The Changes of Corneal Astigmatism and Refraction After Horizontal Rectus Muscle Surgery in Intermittent Exotropia

Gui Hyeong Mun; Hwan Heo; Sang Woo Park; Yeoung Geol Park

doi:10.3341/jkos.2010.51.4.581

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Mun, Heo, Park, and Park: The Changes of Corneal Astigmatism and Refraction After Horizontal Rectus Muscle Surgery in Intermittent Exotropia

Original Article

J Korean Ophthalmol Soc 2010;51(4):581-587.

Published online: 25 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.4.581

The Changes of Corneal Astigmatism and Refraction After Horizontal Rectus Muscle Surgery in Intermittent Exotropia

Gui Hyeong Mun, MD, Hwan Heo, MD, Sang Woo Park, MD, Yeoung Geol Park, MD

Department of Ophthalmology, Chonnam National University Medical School and Hospital, Gwangju, Korea

Address reprint requests to Hwan Heo, MD Department of Ophthalmology, Chonnam National University Medical School and Hospital #8 Hak-dong, Dong-gu, Gwangju 501-757, Korea Tel: 82-62-220-6747, Fax: 82-62-227-1642, E-mail: opheye@hanmail.net

Received 9 July 2009 Accepted 22 December 2009

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 changes in corneal astigmatism and refractive power in intermittent exotropia after lateral rectus recession with or without medial rectus resection.

Methods

We compared visual acuity, spherical equivalent, refractive power, astigmatism from cycloplegic refraction, and Orbscan corneal topography in two groups consisting of 40 eyes from 20 patients who underwent bilateral lateral rectus recession (Group 1) and 33 eyes from 33 patients who underwent monocular medial rectus resection with lateral rectus recession (Group 2) immediately preoperatively and at 1 and 4 weeks postoperatively.

Results

In Group 1, the refractive power changed +0.12 D on average in the horizontal median and −0.08 D on average in the vertical median at 1 week postoperatively. The refractive power changed +0.07 D on average in the horizontal median and −0.04 D on average in the vertical median at 4 weeks postoperatively. No significant change in the corneal astigmatic axis was detected. In Group 2, the refractive power changed +0.4 D on average in the horizontal median and −0.19D on average in the vertical median, and the corneal astigmatic axis significantly shifted by +0.51 D in the ‘with-the-rule astigmatism’ direction at 1 week postoperatively (p=0.02). However, the refractive power changed +0.2 D on average in the horizontal median and −0.09 D on average in the vertical median, and the corneal astigmatic axis changed +0.2 D at 4 weeks postoperatively, although these values were not statistically significant.

Conclusions

Postoperative refractive power and corneal astigmatism did not change significantly, as compared to preoperative values, at 4 weeks postoperatively in the lateral rectus recession-only or medial-and-lateral rectus recession group.

Keywords: Corneal astigmatism, Lateral rectus recession, Medial rectus resection, Refractive power

References

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Figure 1.

Changes in mean corneal astigmatism using Orbscan at preoperatively and at 1 and 4 weeks postoperatively. (A) patients who underwent bilateral lateral rectus recession. (B) patients who underwent unilateral medial rectus resection with lateral rectus recession. ^* P<0.05, paired T test.

Figure 2.

Changes in mean horizontal and vertical refractive power at preoperatively and at 1 and 4 weeks postoperatively. (A) Patients who underwent bilateral lateral rectus recession. (B) patients who underwent unilateral medial rectus resection and lateral rectus recession. ^*P<0.05, paired T test. Preop.=preoperative; Postop.= postoperative.

Figure 3.

The graphs show a negative relationship in refractive power and corneal astigmatism change between preoperatively and 1 week postoperatively (A, C) and between 1 week and 4 weeks postoperatively (B, D) by Spearman correlation. Pre.=preoperative; Post.=postoperative.

Table 1.

Surgical guideline used in our study

Method		25PD^‡	30PD	35PD	40PD	45PD	50PD
BLR Rc^*	LR Rc (mm)	6	7	7.5	7	8	9
Unilateral R&R^†	MR Rs^§ (mm)	3	3	3.5	4	4.5	5
	LR Rc (mm)	5	6	6.5	7	7.5	8

^* Bilateral lateral rectus muscle recession

^† medial rectus muscle resection and lateral rectus muscle recession

^‡ prism diopter

^§ medial rectus resection.

Table 2.

Comparison of group 1 and group 2

	Group 1^*	Group 2^†	P-value^‡
Age (years, mean± SD^§)	7.8 ± 2.4 (6∼13)	8.7 ± 3.4 (5∼12)	0.65
Sex (men/women)	22/18	17/16
Laterality (OD/OS)	20/20	19/14
LogMAR visual acuity
BCVA^∏	0.05±0.97 (0.2∼0.0)	0.06±0.51 (0.2∼0.0)	0.74
UCVA^∏	0.12±0.64 (0.3∼0.0)	0.11±0.49 (0.3∼0.0)	0.81
Deviation angle (prism diopter, mean±	SD)
Near	33.7 ± 8.3 (25∼50)	36.1 ± 5.9 (25∼50)	0.61
Far	31.3± 7.9 (20∼45)	29.5 ± 8.6 (18∼50)	0.69
Spherical equivalent (mean± SD)	–1.12 ± 2.19	–1.29 ± 2.20	0.43
	(−4.25∼+2.0)	(−6.38∼+3.75)
Spherical	–0.78 ± 2.20	–0.75 ± 1.94	0.55
	(−5.25∼+3.5)	(−3.25∼+3.5)
Cylinder	–0.66 ± 0.48	–0.88 ± 1.48	0.21
	(−1.75∼+0.75)	(−3.5∼+1.0)

^* patients who underwent bilateral lateral rectus recession

^† patients who underwent unilateral medial rectus resection and lateral rectus recession

^‡ Mann-Whitney U test

^§ Standard deviation

^∏ Best corrected visual acuity

^＃ Uncorrected visual acuity.

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