The roles played by the accommodationconvergence synkinesis and by the proximal influences in the total convergence of the eyes required for a given viewing distance may be factors to be considered clinically. They may be important in the prescribing of refractive corrections, in the understanding of asthenopic symptoms from heterophorias, and in the more general problem of accommodative strabismus.
Asher1 expressed the belief that the subject's conscious estimate of the position of an object plays as important a role as does the accommodative convergence. Furthermore, he found evidence that the proximal factor predominates in patients with asthenopia and also affects the results obtained in accommodative squint with positive lenses. In a similar vein, Guzzinati2 found that the proximity factor affects and often determines convergence and, particularly, is reduced nearly one-half in persons showing a convergence insufficiency.
The two common methods for estimating the change in convergence due to