The Association Between Amblyopia and Anisometropia in Intermittent Exotropia

Myun Ku; Hae Jung Paik

doi:10.3341/jkos.2009.50.11.1686

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Ku and Paik: The Association Between Amblyopia and Anisometropia in Intermittent Exotropia

Original Article

J Korean Ophthalmol Soc 2009;50(11):1686-1691.

Published online: 31 August 2009

DOI: https://doi.org/10.3341/jkos.2009.50.11.1686

The Association Between Amblyopia and Anisometropia in Intermittent Exotropia

Myun Ku, MD, Hae Jung Paik, MD, PhD

Department of Ophthalmology, Gachon University Gil Medical Center, Incheon, Korea

Address reprint requests to Hae Jung Paik, MD, PhD, Department of Ophthalmology, Gachon University Gil Medical Center #1198 Guwol-dong, Namdong-gu, Incheon 405-760, Korea Tel: 82-32-460-3364, Fax: 82-32-460-3358, E-mail: hjpaik@gilhospital.com

Received 3 November 2009 Accepted 28 July 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 determine the frequency of amblyopia and anisometropia in intermittent exotropia and to evaluate the relationship between anisometropia and amblyopia.

Methods

The medical records of 471 intermittent extotropia patients, who were followed up over a period of 6 months and ranged from 3 to 15 years of age had been retrospectively reviewed. Anisometropia patients, who had either spherical or cylindrical anisometropia of more than 1.00D, were divided into 4 groups: spherical hyperopic anisometropia (SHA), spherical myopic anisometropia (SMA), cylindrical hyperopic anisometropia (CHA), and cylindrical myopic aniometropia (CMA).

Results

The frequency of amblyopia in the intermittent exotropia group was 41/471 (8.7%). Amblyopia results in a significant increase in the incidence of anisometropia and a decrease in binocular function when compared with non-amblyopic patients. In the amblyopia group, 14 patients had anisometropia (34.1%) consisting of 2 patients with spherical myopic anisometropia (SMA), 2 patients with spherical hyperopic anisometropia (SHA), 2 patients with cylindrical myopic anisometropia (CMA) and 8 patients with cylindrical hyperopic anisometropia (CHA). In the anisometropia group (n=56) 14 patients (25.0%) had amblyopia and in the non‐ anisometropia group (n= 415) 27 patients (6.5%) had amblyopia.

Conclusions

Intermittent exotropia is susceptible to amblyopia, especially when combined with anisometropia. Among the 4 types of anisometropia, cylindrical hyperopic anisometropia has a higher risk for developing amblyopia.

Keywords: Amblyopia, Anisometropia, Intermittent exotropia

References

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Figure 1.

Percentage of each type of anisometropia in the amblyopia patients. MSA=myopic spherical anisometropia; HAS=hyperopic spherical anisometropia; MCA=myopic cylindrical anisometropia; HCA=hyperopic cylindrical anisometropia.

Table 1.

Clinical characteristics of amblyopia and non-amblyopia group

	Amblyopia (n=41)	Non‐amblyopia (n=430)	p-value
Gender (Male:Female)	21:20	199:231	0.624^*
Age (Yr)
Diagnosis	6.17±3.05	6.50±2.71	0.462^†
Onset	3.90±2.60	4.45±2.42	0.173^†
Deviation angle (PD)
Near	26.93±6.98	26.56±7.55	0.763^†
Distance	27.73±5.95	27.54±6.07	0.845^†

^*Pearson chi-square test

^†Independent t-test

PD=prism diopter.

Table 2.

Anisometropia and stereoacuity data in amblyopia and non-amblyopia group

	Amblyopia (n=41)	Non‐amblyopia (n=430)	p-value
No. (%) of anisometropia^† eyes	14 (34.1%)	42 (9.8%)	0.000^*
No. (%) of stereoacuity^‡ >100sec/arc	17 (41.5%)	90 (20.9%)	0.003^*

^*Pearson chi-square test

^†Anisometropia was defined as ≥1.00D difference in spherical or cylindrical refractive error between eyes

^‡Stereoacuity was measured using the Titmus stereo test (Stereo Optical Co., Inc., Chicago, IL).

Table 3.

Number of patients, degree of anisometropia, frequency of amblyopia according to the type of anisometropia

	SA^*			CA^†			Total
	MSA^‡	HSA^§	Total	MCA^∏	HCA^＃	Total	Total
Patient No. (%)	15(26.8%)	(19.6%)11	26 (46.4%)	(16.1%)9	(37.5%)21	30(53.6%)	56(100%)
Degree of	‐1.80	1.50	1.67	1.44	1.43	1.43
anisometropia (D)
No. of amblyopic	2	2	4	2	8	10	14
eyes (%)	(13.3%)	(18.2%)	(15.4%)	(22.2%)	(38.1%)	(33.3%)	(25.0%)

^*SA=spherical anisometropia

^†CA=cylindrical anisometropia

^‡MSA=myopic spherical anisometropia

^§HAS=hyperopic spherical anisometropia

^∏MCA=myopic cylindrical anisometropia

^＃HCA=hyperopic cylindrical anisometropia.

Table 4.

Degree of spherical anisometropia according to the type of anisometropia

	SA^* (n=4)		CA^† (n=10)
	MSA^‡ (n=2)	HAS^§ (n=2)	MCA^∏ (n=2)	HCA^＃ (n=8)
Mean degree of Spherical anisometropia (D)	−3.50	2.88	−1.75	0.44