Abstract
Purpose :
To examine the association between MPOD and rod- and cone-mediated vision in older adults with healthy maculas.
Methods :
Baseline data from the Alabama Study on Early Age-Related Macular Degeneration (ALSTAR) (PMID: 27074381) served as the data source for this cross-sectional analysis. Eyes of participants ≥ 60 years old in normal macular health were included in the analysis. Normal macular health was defined as those eyes at step 1 of the AREDS 9-step classification system based on color fundus photography. MPOD, rod-mediated dark adaptation (RMDA), best-corrected photopic visual acuity, photopic contrast sensitivity, photopic light sensitivity in the macula, mesopic acuity, and low luminance deficit, were assessed. MPOD was estimated at the fovea via heterochromatic flicker photometry. RMDA was estimated using the AdaptDx (PMID: 26522707). Spearman correlation coefficients were used to examine associations between visual function and MPOD. Results were adjusted for age and stratified by gender.
Results :
A total of 731 eyes were analyzed. In the overall cohort, MPOD was unrelated to RMDA, photopic acuity and contrast sensitivity, mesopic acuity, and low luminance deficit. Greater MPOD was associated with better macular light sensitivity (average of 16 points in central 9° of macula), rho = 0.100, age-adjusted, p = 0.007. When stratified by gender, this correlation was 0.131 among females (n = 495; age-adjusted, p = 0.0035) and 0.033 among males (n = 234; age-adjusted, p = 0.618).
Conclusions :
In a large sample of older adults in normal macular health, MPOD is unrelated to RMDA, contrary to an earlier report on a small sample (PMID: 24413682). However, better cone-mediated light sensitivity in the macula was associated with eyes with greater MPOD, a finding that was limited to females. Other measures of cone-mediated function in the fovea were unrelated to MPOD. The positive relationship of MPOD with cone vision and not rod vision resonates with recent evidence that Müller cells are the major xanthophyll reservoir in human macula, while also providing services like retinoid processing and synaptic insulation to cones exclusively. The gender difference is consistent with evidence for a broader MPOD distribution in women than in men that could affect sensitivity outside the fovea.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.