The Meaning of Monocular Occlusion on Preoperative Evaluation in Basic Intermittent Exotropia

Sun Young Jang; Ja Young Lee; Song Hee Park; So Young Kim

doi:10.3341/jkos.2009.50.9.1371

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Jang, Lee, Park, and Kim: The Meaning of Monocular Occlusion on Preoperative Evaluation in Basic Intermittent Exotropia

Original Article

J Korean Ophthalmol Soc 2009;50(9):1371-1376.

Published online: 7 September 2009

DOI: https://doi.org/10.3341/jkos.2009.50.9.1371

The Meaning of Monocular Occlusion on Preoperative Evaluation in Basic Intermittent Exotropia

Sun Young Jang, MD^1,², Ja Young Lee, MD^1,³, Song Hee Park, MD^1,², So Young Kim, MD^1,³

¹Department of Ophthalmology, Soonchunhyang University College of Medicine, Seoul, Korea

²Department of Ophthalmology, Soonchunhyang University Hospital, Seoul, Korea

³Department of Ophthalmology, Soonchunhyang University Cheonan Hospital, Cheonan, Korea

Address reprint requests to So Young Kim, MD Department of Ophthalmology, College of Medicine, Soonchunhyang University #23-20 Bongmyeong-dong, Cheonan 330-721, Korea Tel: 82-41-570-2933, Fax: 82-41-576-2262, E-mail: ophdrkim@schch.co.kr

Received 28 October 2008 Accepted 1 September 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 assess the clinical potential of one hour monocular occlusion on preoperative alignment evaluation in basic intermittent exotropia.

Methods

Twenty-nine patients with basic intermittent exotropia who were preoperatively examined for one hour monocular occlusion were selected (monocular occlusion group). Their records were reviewed retrospectively. The measured angle after one hour of monocular occlusion was used to determine the surgical target angle. The control group consisted of 29 patients whose age, sex and control state were similar to the monocular occlusion group. Measurement of the angle of strabismus was not done in the control group. Surgery was performed for the measured angle at six meters. The results of surgery were used to compare the groups relative to the control state.

Results

Fifteen patients (51.7%) had an increase in the distance deviation after one hour of monocular occlusion. Of the patients with good control, 78.6% (11/14) had an increase in the angle of misalignment. Only 26.7% (4/15) of patients with poor control experienced a change in the angle deviation (p<0.05). In all, 79.3% of patients in the study group and 75.9% of those in the control group had a satisfactory surgical outcome. Among the patients with good control, 85.7% of patients who underwent surgery for increased angle had a satisfactory outcome, compared with 71.4% of patients who underwent surgery for initial angle (p=0.375).

Conclusions

One-hour monocular occlusion might help to prevent undercorrection after surgical treatment by identifying the hidden deviation, especially in the patients whose control over the distance deviation was good.

Keywords: Basic type, Fusion, Intermittent exotropia, Monocular occlusion

References

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Table 1.

Characteristics of study group^∗ and control group

	Study group^∗	Control group
Number of patients	29	29
Age of patients (Mean± SD^†, months)	82.34±37.96	86.97±28.74
Male/Female (Percentage ratio)	16/13 (55.2/44.8)	17/12 (58.6/41.4)
Pre‐occlusion deviation angle (Mean± SD^†, PD^‡)	27.28±6.24	28.39±5.70
Follow up duration (Months)	7.17±1.73	8.53±1.82
Age at surgery (Mean± SD^†, months)	91.66±31.12	93.45±32.70

^∗ Study group=the patient group in whom the angle of deviation was preoperatively measured after 1-hour monocular occlusion (patch test);

^† SD=standard deviation;

^‡ PD=prism diopter.

Table 2.

The pre-occlusion and post-occlusion deviating angle in study group

	Responder^∗	Non responder
Pre-occlusion deviation angle	24.73±6.76	26.79±4.21
Post-occlusion deviation angle	30.14±6.50	27.07±4.14
p-value	<0.001	0.158

(p-value was calculated by Paired t-test)

^∗ Responder=angle of misalignment was increased in 5 PD or more after 1 hour of monocular occlusion; Non responder=angle of misalignment was not increased after 1 hour of monocular occlusion.

Table 3.

Comparison of response between two groups with respect to control state in patients with 1-hour monocula occlusion.

	Responder^∗	Non responder
Number of patient with good control	11 (78.6%)	3 (21.4%)
Number of patient with poor control	4 (26.7%)	11 (73.3%)

(p-value=0.005, calculated by Chi‐square test and Fisher exact test)

^∗ Responder=angle of misalignment was increased in 5PD or more after 1 hour of monocular occlusion; Non responder=angle of misalignment was not increased after 1 hour of monocular occlusion.

Table 4.

Results of surgery by subsets of patients with control status

	Success rate of surgery (Number of patient)		p-value^∗
	Study group^† (n=29)	Control group (n=29)	p-value^∗
Patients with good and poor control	79.3% (23/29)	75.9% (22/29)	0.753
Patients with good control only	85.7% (12/14)	71.4% (10/14)	0.357

^∗ p-value was calculated by Chi‐square test;

^† Study group=The patient group in whom the angle of deviation was preoperatively measured 1 hour after monocular occlusion.

Table 5.

The pre‐operative and postoperative deviating angle in study group

Postop deviation angle	Study group^† (n=29)	Control group (n=29)	p-value^∗
Patients with good and poor control	2.03±6.17	3.62±3.97	0.166
Patients with good control only	1.57±5.56	3.21±3.89	0.477

^∗ p-value was calculated by Paired t-test;

^† Study group: The patient group in whom the angle of deviation was preoperatively measured 1 hour after monocular occlusion.

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