Abstract
Contrast sensitivity is reduced in older adults and is often measured at an overall perceptual level. Recent human psychophysical studies have provided paradigms to measure contrast sensitivity independently in the magnocellular (MC) and parvocellular (PC) visual pathways and have reported desensitization in the MC pathway after flicker adaptation. The current study investigates the influence of aging on contrast sensitivity and on the desensitization effect in the two visual pathways. The steady- and pulsed-pedestal paradigms were used to measure contrast sensitivity under two adaptation conditions in 45 observers. In the non-flicker adaptation condition, observers adapted to a pedestal array of four 1°×1° squares presented with a steady luminance; in the flicker adaptation condition, observers adapted to a square-wave modulated luminance flicker of 7.5 Hz and 50% contrast. Results showed significant age-related contrast sensitivity reductions in the MC and PC pathways, with a significantly larger decrease of contrast sensitivity for individuals older than 50 years of age in the MC pathway but not in the PC pathway. These results are consistent with the hypothesis that sensitivity reduction observed at the overall perceptual level likely comes from both the MC and PC visual pathways, with a more dramatic reduction resulting from the MC pathway for adults >50 years of age. In addition, a similar desensitization effect from flicker adaptation was observed in the MC pathway for all ages, which suggests that aging may not affect the process of visual adaptation to rapid luminance flicker.
Highlights
Contrast sensitivity is one of the most fundamental functions of the human visual system
Each observer’s MC contrast sensitivity (-Ks), PC contrast sensitivity (-Kp), and PC contrast gain (-log(Csat)) parameters were estimated using Eqs 1 and 2. These estimates were analyzed using the Linear Mixed Model (LMM) to examine the effects of age and flicker adaptation
We aimed to investigate the aging effects specific to the MC and PC visual pathways, as well as the impact of a rapid temporal flicker adaptation on contrast sensitivity in the two pathways at different ages
Summary
Contrast sensitivity is one of the most fundamental functions of the human visual system. It is the ability to detect spatial contrast (e.g., achromatic luminance difference between areas). Many activities of our daily life, such as finding an object, seeing stairs, and noticing a moving object, rely on this ability. Research has shown that evaluation of spatial contrast sensitivity correlates with many higher-order visual functions [1,2,3], provides more information about the visual system, and is a better predictor of daily visual performance than visual acuity [4, 5]. Contrast sensitivity deficits have been observed in many ophthalmic conditions, such as amblyopia [6,7,8,9], glaucoma [10,11,12], diabetic retinopathy [13, 14].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
