Citation

Peckham RH, Hart WM. Highw. Res. Board bull. 1959; 226: 1-6.

Copyright

(Copyright © 1959, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

A new method for estimating retinal sensitivity by determining critical flicker frequency has been completed. A large field of view is kept at a constant and high level of brightness, so that retinal adaptation is consistent throughout measurement of sensitivity. A small area within this field alternates above and below the background brightness for a measured contrast, and at levels such that the 'average' of the extremes equals the background. The contrast is controlled by a unique beam-splitting device with an optical relay, at any chosen contrast from 0 to 50 percent with respect to background. The frequency of alternation of the two beams is accomplished by a synchronous motor operated by an audio-generator and amplifier, from 30 to 70 cycles per second at will. Random order presentation of the stimuli yelds data which can be reduced to psychometric estimates of threshold by probit analysis. Subjects chosen from a large ophthalmic practice, ranging from 8 years up to 80 years of age, have been studied. It has been found that the measure of retinal sensitivity, by means of flicker rate, indicates a superiority in young adults ( 21-31 ) of five or more times above the average of the median adult population (32-50). A comparable depression to one fifth or less in the sensitivity of older adults ( 51-80 ) is also demonstrable. This amounts to a superiority of 25 to 1 or better for young vs. Old adults. Teenagers ( 8-20 ) are comparable to the young adult group, but show greater individual variance, depending in part upon immediately preceding out-of-doors activity before their testing. It is concluded that older drivers ( 50 yrs or more ) should be cautioned, and perhaps examined. Elderly drivers should be persuaded not to drive at night, if at all avoidable. Potential protection of elderly retinas by the use of sunglasses or out-of-doors avoidance is suggested. Support of further research is greatly needed, as this degree of retinal disfunction is a significantly potential cause of accidents due to poor night visibility.