VARIATION OF CRITICAL FLICKER FREQUENCY IN THE NASAL VISUAL FIELD: Relation to Variation in Size of the Entrance Pupil and to Stray Light Within the Eye

THE alternation of a series of spatially superimposed flashes of light which is just seen to flicker is known as the critical flicker frequency. Recently attempts have been made to use this psychophysical measurement in a variety of clinical situations to detect, among other things, early fluctuations in body function, including acid-base changes,¹ cardiovascular changes,² hypoxia,³ intelligence scores,⁴ neurological disorders,⁵ and "fatigue."⁶ Ophthalmologically, there have been attempts to measure the critical flicker frequency in different regions of the visual field in lieu of, or in addition to, the more traditional visual field measurements. Particularly active in such work have been Phillips,⁷ Riddell,⁸ Hylkema,⁹

Weekers and Roussel,¹⁰ and, in this country, Mayer and Sherman¹¹ and Miles.¹² The approach of such investigators has been to set up a series of "norms" depending upon the apparatus and stimulus conditions and to