery at postoperative 3 months. In the large group, BVCA was not statistically significantly different, but UCVA increase and SE decrease were statistically significant after surgery at postoperative 3 months. Preoperative simulated keratometric (Sim K) astigmatism and corneal HOAs increase were statistically significant according to the pterygium size. Preoperative corneal HOAs of the large group were significantly higher than the small group except for spherical aberration in the central 4 mm optical zone (p = 0.501). In the small group, there was no statistically significant difference in corneal HOAs before and after surgery. In the large group, corneal total HOAs, trefoil and coma in the central 4 mm and 6 mm zone were statistically significantly decreased at postoperative 1 week, 1 month, and 3 months, re-spectively (p < 0.05).

Conclusions

The corneal HOAs and the corneal astigmatism were increased according to pterygium size. In cases with pterygium greater than 2.0 mm in size, the corneal HOAs and the corneal astigmatism were decreased after pterygium surgery which can improve visual acuity and quality. Therefore, the pterygium size can be a useful factor in deciding when to perform pterygium surgery.

Keywords: Higher-Order Aberrations, Pterygium, Topography, Visual Acuity, Wavefront

References

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Figure 1.
Pterygium size was measured at the slit lamp with the eye in the primary position and the area was calculated by image J program.
jkos-55-32f1.tif
Figure 2.
Mean SE (D), UCVA and BCVA (Snellen chart) changes at 3 months after surgery. (A) Small pterygium group, (B) Large pterygium group. * SE showed statistically significant decrease and UCVA showed statistically significant increase at 3 months after surgery (p = 0.035, p = 0.008 by paired t-test). D = diopter; UCVA = uncorrected visual acuity; BCVA = best corrected visual acuity; SE = spherical equivalent.
jkos-55-32f2.tif
Figure 3.
The mean change of Sim K (Simulated Keratometry) astigmatism. * There were significant decrease in Sim K astigmatism at 1 week, 1 month, and 3 months after surgery in large pterygium group (p = 0.015, p = 0.005, p = 0.002 by Paired t-test). D = diopter.
jkos-55-32f3.tif
Figure 4.
The changes of mean corneal higher-order aberrations at 1 week, 1 month, and 3 months after surgery in large pterygium group. * Corneal total, trefoil, and coma HOAs in the central 4 mm & 6 mm zone were statistically significantly decreased at 1 week, 1 month, and 3 months compared with those before surgery (p < 0.05 by Paired t-test, respectively).
jkos-55-32f4.tif
Table 1.
Baseline characteristics
  Small pterygium group (n = 16) Large pterygium group (n = 34) p-value* (p < 0.05)
Sex (M/F) 10/6 16/18 0.238
Age (years) 62.3 ± 12.96 64.2 ± 9.63 0.592
Size (mm) 1.68 ± 0.31 3.70 ± 0.99 <0.001†
Area (mm2) 5.02 ± 1.37 14.96 ± 4.31 <0.001†
UCVA 0.82 ± 0.24 0.53 ± 0.33 0.007†
BCVA 0.85 ± 0.25 0.76 ± 0.28 0.309
SE (D) 0.72 ± 0.88 0.71 ± 1.59 0.975
Sim K astigmatism (D) -0.58 ± 0.28 -3.05 ± 2.60 <0.001†

Values are presented as mean ± SD.

UCVA = uncorrected visual acuity; BCVA = best corrected visual acuity; SE = spherical equivalent; Sim K = simulated keratometry.

* Carried out using independent samples t-test except in the case of p-value of sex was carried out using chi square test

† Size, area, UCVA and Sim K astigmatism of large pterygium group were statistically significantly higher than those of small pterygium group before surgery.

Table 2.
Correlation between the corneal higher-order aberrations and the size of the pterygium before surgery
  Correlation (r) p-value (p < 0.05)
Mean Sim K astigmatism (D) 0.681 <0.001*
4 mm Total (μm) 0.628 <0.001*
4 mm Trefoil (μm) 0.583 <0.001*
4 mm Coma (μm) 0.421 0.003*
4 mm Spherical (μm) 0.125 0.402
6 mm Total (μm) 0.641 <0.001*
6 mm Trefoil (μm) 0.528 <0.001*
6 mm Coma (μm) 0.368 0.011*
6 mm Spherical (μm) 0.409 0.004*

Correlations were carried out using pearson correlation test.

Sim K = simulated keratometry.

* Sim K astigmatism was statistically significantly increased according to the size of pterygium before surgery. Corneal total HOAs, trefoil, coma in the central 4 mm & 6 mm zone and spherical in the central 6 mm zone were statistically significantly increased according to the size of pterygium before surgery.

