Dark Adaptation Threshold (DAT) is a vision test that measures the adjustment of the eye occurring under low levels of illumination. VisiCorp 's VisiOn was a short-lived but influential Graphical user interface -based Operating environment program for IBM PC compatible When light enters the eye, it ultimately reaches the rods and cones, which are two types of cells in the retina. A photoreceptor, or photoreceptor cell, is a specialized type of Neuron (nerve cell found in the Eye 's Retina that is capable of The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Rods handle vision in low light conditions and cones handle color vision and detail. The rods and cones each react differently during the DAT test, and are measured on a graph. The test determines the threshold, or minimum light intensity required to produce a visual sensation in the child's eye. In order to perform this test, the child is asked to sit in the dark for a half hour. This allows the eyes to be most sensitive for the test. Once the eyes have fully adapted, the child stands in front of a black projection screen. Dim spots of light are projected onto the screen, one at a time, on either the right or the left side. The spots get dimmer as the test goes on. The child is asked to point to the spots until he or she can no longer distinguish them. In order to keep the child's attention on the screen, sometimes the doctor will wave a brighter light on the screen to hold the child's interest when the test becomes harder to see. 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. Night vision is the ability to see in a dark environment Whether by biological or technological means night vision is made possible by a combination of two approaches sufficient Once the patient can no longer see the spots, the dark adapted threshold is determined. The DAT test lasts for about 10 to 15 minutes.
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