A review of the classification of nonstrabismic binocular vision anomalies

Abstract

There are conflicting and confusing ideas in literature on the different types of accommoda- tive and vergence anomalies as different authors turn to classify them differently. This paper sought to review literature on the differ- ent 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 ver- gence dysfunctions using keywords like binoc- ular vision dysfunctions, classification of non- strabismic binocular vision disorders or anom- alies, accommodative disorders/anomalies clas- sification 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 accom- modative insufficiency, accommodative infa- cility (accommodative inertia), and accom- modative 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 insufficien- cy. Accommodative paralysis (subtype of accommodative insufficiency) and vergence anomalies – i.e., convergence paralysis, con- vergence spasm and divergence paralysis – are non-functional in origin with underlying sys- temic disease etiologies. Systemic conver- gence insufficiency, associated with subnor- mal accommodation, is a non-functional inter- action between the accommodative and con- vergence 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.