Factors Influencing the Success of Treatment in Anisometropic Amblyopia

Amblyopia is a developmental disorder that degrades spatial vision and stereopsis. It is believed to follow abnormal binocular interaction or visual deprivation during early life and is the most common cause of visual morbidity in childhood.

A specific subtype, anisometropic amblyopia, develops when the image on the retina of one of the eyes is chronically de-focused caused by unequal refractive errors in both eyes.

Mild degrees of hyperopic or astigmatic anisometropia (1.00-2.00 D) can cause amblyopia, whereas higher levels of refractive error are usually required by myopic anisometropes to develop severe amblyopia.

Anisometropic amblyopia tends to be detected and consequently treated later than other forms of amblyopia as some children with anisometropia have no noticeable ocular misalignment. Consequently, these children may develop irreversible visual loss due to delayed diagnosis.

There is limited literature investigating visual outcomes for children with anisometropia in Canada.

The purpose of this study was to examine factors affecting final visual outcome following the treatment of children diagnosed with hyperopic and astigmatic anisometropia, presenting without apparent strabismus to a single surgeon’s pediatric ophthalmology practice in London, Ontario.

Factors Influencing the Success of Treatment in Anisometropic Amblyopia

A retrospective chart review was performed. The research protocol was approved by the Research Ethics Board of the University of Western Ontario. A computer search of the patient database of one pediatric ophthalmologist (IM) at the Ivey Eye Institute, University of Western Ontario, was performed to identify the records of all children ages 12 and under who presented with anisometropia upon referral from 2008-2016.

The following data were recorded: age at initial admission, a reason for presentation to referring doctor, present prescription and history of past management. We documented the presence of family history of amblyopia and/or strabismus, the presenting and final: visual acuity, cycloplegic refraction, and ocular alignment. We also documented compliance with treatment and final sensory testing including worth 4-dot test for distance and near as well as stereo acuity.

Data from the 39 patients who had adequate follow-up was used for statistical analysis and to determine baseline characteristics. No significant correlation was found between presenting the degree of anisometropia and presenting visual acuity.

17 (44%) children were found to have residual mild amblyopia worse than 6/9 but better than 6/30 at their final follow-up visit. All but one of the 17 children were older than 4 years at presentation, 6 (35%) presented with a magnitude of anisometropia of ≤ 3.00 D, 10 (59%) had presented with dense amblyopia at their first visit and 4 (24%) were noted to have poor compliance with the offered treatment.

2 children (5%) had residual dense amblyopia at their final follow-up visit, both children initially presented above the age of 7, presented with a magnitude of anisometropia > 3.00 D and were noted to have poor compliance with the offered treatment. These 2 children had no evidence of fusion or stereopsis at their final visit.

At the final visit, 7 (17.9%) children showed a stereopsis of 60 seconds of arc or better and 9 (23.1%) had no evidence of stereopsis. Of these 9 children, 8 presented above the age of 4 years and presented with dense amblyopia. Following treatment, 6 of these 9 children had residual mild amblyopia and 3 children had residual dense amblyopia.

The results from this study demonstrate that magnitude of anisometropia has a significant influence on the final visual acuity of children diagnosed with hyperopic and astigmatic anisometropia, while presenting age, presenting visual acuity, and compliance to treatment regimen do not.

This article first published in International Journal of Ophthalmology & Eye Science (IJOES) by SciDoc Publishers.

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