Development of accommodation and convergence in infancy.
Paraxial photorefraction was used to assess the development of accommodation and convergence in a large sample of infants under 1 year of age. The infants viewed small dolls placed at various distances (200-25 cm). The majority of infants at all ages demonstrated appropriate convergence for target distance, regardless of manifest refractive error. However, accommodation lagged behind convergence in development. Infants under 2 months tended to demonstrate either flat accommodation responses with a fixed plane of focus at around 30 cm, or accommodated appropriately for near targets, but failed to relax their accommodation sufficiently for the more distant targets. Thus, the focussing error increased with increasing target distance. Since the manifest refractive error was estimated by extrapolating the accommodation function to 0 diopters demand, these infants demonstrated spuriously myopic behavior. After 2 months, the majority of infants showing emmetropic behavior had accommodation responses that changed appropriately with target distance. However, infants with myopic or hyperopic manifest refractive errors displayed a variety of accommodative styles.
Hainline
L
L
Infant Study Center, Brooklyn College, City University of New York 11210.
Riddell
P
P
Grose-Fifer
J
J
Abramov
I
I
D000065:Accommodation, Ocular / Q000502:physiology*; D000375:Aging / Q000502:physiology; D003290:Convergence, Ocular / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D011680:Pupil / Q000502:physiology; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000503:physiopathology