Effects of nursery illumination on frequency of eyelid opening and state in preterm neonates.

The behaviour of a group of premature neonates was observed under three conditions of ambient illumination defined as either DARK, LIGHT or BRIGHT (mean intensities: 0.9, 109 and 1370 lux). Trends in the data suggested that increasing the level of illumination resulted in a reduction in the proportion of time spent with eyelids open and of the amount of time spent in awake states. However, these effects were small and in most cases failed to attain statistical significance. Sudden offset of light did however produce a transitory increase in eyelid opening for a period of approximately 60 s that appeared to be unaccompanied by any change of state (P less than 0.001). Irrespective of illumination condition, the infants' behaviour was characterized by prolonged periods of eyelid closure which were significantly greater for the lower eye (in mattress contact, mean lid closure = 96.2%) compared to the upper eye (no mattress contact, mean lid closure = 88.25%). The prolonged occurrences of eyelid closure are discussed in relation to visual development and phototoxicity.