Measurements of Pupillary Responses to Light in Term and Preterm Infants

Abstract

Dynamic pupillometry of very young subjects presents a significant practical and technological challenge. In consequence, there have been limited reports on the dynamics of the pupil light reflex (PLR) in infants and none on those born prematurely. The purpose of this study was to develop an infrared (IR) pupillometer specifically for use in situ (i.e., within cot or isolette) and to quantify the latency and amplitude of infants' pupillary responses to light as a function of postmenstrual age. Recordings of 2.5-s duration began 500 ms before the presentation of a 500-ms step luminance change (18–39 cd · m^{− 2}) of an LCD display positioned 30 cm in front of a supine infant. Pupillary responses were obtained from 10 infants: five were born within 20 days of their expected due date and recordings were undertaken within three days of birth. The remaining five infants had been born preterm and their postmenstrual age (PMA) was still less than 280 days (full term) at the time of the recording. Pre-response pupil diameter increased monotonically with infant PMA. PLR amplitude and latency decreased with increasing PMA. Conventional dynamic IR video-pupillometry, albeit with a number of situation-specific adaptations, permits the measurement of pupillary responses to light in newborn term and preterm infants within a clinical setting. The characteristics of the early maturation of the pupillometer system can be quantified in this manner.

KEYWORDS:

• Infant
• pupil light reflex
• pupillometry

Notes

*Calculated post hoc, the power for a test of association between the measured pupil variables and PMA ranged from 0.33 to 0.65 (alpha = 0.05).