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Lee, Lee, Lee, Oh, Lee, and Kwon: The Accuracy of Estimating Postoperative Deviation in Exotropia With over 40 Prism Diopters
Original Article

J Korean Ophthalmol Soc 2010;51(12):1614-1619.

Published online: 7 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.12.1614

The Accuracy of Estimating Postoperative Deviation in Exotropia With over 40 Prism Diopters

Byeong Hee Lee, MD1, Jong Wook Lee, MD1, Jung Ho Lee, MD1, Dong Ryeul Oh, MD2, Kyoo Won Lee, MD1, Jung Yoon Kwon, MD1

1Cheil Eye Hospital, Daegu, Korea

2Lim&Oh Eye Clinic, Daegu, Korea

Address reprint requests to Jung Ho Lee, MD Cheil Eye Hospital #803-2 Sinam-dong, Dong-gu, Daegu 701-011, Korea Tel: 82-53-959-1751, Fax: 82-53-959-1758, E-mail: eyejholee@hanmail.net

Received 13 April 2010       Accepted 23 November 2010

Copyright © 2010 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 assess the accuracy of estimating postoperative deviation in large-angle exotropia over 40 prism diopters (PD).

Methods

A retrospective analysis was performed on 61 exotropia patients with over 40 PD exotropia who had undergone 2-muscle surgery by two surgeons and with at least 6 months follow-up. The accuracy was assessed by analyzing the discrepancy between preoperatively predicted residual deviation and deviation at postoperative 6weeks. Successful surgery was defined as deviation within ± 10 PD at the last postoperative visit.

Results

More accurate residual deviation was predicted in exotropia with prism diopters between 40 and 59 (97.8%) than in exotropia with 60 PD or more (62.5%). And there was no significant difference between two surgeons. Surgical success rates at six months and one year after surgery were 96.8%, 94.7% in exotropia with 40 to 49 PD, 71.4%, 60.0%, 50 to 59 PD, 50.0%, 45.5%, 60 PD or more, respectively. There were four patients of whom the postoperative deviation angle ex-ceeded more than 10 PD of the estimated deviation.

Conclusions

The accuracy of estimating residual deviation prior to surgery was higher and more successful surgery was achieved in exotropia ranging in 40 to 59 PD than in exotropia with 60 PD or more. Therefore, 2-muscle surgery will be suitable for large-angle exotropia with less than 60 PD.

Keywords: Large-angle exotropia

References

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Figure 1.
Scatter diagram of difference between estimated residual deviation and actual residual deviation.
jkos-51-1614f1.tif
Table 1.
Surgical guidelines
Deviation (PD*) Bilateral recession of lateral rectus Unilateral recession of lateral rectus/ resection of medial rectus Bilateral resection of medial rectus
40PD 8.0∼8.5 mm 8.0∼8.5 mm/5.0∼5.5 mm 5.5 mm
45PD 9.0 mm 8.5∼9.0 mm/5.5∼6.0 mm ⋅
50PD ⋅ 9.0 mm/5.5∼6.0 mm 6.0 mm
55PD ⋅ 8.5∼9.5 mm/6.0 mm ⋅
> 60PD ⋅ 9.0∼10.0 mm/6.0∼6.5mm 6.0 mm

* PD=Prism diopters.

Table 2.
Demographics of patients with large angle exotropia
Oh† Lee† Total
Number of patients 37 24 61
Age (year) (range) 29.9 ± 16.3 (3–62) 38.3 ± 3.4 (7–74) 33.2 ± 16.8 (3∼74)
Sex (male/female) 17/20 13/11 30/31
Preoperative deviation (PD*, Mean±SD) 49.1 ± 10.6 (40–78) 56.2 ± 15.2 (40–94) 51.9 ± 13.0 (40∼94)
Corrected deviation (PD*, Mean±SD) 46.8 ± 9.5 (30–72) 51.6 ± 10.2 (40–84) 48.7 ± 10.0 (30∼84)
Follow-up (months) 17.8 ± 13.5 (6–48) 8.8 ± 5.2 (6–30) 14.3 ± 11.8 (6∼48)

* PD = Prism diopters

† Oh, Lee = Operator.

Table 3.
Discrepancy between preoperatively estimated residual deviation and residual deviation at postoperative 6 weeks in exotropiaexperimental with over 40PD
Preoperative deviation Operator Number of patients Amount of deviation to correct (PD*) Discrepancy between estimated residual and postoperative deviations No. (%)
within ±10PD Overcorrected‡ Undercorrected§
40 Oh† Lee† 134 40 13 (100) 4 (100) 0 (0) 0 (0) 0 (0) 0 (0)
45 Oh Lee 10 4 45 10 (100) 4 (100) 0 (0) 0 (0) 0 (0) 0 (0)
50 Oh Lee 3 6 50 2 (66.7) 6 (100) 0 (0) 0 (0) 1 (33.3) 0 (0)
55 Oh Lee 3 2 50 or 60 3 (100) 2 (100) 0 (0) 0 (0) 0 (0) 0 (0)
≥ 60 Oh Lee 8 8 50 or 55 or 60 5 (62.5) 5 (62.5) 2 (25.0) 2 (25.0) 1 (12.5) 1 (12.5)

* PD = Prism diopters

† Oh, Lee = Operator

‡ Overcorrected = >10PD overcorrected than estimated residual deviation

§ Undercorrected = >10PD undercorrected than estimated residual deviation; No significant difference between two surgeons (p = 0.84, Chi-square test).

Table 4.
Surgical results according to the deviation angles at postoperative 6weeks, 6months and 1year
Preoperative deviation Success rate No. (%)
Postoperative 6weeks Postoperative 6months Postoperative 1year
40∼49PD* 30/31 (96.8) 30/31 (96.8) 18/19 (94.7)
50∼59PD 12/14 (85.7) 10/14 (71.4) 6/10 (60.0)
≥60PD 7/16 (43.8) 8/16 (50.0) 5/11 (45.5)
Total 49/61 (80.3) 48/61 (78.7) 29/40 (72.5)

* PD = Prism diopters.

Table 5.
Surgical success rates at postoperative last visit according to the preoperative deviations
Preoperative Deviation (PD*) Operator Number of patients Number of patients according to the surgical results (%)
Corrected‡ Overcorrected§ UndercorrectedΠ
40∼49 Oh† 23 22 (95.7) 0 (0) 1 (4.3)
Lee† 8 8 (100) 0 (0) 0 (0)
50∼59 Oh 6 4 (66.7) 0 (0) 2 (33.3)
Lee 8 6 (75.0) 0 (0) 2 (25.0)
≥60 Oh 8 3 (37.5) 0 (0) 5 (62.5)
Lee 8 5 (62.5) 0 (0) 3 (37.5)

* PD=Prism diopters

† Oh, Lee =Operator

‡ Corrected =within 10PD or orthotropia

§ Overcorrected =>10PD of esotropia

Π Undercorrected = >10PD of exotropia

No significant difference between two surgeons (p = 0.82, Chi-square test).

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