Towards implementation of continuous biologically relevant light measurements at the bedside in the Neonatal Intensive Care Unit.

Preterm infants, when admitted to the Neonatal Intensive Care Unit (NICU), are exposed to an environment that lacks a robust 24-hour light-dark cycle, potentially disrupting the input to their circadian system and developmental outcomes. Accurate quantification of biologically relevant light exposure is critical, yet no standardized frameworks of how to measure and report patient-level light exposure in the NICU are available. We used light loggers to measure continuous melanopic Equivalent Daylight Illuminance (mEDI) in the NICU of the University Medical Center Utrecht. Differences in mEDI values between the logger in the incubator and at the infant's eye-level were quantified across incubator locations and head orientations. Curtain configurations were assessed to visualize the impact of unrecorded environmental changes. Location-specific correction factors, logger adjustments, and head-orientation modifiers were derived to generate corrected infant eye-level mEDI values. This workflow enables feasible and accurate NICU eye-level light quantification, supporting biologically informed circadian care.