The Development of Convergence and Accommodation

Horwood,A Riddell,P.. British & Irish Orthoptic Journal 2004; 1, 1

• A review of the literature of convergence and accommodation development

Aim

To review current literature on the development of convergence and accommodation. The accommodation and vergence systems provide the foundation upon which bifoveal binocular single vision develops. Deviations from their normal development are implicated in the aetiology of not only convergence anomalies, accommodative anomalies and strabismus, but may also be implicated in failure of the emmetropisation process.

Methods

This review considers the problems of researching the development of accommodation and vergence in infants and how infant research has had to differ from adult methods. It then reviews and discusses the implications of current research into the development of both systems and their linkages.

Results

Vergence and accommodation develop rapidly in the first months of life, with accommodation changing from relatively fixed myopic focus in the neonatal period to adult-like responses by four months of age. Vergence develops gradually and becomes more accurate after four months of age, but has been demonstrated in infants well before the age that binocular disparity detection mechanisms are thought to develop. Hypotheses for this early vergence mechanism are discussed. The relationship between accommodation and vergence shows much more variability in infants than adult literature has found, but this apparent adult /infant difference may be partly attributed to methodological differences rather than maturational change alone.

Conclusions

Variability and flexibility characterise infant responses. This variability may enable the infants to develop a flexible and robust binocular system for later life. Studies of infant visual cue use may give clues to the aetiology of strabismus and refractive error.