Ocular accommodation in human infants.

The present longitudinal investigation evaluated the proficiency of the human ocular accommodation system during the 20-week period after birth. Fourteen human infants were tested at specific intervals during the age of 2 through 20 weeks. At each age the refractive state of the eyes during fixation of a vertical-striped, high-contrast stimulus pattern presented at viewing distances ranging from 10 to 50 cm was measured by dynamic retinoscopy. The accommodative performance of the infants demonstrated the following: (1) the newborn accommodation system executes reasonably appropriate responses to weak dioptric stimuli; (2) accommodative accuracy generally decreases from 2 through 8 weeks of age; and (3) accommodative accuracy increases beyond 8 weeks of age until adult-like levels of proficiency are attained between 16 and 20 weeks. Factors which could affect individual accommodative responses and explanations for the observed developmental pattern of accommodative performance are discussed.