The flicker fusion frequency and its response to nitroglycerin in normal subjects and in patients with cardiovascular disease.

Krasno and Ivy have claimed that the change after sublingual nitroglycerin in the frequency at which a flickering light appears to fuse (f.f.f.) sharply differentiates between cardiovascular normals and patients with coronary and /or hypertensive disease and that this test may be useful in detecting and evaluating such disease. On the basis of a detailed analysis of the original publication and of data on 304 men these claims are denied. Indications for further study of flicker phenomena are discussed and fiducial norms are presented. T HE FUSION frequency (or critical frequency) of flicker is that rate of successive light flashes where the sensation of flicker disappears and becomes the same as that of continuous light. There is reason to believe that the fusion frequency of flicker (f.f.f.) in a subject with normal ocular structures depends on the time parameter of excitability of the visual pathways," 2 primarily of the visual centers.3-' While the literature on the flicker phenomenon goes back over a period of one hundred years, the application to physiologic or clinical stress situations is quite recent. Simonson and co-workers6 found a decrease of the fusion frequency of flicker in fatigue of the central nervous system and in various types of pathology, among others in a group of 21 patients with heart disease.7 This seemed to be in harmony with observations on the fatigability of cardiac Published with the approval of the Chief Medical Director, Veterans Administration Hospital. The statements and conclusions published by the authors are the result of their own study and do not necessarily reflect the opinion or policy of the Veterans Administration. 215 patients in mental as well as in physical work, but no suggestions were made as to the potential value of this method for diagnosis or prognosis of cardiac disease. Recently, Krasno and Ivy' have reported studies on the fusion frequency of flicker before and after the sublingual administration of 0.4 mg. of nitroglycerin and stated, "We believe our results clearly show that the nitro-glycerin-flicker test has revealed the presence of arterial hypertonius or spasm of the retinal arteries in 99 per cent of patients with existing hypertension or coronary arterial disease" (p. 1274). Further, they suggest that "the nitroglycerin-flicker test may prove to be a valuable diagnostic aid (a) for the presence of angina pectoris and coronary occlusion where the evidence is equivocal, (b) for the detection and management of persons who …