Early visual development: implications for the neonatal intensive care unit and care.

Much of the early development of the human visual system occurs while the preterm infant is in the neonatal intensive care unit (NICU). Critical events and processes happen between 20 and 40 weeks' gestational age, before the onset of vision at term birth. Knowledge of the development of the visual system and the timing of the processes involved is essential to adapting NICU care to support all neurosensory development including visual development.