THE EFFECT OF FIELD-OF-VIEW SIZE ON STEADY-STATE PUPIL DIAMETER

Studies of the relationship between luminance and pupil diameter have produced widely differing results. This research note explores the pos sibility that this is due, in part, to differences in the size of the adapting fields used by various workers. We present measurements of pu pil diameter as a function of luminance for a variety of field subtens es. The results indicate a consistent trend for smaller subtenses to p roduce less pupil constriction. For field diameters of up to 25 degree s, replotting the data in terms of corneal flux density (i.e. the prod uct of luminance and subtended area) causes an approximate convergence onto a single function described by D = 7.75-5.75 [(F/846)(0.41)/((F/ 846)(0.41) + 2)] where D is the pupil diameter (mm) and F is the corne al flux density (cdm(-2)deg(2)). This equation should be of some pract ical use in estimation of natural pupil diameter.