Convergence and Accommodation Development Is Preprogrammed in Premature Infants

Horwood, A. M.,Toor, S. S.,, Riddell, P. M. Invest Ophthalmol Vis Sci 2015. : 56 (9) 5370-80 10.1167/iovs.14- 15358

Premature babies are at higher risk of squinting and needing glasses.
Some of this may be because a mis-match of developing systems means that their early binocular vision could be damaged by poor eye focus control.

Purpose

This study investigated whether vergence and accommodation development in preterm infants is preprogrammed or is driven by experience. METHODS: Thirty-two healthy infants, born at mean 34 weeks gestation (range, 31.2-36 weeks), were compared with 45 healthy full-term infants (mean 40.0 weeks) over a 6-month period, starting at 4 to 6 weeks postnatally. Simultaneous accommodation and convergence to a detailed target were measured using a Plusoptix PowerRefII infrared photorefractor as a target moved between 0.33 and 2 m. Stimulus/response gains and responses at 0.33 and 2 m were compared by both corrected (gestational) age and chronological (postnatal) age.

Results

When compared by their corrected age, preterm and full-term infants showed few significant differences in vergence and accommodation responses after 6 to 7 weeks of age. However, when compared by chronological age, preterm infants’ responses were more variable, with significantly reduced vergence gains, reduced vergence response at 0.33 m, reduced accommodation gain, and increased accommodation at 2 m compared to full-term infants between 8 and 13 weeks after birth.

Conclusions

When matched by corrected age, vergence and accommodation in preterm infants show few differences from full-term infants’ responses. Maturation appears preprogrammed and is not advanced by visual experience. Longer periods of immature visual responses might leave preterm infants more at risk of development of oculomotor deficits such as strabismus.