Dark Adaptation Threshold (DAT) is a vision test that measures the adjustment of the eye occurring under low levels of illumination.
When light enters the eye, it ultimately reaches the rods and cones, which are two types of cells in the retina.
The test determines the threshold, or minimum light intensity required to produce a visual sensation in the child's eye.
Once the eyes have fully adapted, the child stands in front of a black projection screen.
When an infant is being tested, an observer with a night vision camera records the head and eye movements of the child as they look at the spots.