Table 3.
Comparison of the corneal higher-order aberrations between small and large pterygium group before surgery
  Small pterygium group Large pterygium group p-value* (p < 0.05)
4 mm Total (μm) 0.244 ± 0.098 0.690 ± 0.418 <0.001†
4 mm Trefoil (μm) 0.140 ± 0.092 0.550 ± 0.396 <0.001†
4 mm Coma (μm) 0.149 ± 0.080 0.238 ± 0.148 0.012†
4 mm Spherical (μm) 0.032 ± 0.040 0.047 ± 0.104 0.501
6 mm Total (μm) 0.728 ± 0.271 1.593 ± 0.669 <0.001†
6 mm Trefoil (μm) 0.373 ± 0.232 1.066 ± 0.594 <0.001†
6 mm Coma (μm) 0.382 ± 0.206 0.548 ± 0.280 0.033†
6 mm Spherical (μm) 0.245 ± 0.114 0.360 ± 0.261 0.041†

Values are presented as mean ± SD.

SD = standard deviation.

* Carried out using independent samples t-test

† Corneal total HOAs, trefoil, coma in the central 4 mm & 6 mm zone and spherical in the central 6 mm zone of large group were statistically significantly higher than those of small group before surgery.

Table 4.
Mean simulated keratometry astigmatism according to the size of the pterygium before surgery
Size (mm) No. of eyes Astigmatism (D) p-value* (p < 0.05)
A: ≤2.0 16 -0.59 ± 0.28  
B: >2.0-≤3.0 9 -1.58 ± 1.183 A-B 0.025†
C: >3.0-≤4.0 14 -2.70 ± 2.46 B-C 0.224
D: >4.0 11 -4.71 ± 2.85 C-D 0.058
Total 50 -2.37 ± 2.47  

Values are presented as mean ± SD.

D = diopte.

* Carried out using independent samples t-test

† Mean simulated keratometry astigmatism of 2.0 mm or less group was statistically significantly lower than that of the other groups.

Table 5.
The changes of corneal higher-order aberrations before and after surgery in small pterygium group
  Pre-op 1 week 1 week p-value* 1 month 1 month p-value* 3 months 3 months p-value*
4 mm total (μm) 0.244 ± 0.098 0.287 ± 0.085 0.236 0.245 ± 0.109 0.968 0.244 ± 0.100 0.884
4 mm trefoil (μm) 0.140 ± 0.092 0.163 ± 0.092 0.587 0.151 ± 0.123 0.778 0.140 ± 0.100 0.996
4 mm coma (μm) 0.149 ± 0.080 0.146 ± 0.071 0.937 0.127 ± 0.071 0.424 0.142 ± 0.073 0.561
4 mm spherical (μm) 0.032 ± 0.040 0.017 ± 0.064 0.273 0.043 ± 0.055 0.456 0.032 ± 0.051 0.775
6 mm total (μm) 0.728 ± 0.271 0.635 ± 0.200 0.124 0.613 ± 0.134 0.093 0.604 ± 0.173 0.088
6 mm trefoil (μm) 0.373 ± 0.232 0.305 ± 0.215 0.275 0.284 ± 0.188 0.127 0.245 ± 0.163 0.055
6 mm coma (μm) 0.382 ± 0.206 0.302 ± 0.195 0.354 0.261 ± 0.192 0.131 0.311 ± 0.146 0.263
6 mm spherical (μm) 0.245 ± 0.114 0.213 ± 0.135 0.388 0.241 ± 0.113 0.918 0.222 ± 0.154 0.816

Values are presented as mean ± SD.

SD = standard deviation.

* Carried out using paired t-test (p < 0.05).

Table 6.
The change of corneal higher-order aberrations before and after surgery in large pterygium group
  Pre-op 1 week 1 week p-value* 1 month 1 month p-value* 3 months 3 months p-value*
4 mm total (μm) 0.690 ± 0.418 0.368 ± 0.179 <0.001† 0.359 ± 0.204 <0.001† 0.300 ± 0.161 <0.001†
4 mm trefoil (μm) 0.550 ± 0.396 0.247 ± 0.158 <0.001† 0.237 ± 0.203 <0.001† 0.189 ± 0.139 <0.001†
4 mm coma (μm) 0.238 ± 0.148 0.161 ± 0.089 0.002† 0.161 ± 0.086 0.001† 0.149 ± 0.084 0.001†
4 mm spherical (μm) 0.047 ± 0.104 0.037 ± 0.086 0.650 0.050 ± 0.070 0.883 0.038 ± 0.062 0.709
6 mm total (μm) 1.593 ± 0.669 0.872 ± 0.345 <0.001† 0.834 ± 0.356 <0.001† 0.736 ± 0.338 <0.001†
6 mm trefoil (μm) 1.066 ± 0.594 0.517 ± 0.318 <0.001† 0.462 ± 0.336 <0.001† 0.385 ± 0.279 <0.001†
6 mm coma (μm) 0.548 ± 0.280 0.346 ± 0.164 <0.001† 0.334 ± 0.171 <0.001† 0.301 ± 0.151 <0.001†
6 mm spherical (μm) 0.360 ± 0.261 0.249 ± 0.195 0.081 0.278 ± 0.162 0.123 0.281 ± 0.148 0.065

Values are presented as mean ± SD.

SD = standard deviation.

* Carried out using paired t-test (p < 0.05)

† Corneal total, trefoil and coma HOAs in the central 4 mm & 6 mm zone were statistically significantly decreased at 1 week, 1 month and 3 months after surgery in large group.

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