Congratulations to Dr. Laor et al. on their study "Sympathetic Pupillary Activity in Infants" (Pediatrics 59:195, February 1977), which concludes that one cause for a relatively miotic pupil in newborns is that "in the first months of life the postganglionic sympathetic nerve releases less norepinephrine ... [which] may be due to a lower number of sympathetic neurons." Pupil size is significantly larger in adulthood than infancy, whether pharmacologically dilated or not. However, neither these authors nor prior workers in this area mention what is probably the single most important reason for this change, the growth of the anterior segment of the eye.