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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: According to the results of this study, treatment of IXT by over-correcting lenses can be a safe procedure and effective in preventing exotropia.