A review of the classification of nonstrabismic binocular vision anomalies

Abstract

There are conflicting and confusing ideas in literature on the different types of accommodative and vergence anomalies as different authors turn to classify them differently. This paper sought to review literature on the different classifications and types of nonstrabismic binocular vision anomalies and harmonize these classifications. Search engines, namely Google scholar, Medline, Cinahl and Francis databases, were used to review literature on the classification of accommodative and vergence dysfunctions using keywords like binocular vision dysfunctions, classification of nonstrabismic binocular vision disorders or anomalies, accommodative disorders/anomalies classification and vergence disorders/anomalies classifications, and included works that described these anomalies. Nonstrabismic binocular vision anomalies are classified as accommodative and vergence anomalies. There are three different major types of accommodative anomalies, namely accommodative insufficiency, accommodative infacility (accommodative inertia), and accommodative excess (accommodative spasm), and seven different types of vergence anomalies (convergence insufficiency, convergence excess, divergence insufficiency, divergence excess, basic esophoria, basic exophoria and fusional vergence dysfunctions), which are functional in origin. Functionally, there is a commonly reported interaction between accommodative and convergence insufficiency referred to as pseudoconvergence insufficiency. Accommodative paralysis (subtype of accommodative insufficiency) and vergence anomalies -i.e., convergence paralysis, convergence spasm and divergence paralysis -are non-functional in origin with underlying systemic disease etiologies. Systemic convergence insufficiency, associated with subnormal accommodation, is a non-functional interaction between the accommodative and convergence insufficiency. The classification of nonstrabismic binocular vision anomalies is based on the description of the clinical signs and the underlying etiology either functional or non-functional in origin. Proper diagnosis and management involves investigation of the underlying etiology in addition to the battery of binocular vision test procedures.

Quantitative Evaluation of the Association Between Fixation Stability and Phoria During Short-Term Binocular Viewing

“…In the abnormal group, the direct and indirect relationships with BCEA are presumed to mean that several factors are involved in maintaining binocular vision due to the instability of the binocular system. Such an interpretation can be found in the characteristics (including reduced convergence and near deviation) in the abnormal phoria group consisting of convergence insufficiency, convergence excess, basic exophoria, and basic esophoria (Blum et al, 2015;Darko-Takyi et al, 2016;Yu et al, 2018). These vergence fluctuations may therefore lead to a reduction in binocular fixation stability.…”

“…To maintain binocular vision, individuals with abnormal phoria must use vergence ( Darko-Takyi et al, 2016 ). Therefore, we expected that eye movements would continuously occur during binocular viewing, which would eventually affect the fixation stability.…”

“…The participants included 35 university students with abnormal phoria and 25 with normal phoria. Types of the abnormal phoria group were classified based on phoria and the calculated AC/A (accommodative convergence to accommodation ratio) according to Scheiman and Wick’s study ( Darko-Takyi et al, 2016 ).…”

Receiver operating characteristic curve analysis of clinical signs for screening of convergence insufficiency in young adults

“…All these previous studies have evaluated the validity of diagnostic tests between symptomatic patients with CI and normal participants. However, in addition to cases of independent CI, CI can present with signs associated with other vergence disorders or accommodative disorders in clinical diagnoses of non-strabismic binocular vision anomalies [13]. The symptoms of CI are common in adults, but they often do not appear [1,5].…”

“…In the final approach, however, the symptoms may not be related to clinical signs, especially in adults. Many symptomatic CI disorders are related to the presence of defects in two or more areas of binocular vision function [13,14].…”