The effects of age on spatial frequency perception in human subjects

Visual performance was measured in sixty-six subjects aged from 5 to 94 years. The curve of contrast sensitivity against spatial frequency was obtained for each subject. This curve had a peak contrast sensitivity in the 2-6 c/deg (cycles/degree) range with the fall-offs to either side of the peak described, on a double logarithmic plot, by straight lines. With advancing age, the position of the peak sensitivity remained unchanged but there was an overall decrease in contrast sensitivity. The highest spatial frequency which could be perceived remained constant up to 50 years, thereafter it fell with increasing age. The slope of the low frequency straight line remained unchanged while that of the high frequency straight line fell with increasing age, i.e. the loss of contrast sensitivity was greater for middle range spatial frequencies than for higher spatial frequencies. The possible site of these changes, i.e. the optics of the eye, the retina/brain or higher decision making centres, is discussed.