Posters

Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Binocular functions in anisometropic and strabismic anisometropic amblyopes

I. Akyol-Salman, Y. Karabela & O. Baykal

Ataturk University Faculty of Medicine, Department of Ophthalmology, Erzurum, Turkey

ABSTRACT: To evaluate binocular functions in anisometropic and strabismic anisometropic patients with amblyopia, 30 anisometropic and 25 strabismic anisometropic patients with amblyopia were included in the study. Synoptophore, Titmus and TNO tests were used for evaluation of binocular functions and stereoacuities. Spherical equivalent and Safir and Kulikowski’s root mean square formulae were used as an index of anisometropia. Correlation analysis, the test of significance between pairs, Wilcoxon rank analysis tests were used for statistical analysis. Subnormal binocularity was observed in all cases. Decrease in binocular functions was more in strabismic anisometropic amblyopes when compared with anisometropic amblyopes. As a conclusion, in amblyopic patients, impairment in binocular functions was augmented by the presence of strabismus, in addition to anisometropia.

1INTRODUCTION

Anisometropia and strabismus are the important causes of amblyopia. A strabismus frequently is associated with anisometropia, and to determine whether the amblyopia in an anisometropic strabismic patient is caused by the strabismus, the anisometropia, or both is difficult. As known, strabismic amblyopia is caused by active inhibition within the retinocortical pathways of visual input originating in the fovea of the deviating eye. This inhibition is the consequence rather than the cause of strabismus and is elicited by overlap of the different foveal images (confusion) transmitted to the visual centers from the retinas of the fixating eye and the deviating eye. As in the case of strabismic amblyopia, there is active inhibition of the fovea in anisometropic amblyopia; however, in the latter instance, the purpose of inhibition is to eliminate sensory interference caused by superimposition of a focused and a defocused image originating from the fixation point (abnormal binocular interaction). In spite of the similarities of the basic amblyopiogenic mechanisms, certain clinical differences exist between strabismic and anisometropic amblyopia in terms of severity, reversibility, and psychophysical characteristics (von noorden & campos 2002). In the present study we want to evaluate and compare the binocular functions in anisometropic and strabismic anisometropic patients with amblyopia.

2MATERIALS AND METHODS

30 Anisometropic (Mean ages 22.10 7.62 years) and 25 strabismic anisometropic patients (Mean ages 16.32 7.37 years) with amblyopia were included in the study. After a complete ophthalmologic examination, the following data were recorded and analyzed: unaided visual acuity, cycloplegic refraction, best-corrected Snellen visual acuity( logMAR), interocular acuity difference, interocular difference in refraction (by using two methods: the difference in spherical equivalents and the root mean square difference as defined by Safir & Kulikowski (1975), angle of the squint in strabismic anisometropic patients (PD), grade of binocular vision (by using synoptophore), and stereoacuity (by

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Table 1. Acuity, Refraction and Binocularity Data’s in the Groups.

using Titmus and TNO Tests). Table 1 summaries some of these data’s. Mean angle of deviations in strabismic anisometropic patients was 15.86 5.4 PD (19 ET, 6 XT). Of these patients 19 were anisohypermetropic and 6 were anisomyopic. In anisometropic patient group, 17 were anisohypermetropic and 13 were anisomyopic. The test of significance between pairs, correlation analysis, Wilcoxon rank analysis tests were used for statistical evaluation.

According to the statistical analysis of data’s between the groups: The significance was not observed on the, mean interocular acuity differences (P 0.564), mean interocular difference in refraction (the spherical equivalents) (P 0.362), and mean interocular difference in refraction (the root mean square) (P 0.163). The significance was observed on the mean stereoacuity with Titmus Test (P 0.000), mean stereoacuity with TNO Test (P 0.033), simultaneous perception (P 0.000), fusion (P 0.041), and stereopsis (P 0.041). According to the statistical analysis of data’s, strong correlation was found between: the type of amblyopia, the mean interocular acuity differences, the grades of binocular vision, the stereoacuity with Titmus test, the stereoacuity with TNO test (P 0.01), and the spherical equivalent index and the root mean square index (P 0.01).

In the present study:

•The degree of amblyopia was not correlated to the degree of anisometropia, for both anisometropic and strabismic anisometropic patients.

•The impairment in binocular functions increased with increasing degrees of amblyopia in both of the groups of anisometropic and strabismic anisometropic patients.

•Subnormal binocularity was found in all amblyopic patients.

•In spite of the similarities in the index of anisometropia of both groups, the degree of amblyopia was found to be more severe in strabismic anisometropic patients.

•In spite of the similarities in the index of anisometropia of both groups, impairment in binocular functions was found to be more in strabismic anisometropic patients.

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3CONCLUSION

In amblyopic patients, impairment in binocular functions was augmented by the presence of strabismus, in addition to anisometropia.

REFERENCES

Safir, A. & Kulikowski, C.A. 1975. Problems in the evaluation of data. Am Acad Ophthalmol. Otolaryngol: OP488: 79.

Von Noorden, G.K. & Campos, E.C. 2002. Binocular vision and ocular motility: Theory and management of strabismus. St. Louis: Mosby.

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