FOVEAL FLICKER SENSITIVITY IN HEALTHY AGING EYES .2. CROSS-SECTIONAL AGING TRENDS FROM 18 THROUGH 77 YEARS OF AGE

Foveal flicker contrast sensitivity was measured for healthy adults at temporal frequencies from 2.5 to 50 Hz. The first experiment compared two-interval forced-choice (2IFC) and yes-no detection (Y-N) testing procedures for younger (19-33-year-old) and older (67-73-year-old) obs ervers. The 2IFC technique resulted in higher absolute estimates of se nsitivity. However, within a method, relative differences were similar . Therefore the two methods gave similar estimates of temporal contras t-sensitivity change with age. Experiment 2 compared 89 observers from 18 through 77 years of age to explore the effect of the time course o f aging on flicker sensitivity. The 2IFC procedure was used, and retin al illuminance changes with age were controlled. Significant overall l osses in contrast sensitivity were found for the 45-54, 55-64, and 65- 77-year-old age groups. Overall sensitivities for the 35-44-year-old g roup were comparable with or (not significantly) higher than those for the 18-24- and 25-34-year-old groups. The results suggested that (1) foveal temporal contrast sensitivity does not decline until after 44 y ears, (2) losses after 44 years are in amplitude but not in temporal r esolution of the visual response, and (3) the mean rate of loss is app roximately 0.78 decilog per decade after 44 years. These results are c onsistent with the existence of three phases of development of tempora l contrast sensitivity over the life span. The results also emphasize the importance of including healthy-eyed age-matched controls in studi es of flicker sensitivity in visual dysfunctions that affect mainly ol der adults.