Fusional Vergence Dysfunctions in Acute Acquired Concomitant Esotropia of Adulthood with Myopia

Abstract

Introduction: Acute acquired concomitant esotropia (AACE) has been increased dramatically in myopia. To clarify whether fusional vergence dysfunctions exist in AACE with myopia, and to explore the relationship between fusional vergence and myopia in AACE Methods: A prospective clinical study. Adult AACE patients as well as controls (aged ≥18 years) both with myopia were prospectively recruited from October 2016 to August 2021. Refractive error and fusional divergence and convergence amplitude at distance were measured, as determined with a comprehensive refractor. The main outcome measures were the real value of the fusional divergence amplitude (calculated by subtracting the break point value from the angle of deviation) and the real value of the fusional convergence amplitude (calculated by subtracting the angle of deviation from the break point value). Two-sided p value of less than 0.05 was considered to indicate statistical significance. Results: Fusional vergence consisting of fusional divergence and fusional convergence in patients with AACE of adulthood were different from the controls (p<0.001), with fusional convergence decreased and fusional divergence increased. In the linear regression analysis, spherical equivalents were significantly negatively correlated with fusional convergence (right eyes, p<0.001; left eyes, p<0.001) in patients with AACE of adulthood but not in controls. There was a significant difference in fusional convergence amplitude among different degrees of spherical equivalents (p<0.001). Conclusions: Fusional vergence dysfunction exist in AACE of adulthood, which may be attributed to self-adaptation based on concomitant esotropia to maintain fusion in AACE. Fusional convergence was associated with degrees of myopia, implying the adaption would be weakened as the degree of myopia becomes serious.

Conformation of Horizontal Extraocular Muscle Insertions in Acute Acquired Concomitant Esotropia Induced by Excessive Digital Device Usage

“…A few studies revealed abnormal fusional amplitude in AACE patients with myopia. 30 , 31 However, it was reported that uncorrected myopia does not occur with AACE 30 onset. Although most of our patients in the SAACE group were myopic, as described above, there were no differences between either group for refraction error and axial length since all of the patients in the RD group were myopic.…”

Botulinum toxin type A in treating early-stage patients with small-angle acute acquired comitant esotropia

“…AACE, once considered a rare form of strabismus, has seen a significant rise in prevalence [18] . Despite its increasing occurrence, the etiology remains unknown, with potential factors including near work, accommodative convergence, fusion function, and physical and psychological stress [4,[19][20][21] .…”

Analysis of independent risk factors for acute acquired comitant esotropia

“…It is known that the ability of the eyes to fuse images is crucial for overcoming heterotropia. It is demonstrated that adult myopic patients with AACE exhibit impaired fusion divergence function, characterized by decreased fusion convergence and increased fusion divergence, serving as an adaptive mechanism to maintain fusion in the presence of heterotropia [18] . With increasing myopia, the adaptive capacity of fusion convergence diminishes.…”