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Adaptive disorders of accommodation and vergence in binocular dysfunction
Author(s) -
Schor Clifton,
Horner Douglas
Publication year - 1989
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/j.1475-1313.1989.tb00904.x
Subject(s) - accommodation , tonic (physiology) , vergence (optics) , convergence insufficiency , binocular vision , adaptation (eye) , psychology , convergence (economics) , audiology , optometry , medicine , computer science , neuroscience , ophthalmology , artificial intelligence , economics , economic growth
Disturbances of binocular vision are described clinically by the Duane‐White classification in terms of the magnitude of the accommodative‐convergence ratio (AC/A). Convergence excess and convergence insufficiency are assumed to result from high and low AC/A ratios respectively. It is assumed that the abnormal AC/A ratio is an independent variable that underlies abnormal phorias. However, recent studies have demonstrated that the AC/A ratio is inversely related to the adaptability of tonic accommodation (lens adaptation) and directly related to adaptability of tonic vergence (prism adaptation). We have tested whether clinical categories of convergence excess and convergence insufficiency are associated with insufficient and excessive adaptation of tonic accommodation and tonic vergence. Results demonstrate greater amplitude and duration of accommodative after‐effects (lens adaptation) in the convergence insufficiency than the convergence excess group. Vergence after‐effects (prism adaptation) had the reverse trend for the two groups. These results indicate that adaptive disorders of accommodation and vergence may underlie binocular disorders in symptomatic patients categorized as convergence excess and convergence insufficiency.