• Based on an illustration by Swaraj Bose, MD.
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    The tangent visual field test at 1 and 2 meters (m). The visual field normally expands on increasing the testing distance from 1 to 2 m. This is due to the increase in the visual angle from X degrees to 2X degrees. In a patient with nonorganic vision loss, the normal expansion of the visual field is absent and remains contracted despite the increase in testing distance.