J Korean Ophthalmol Soc.  2012 Dec;53(12):1846-1850. 10.3341/jkos.2012.53.12.1846.

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

• Jung JH
• Lee SY

• KMID: 2216400
• DOI: http://doi.org/10.3341/jkos.2012.53.12.1846

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.

Keyword

A ratio of accommodative-convergence to accommodation; Convergence insufficiency type; Intermittent exotropia; Pseudodivergence excess type

MeSH Terms

Exotropia
Humans
Ocular Motility Disorders
Refractive Errors

Reference

1. Jin YH. Strabismology. 1999. 2nd ed. Ulsan: Ulsan University press;181–183.

2. Duane A. A new classification of the motor anomalies of the eye: based upon physiologicals principle, together with their symptoms, diagnosis and treatment. Ann Ophthalmol Otolaryngol. 1896. 5:969.

3. Fry GA, Haines HF. Taits' analysis of the accommodative-convergence relationship. Am J Optom. 1940. 17:393–397.

4. Fry GA. Further experiments on the accommodation convergence relationship. Am J Optom. 1939. 16:125–129.

5. Wright KW. Wright KW, editor. Motor aspect of strabismus. Textbook of Ophthalmology. 1997. 1st ed. Baltimore: Williams & Wilkins;233–253.

6. Eskridge JB. Age and the ac-A ratio. Am J Optom Arch Am Acad Optom. 1973. 50:105–107.

7. Von Noorden GK, Campos EC. Binocular vision and ocular motility : theory and management of strabismus. c2002. 6th ed. St. Louis: CV Mosby;92.

8. Anson AM, Davis H. Diagnosis and management of ocular motility disorders. 2001. 3rd ed. London: Blackwell Science;93.

9. Lee SY. Comparison of the AC/A ratio by the grdient method and the heterophoric method in normal subjects. J Korean Ophthalmol Soc. 2000. 41:1790–1795.

10. Franceschetti AT, Burian HM. Gradient accommodative convergence-accommodative ratio in families with and without esotropia. Am J Ophthalmol. 1970. 70:558–562.

11. Wright KW, Spiegel PH. Exotropia. Pediatric Ophthalmology and Strabismus. 2003. 2nd ed. New York: Springer;chap. 14.

12. Kushner BJ. Exotropic deviations: A functional classification and approach to treatment. Am Orthoptic J. 1988. 38:81–93.

13. Brown HW. Aids in the diagnosis of strabismus. Strabismus. Symposium of the New Orleans Academy of Ophthalmology. 1962. St Louis: Mosby-year Book;231.

14. Rutstein RP, Daum KM. Anomalies of binocular vision : diagnosis & management. c1998. 1st ed. St. Louis: Mosby;260–261.