Short-term outcomes of prism treatment in a manner of reducing prism diopters step by step for small-angle acute acquired concomitant esotropia

Abstract

Objective: To investigate the short-term efficacy of the prism treatment in a manner of reducing prism diopters step by step for small-angle acute acquired concomitant esotropia (AACE). Methods: Retrospective case series study. The clinical data of 17 AACE patients with strabismus ≤25 prism degrees (PD) including 6 males and 11 females, aged 14 to 60 years, who underwent the prism treatment in the Strabismus and Pediatric Ophthalmology Clinic of Shanxi Eye Hospital from October 2018 to June 2020 were collected. The prism treatment was conducted by a step-by-step reduction of prism diopters. An under-corrected prism was applied to the patient for the first time, and the degree of the prism was reduced gradually with the decrease in the degree of strabismus. Statistical analysis was performed after 6 months of treatment. The treatment success was defined as obtaining orthotropia and deleting diplopia when prism glasses were weaned off. The strabismus degree, Worth 4 dot test results, near stereopsis (Titmus stereopsis) and synoptophore fusion function before and after treatment were compared, and the factors affecting the curative effect were analyzed. Statistical methods mainly included paired t-test, Wilcoxon rank sum test, the Fisher exact test and univariate logistic regression analysis. Results: Among these 17 patients, 15 had myopia and 2 had emmetropia. Pretherapeutic esodeviation was (13.94±5.83) PD at near (33 cm), and was (15.76±5.24) PD at distance (6 m). After 6 months of treatment, 7 patients were successfully cured. The deviation angle at distance [(10.60±7.16) PD] and near [(9.80±6.00) PD] of the remaining 10 patients at 6 months after prismatic treatment was significantly smaller than that before treatment [(17.50±5.40) PD and (16.10±5.47) PD; t=3.69, 4.10; both P<0.01]. The Titmus stereogram showed that 2 cases had no stereopsis, 6 cases had peripheral stereopsis, 3 cases had macular stereopsis, and 6 cases had foveal stereopsis before treatment. Stereopsis was significantly improved at 6 months after prismatic treatment, with 3 cases havimg macular stereopsis and 14 cases having foveal stereopsis (Z=-2.99; P<0.01). The Worth-4-dot test disclosed that, the number of patients who saw four lamps at distance and near was 0 and 2 before treatment, and 7 and 9 after treatment, respectively, and the difference was statistically significant (both P<0.05). The divergent fusional amplitude and convergent fusional amplitude in the synoptophore at 6 month after treatment was not significantly different from that before treatment (both P>0.05). The efficacy of treatment was not significantly related to the duration from onset to treatment, the pretherapeutic esodeviation, the Titmus stereoacuity, cycloplegic refractive error, and age (all P>0.05). None of the 7 patients, who were successfully cured had a recurrence of esotropia or diplopia during the observation period of 6 to 24 months (median, 11 months). Conclusions: Prism treatment in a manner of step-by-step reduction of prism diopters can significantly diminish the degree of esotropia and improve the binocular function in small-angle AACE. Furthermore, some patients could be cured, achieving orthophoria without diplopia.