THE FUSION frequency of flicker is that state of successive light stimuli which appear to the eye to be a continuous light and free from any flickering sensation. It depends upon chronaxie, latent period, refractory period of the retina, visual pathways, and visual centers and as a result may indicate the excitability or depression of the visual system, and perhaps of the entire central nervous system. Flicker frequency fusion has no correlation with the visual acuity and depends probably on a visual sensation not at all related to the acuity of vision. A Maddox rod of clear color and large diameter placed before the eye reduced the visual acuity to a minimum; yet the flicker fusion frequency was not affected.
While visual acuity depends upon the ability of the eye to resolve two separate stimuli separated in space, flicker perception depends upon the ability of the eye to resolve two
GARNER LL, CARL EF, GROSSMAN EE. EFFECT OF CIGARETTE SMOKING ON FLICKER FUSION THRESHOLDClinical Observations on Normal Smokers and Nonsmokers. AMA Arch Ophthalmol. 1954;51(5):642-655. doi:10.1001/archopht.1954.00920040652008