Abstract
Purpose: :
An investigation of the visual changes that occur with age can reveal much about the underlying mechanisms of vision. Rates of decline of different visual functions can be compared to infer whether they are mediated by the same or different underlying optical/neural mechanisms. Furthermore, rates of decline can be compared to changes known to occur within the senescent visual system to elucidate the role of visual system components. In the present study, we investigate the changes that occur with age in four visual functions.
Methods: :
Participants consisted of a sample of young adults (20 to 40y; N=21, age=22.6±4.6y), and a sample of middle-aged and senior adults (50+y; N=16; age=62.3±7.6y). All participants had normal healthy vision and were tested while wearing best correction. Participants were tested using a Computer-Based Instrument (CBI) designed by our laboratory. The CBI, which consists of a laptop computer connected to a calibrated, high-resolution monitor, contains tests of resolution acuity, contrast sensitivity (CS), and vernier acuity that follow nearly identical testing procedures. In addition, all participants completed the ETDRS optotype acuity test. The scores of the two age groups were compared and correlational analyses were conducted to determine whether the visual functions correlated with age.
Results: :
The age groups did not differ on vernier acuity or optotype acuity (both p>0.05). Compared to the 50+ group, the young adults had superior resolution acuity (-0.06 v. -0.23 logMAR, respectively, p=0.001). Although, the groups did not differ on CS at low to mid spatial frequencies (1.5, 3, and 6 cpd, all p>0.05), the young adults had higher CS at high spatial frequencies (12 and 18 cpd) compared to the 50+ group (both p<0.05). Furthermore, of all visual functions, only grating acuity and CS at 3, 12, and 18 cpd were correlated with age (all p<0.05).
Conclusions: :
The results suggest that different visual functions undergo different patterns of age-related changes. Resolution acuity declines with age, whereas vernier acuity and optotype acuity remain relatively stable. CS declines with age, but only at high spatial frequencies. Thus, vernier acuity and optotype acuity appear to be limited by different mechanisms than grating acuity and CS at high spatial frequencies.
Keywords: aging: visual performance • visual acuity • contrast sensitivity