Flicker fusion threshold (F.F.T.) means the frequency with which successive flashes of light must occur to just appear to the eye free from flicker. A simple portable machine is described which will deliver flashes of light at any required interval. Patients with hypertension or anemia have a lower than normal F.F.T.; furthermore, administration of nitroglycerin, 0.4 mg. sublingually, or papaverine, intravenously, raises the threshold in patients with hypertension and coronary disease and lowers it in normal individuals. It is suggested that this test may be of use in the diagnosis of equivocal cases and for the evaluation of therapeutic measures.
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