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Jung and Lee: The Ratio of Accommodative-Convergence to Accommodation in Patients with Intermittent Exotropia
Original Article
Journal of the Korean Ophthalmological Society

Journal of the Korean Ophthalmological Society 2012; 53(12): 1846-1850.

Published online: 17 December 2012

DOI: https://doi.org/10.3341/jkos.2012.53.12.1846

The Ratio of Accommodative-Convergence to Accommodation in Patients with Intermittent Exotropia

Jong Hyun Jung, MD, Se Youp Lee, MD

Department of Ophthalmology, Keimyung University Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea.

Address reprint requests to Se Youp Lee, MD. Department of Ophthalmology, Keimyung University Donsan Medical Center, #56 Dalseong-ro, Jung-gu, Daegu 700-712, Korea. Tel: 82-53-250-7720, Fax: 82-53-250-7707, lsy3379@dsmc.or.kr

Received 2 April 2012       Accepted 19 October 2012

Copyright © 2012 The Korean Ophthalmological Society

Abstract

Purpose

To measure the ratio of accommodative-convergence to accommodation (AC/A ratio) in patients with pseudodivergence excess type and convergence insufficiency type of intermittent exotropia [X(T)], and to compare with a normal group.

Methods

A total of 55 subjects were divided into 3 groups: pseudodivergence excess type, convergence insufficiency type, and normal group. Age, gender, and refractive error of patients were examined. The deviation angle was measured at near and distance by using a prism cover test, followed by an interpupillary distance measurement. The AC/A ratio was calculated using a heterophoria and a gradient method.

Results

There was no statistically significant difference in age, gender, and the refractive errors among the 3 groups. The mean value of AC/A ratio using the heterophoria method was 9.50 in pseudodivergence excess type patients, 2.59 in convergence insufficiency type patients, and 5.47 in the normal group. Using the gradient method, the mean value of AC/A ratio was 1.47, 0.03, and 2.08 in each group, respectively. There was no statistically significant difference in mean values between patients with pseudodivergence excess type and the normal group, except when obtained using the gradient method (p = 0.43).

Conclusions

A distinct difference in AC/A ratio existed when computed by the heterophoria method between patients with pseudodivergence excess type or convergence insufficiency type and the normal group. In the gradient method, however, the ratios of convergence insufficiency type patients were lower compared to the normal group, indicating the gradient method is more accurate than the heterophoria method.

Keywords: A ratio of accommodative-convergence to accommodation, Convergence insufficiency type, Intermittent exotropia, Pseudodivergence excess type

Figures and Tables

Table 1
Subject and subgroup demographics
jkos-53-1846-i001

Values are presented as mean ± SD.

SD = standard deviation; SE = spherical equivalent.

*Pseudo-divergence excess type; †Convergence insufficiency type; There was no statistically significant difference in gender distribution, mean age and the refractive error among the three groups.

Table 2
The average deviation after correction of refractive error
jkos-53-1846-i002

Values are presented as mean ± SD.

*Pseudo-divergence excess type; †Convergence insufficiency type; ‡Exodeviation; §Prism diopters.

Table 3
The average ratio of accommodative-convergence to accommodation of three groups
jkos-53-1846-i003

Values are presented as mean ± SD.

*Pseudo-divergence excess type; †Convergence insufficiency type; ‡Independent t-test using SPSS 12.0; §Comparison between group 1 and control; ∥Comparison between group 2 and control; #AC/A ratio was calculated using a heterophoria by prism diopter after patch.

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