Abstract
Purpose :
Impaired color vision, often a tritan loss, may be an early indicator of visual dysfunction, even when high contrast visual acuity is normal. New technology for clinical color vision testing can separately test contrast detection for red, green, and blue stimuli. Since macular pigment absorbs blue light, blue color contrast sensitivity (BCCS) may be less than expected in those with higher macular pigment optical density (MPOD), which could confound interpretation of BCCS results in the context of suspected disease. We determined the extent to which MPOD can predict the BCCS for targets of different sizes in young, healthy adults without ocular disease.
Methods :
BCCS (ColorDx, Konan Medical) for 4 target sizes, respectively subtending 0.72, 1.43, 2.15 and 7.15 degrees at the viewing distance of 60 cm, was measured in one randomly selected eye of 71 healthy human subjects, aged 22-34 years. Room illumination was low, target duration was up to 5 seconds, and four blocks, separated by 1-5 minutes, were used to present the trials, with stimulus size constant within each block. For each trial subjects identified the gap in an isoluminant Landolt C via a 4-alternative forced choice procedure, and the psi-marginal adaptive method (standard for the clinical instrument) was used to determine threshold. MPOD scores for the same randomly selected eye (heterochromic flicker photometry, QuantifEye, Zeavision) that were obtained 4-12 months earlier for another study by the same author were used for comparison.
Results :
Both MPOD scores and BCCS values were normally distributed. Multiple linear regression, with age, gender, color vision status, number of concussions, and MPOD scores as factors, showed that the linear model including only MPOD significantly predicted BCCS for the smallest (0.72 deg) target (p = 0.002), with the BCCS explaining 11.9 percent of the variability in MPOD scores. For the three larger stimuli, none of the factors evaluated had a significant linear relationship with BCCS.
Conclusions :
BCCS variability for small targets in young, healthy adults can be explained in part by MPOD. We suggest measuring MPOD in subjects with reduced BCCS to small targets before attributing an initially measured tritan loss to central retinal or other pathology of central vision. Further work is needed to establish the relationship between the distribution and density of MPOD and BCCS.
This is a 2020 ARVO Annual Meeting abstract.