Sir,

We thank JJ Jiang and Q Wu for their interest in our study. They focus on the possible association of large overcorrection with poor prognosis and the prism’s influence on visual acuity and amblyopia development.

For patients with persistent esodeviation months after occlusion therapy (average: 4.6 months, range: 0.5–12.0 months), we prescribed Fresnel prism, sometimes later changing to regular spectacles with prism(s). The average prism usage was 9.5 months (range: 1.5–24.0 months); at final follow-up, no patient still required it. We do not believe that large-angle overcorrection is associated with poor long-term ocular alignment: our four patients with immediate post-operative esodeviation≥20 PD achieved ocular alignment within 6 PD of orthotropia by 1-year follow-up. As for accommodation, most of our subjects had myopia, not hyperopia. Fourteen eyes of 10 patients (6.7%) out of 149 of this patient group had preoperative spherical equivalent of ≥+1.0 D. Among them, only one had immediate postoperative esodeviation over 20 PD, who became exotropic 3 weeks postoperatively with alternative occlusion therapy. There was one patient with small esophoria at distance and a larger esotropia at near; he was prescribed bifocal spectacles at 2 months follow-up, later showing orthotropia at 7 months follow-up without amblyopia development. Hwang et al1 reported long-term conservative management outcomes for 68 patients with 20 PD or more initial overcorrection following exotropia surgery. They determined that in most patients, overcorrection had been reduced to 10 PD or less (distance and near) within 4 weeks.

Visual acuity reduction can be induced by Wafer prisms, Fresnel trial set prisms, and conventional prisms; however, the effect is negligible with prism powers <12 PD.2 All of the prisms we used had powers of ≤12 PD, and we believe that there was no substantial visual acuity deterioration or, therefore, any significant potential for prism-related amblyopia development. At the final follow-up, among the 19 patients who had preoperative amblyopia, none demonstrated a BCVA below 20/30. Neither was there any case of new-onset amblyopia. Hwang and Lee,3 correspondingly, reported no cases of new-onset amblyopia among 110 consecutive esotropia patients managed with prismatic correction.