The accommodative pupil responses of children and young adults at low and intermediate levels of ambient illumination.

Accommodative pupil constrictions were compared between 27 children (9-10 years) and 13 young adults (22-26 years) in order to clarify the issue whether or not children have such a response. Accommodative stimuli of 4 and 7 diopters were used to elicit the response and experiments were performed at 5 and 100 lux in order to investigate whether the level of ambient light has different effects on developing and mature visual systems. The accommodative pupil response is present in children, but weaker than in adults. Different levels of ambient light lead to only minor additional differences between children and adults. The weaker accommodative pupil response of children may be a consequence of their superior accommodative ranges, which make it unnecessary to close the pupil to increase depth of field. Adults, in contrast, may do better with smaller pupils that reduce accommodative demand because of increased depth of field. A mature human visual system may furthermore be better tuned to handle dimmer and thus noisier images in the photopic range than the developing visual system of a child.