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The fixed and dilated pupils of premature neonates
S J Isenberg1, A Molarte, M Vazquez
1Department of Ophthalmology, Jules Stein Eye Institute, Torrance, California.
Insights
Pupil size in preterm infants naturally decreases with age. Light response develops around 30 weeks, so unresponsiveness doesn't indicate blindness until 32 weeks.
Area of Science:
- Neonatal ophthalmology
- Developmental pediatrics
Background:
- Pupil size and light reactivity are crucial indicators of neurological and visual health.
- Understanding normal pupillary development in preterm infants is essential for accurate clinical assessment.
Purpose of the Study:
- To characterize the changes in pupil size and light reflex development in preterm infants.
- To establish age-related norms for pupillary responses in this vulnerable population.
Main Methods:
- Weekly examination of pupil size and light constriction in 30 preterm infants.
- Measurements taken under low (10 ft.-c.) and high (600 ft.-c.) illumination.
- Correlating pupillary measurements with postconceptional age.
Main Results:
- Mean pupil diameter decreased from 4.7 mm at 26 weeks to 3.4 mm at 29 weeks postconceptional age.
- Pupillary light constriction was consistently observed starting at a mean of 30.6 weeks postconceptional age.
- Significant changes in pupil size and light reactivity were noted during early preterm development.
Conclusions:
- Pupil size naturally reduces in preterm infants as they mature.
- A lack of pupillary light response before 32 weeks postconceptional age should not be interpreted as blindness.
- Mydriasis in preterm infants does not necessarily indicate a central nervous system disorder.
Abstract:
We examined on a weekly basis the pupils of 30 preterm infants. In relative darkness (less than 10 foot-candles [ft.-c.] of illumination), the pupils measured a mean of 4.7 mm in the youngest infants (26 weeks' postconceptional age) when the corneal diameter was 7.0 mm. The pupils became progressively smaller, reaching 3.4 mm at 29 weeks' postconceptional age (P less than .001). The pupils did not constrict to the stimulating light (600 ft.-c.) until a mean of 30.6 weeks' (+/- 1 week) postconceptional age. Mydriasis should not be considered indicative of a central nervous system disorder, and a pupil unresponsive to light should not be considered suggestive of blindness until a preterm infant reaches at least 32 weeks' postconceptional age.