Role of Overcorrecting Minus Lens Therapy in Intermittent Exotropia for Prevention of Constant Exotropia in Children Under the Age of 7 Years

The basis of the overcorrecting minus lens is to induce compliance and consequently prevent constant exotropia. Some previous studies advocated early surgical therapy and others suggested over‑minus treatment. Our purpose is to evaluate the success rate of the over‑minus lens.

This descriptive cross‑sectional study was carried out on 106 patients under the age of 7 years with intermittent exotropia (IXT) who attended Amir‑Al‑Momenin Hospital at Guilan University of Medical Sciences, Iran. The data was gathered by a form including sex, age, level of cycloplegic refraction, the amount of deviation before and after using the over‑minus glasses, visual acuity, the amount of the over‑minus glasses, duration of treatment, recovery, and follow‑up. The success rate was defined as decreasing exotropia to less than ten prism diopters or exophoria.

A total of 106 patients with a mean age of 2.25 ± 0.74 years were enrolled in this study. The mean exotropia before and after treatment was 20.96 ± 8.20 and 12.16 ± 11.04 prism diopters, respectively, and there was a statistically significant difference (P < 0.002). The mean refractive spherical and astigmatic errors (cycloplegic refraction) were +1.34 ± 1.07 and −0.32 ± 0.72 diopters, respectively. At the end of the follow‑up, exotropia increased in 5.6% of patients, there was no change in 15% of patients with a mean deviation of 25.0 ± 6.06 prism diopters, and 79.24% of patients were treated successfully.

According to the results of this study, treatment of IXT by over‑correcting lenses can be a safe procedure and effective in preventing exotropia.