The present method describes a new method for the measurement of dark adaptation. The dark adaptation status of subjects may ten be used to identify those subjects who are at risk of developing and/or who are currently suffering from a variety of disease states having their clinical manifestations in impaired dark adaptation. The disease states include, but are not limited to, age related macular degeneration, vitamin A deficiency, Sorsby's Fundus Dystrophy, late autosomal dominant retinal degeneration, retinal impairment related to diabetes and diabetic retinopathy. An apparatus for administering the test method described is also provided.