Cameron Wysocky¹, Jacob Harth¹, Lisa Renzi-Hammond¹, Billy Hammond¹; ¹University of Georgia

Introduction: A long-standing question in Vision Science is why, under certain conditions, and all things equal (e.g., acuity), some individuals can see farther than others. A common explanation is the limiting effects of short-wave dominated light scatter on objects near the horizon (so-called blue haze). It has been argued for nearly a century that this may be partly why so many animals evolved intraocular blue-absorbing filters (i.e., to cut through this haze and enhance the contrast of distant targets). Humans also possess yellow foveal macular pigments (MP), and past data suggest that these pigments also serve this purpose. In this study, we provide additional data on the effect of MP and blue haze, on contrast sensitivity at multiple spatial frequencies. Methods: Fifty-eight healthy participants (N = 58; 18-28 years; M = 20.45 ± 2.90, 73% female, 33% non-White) with 20:40 uncorrected visual acuity or better, were assessed. MP optical density (MPOD) was measured using heterochromatic flicker photometry. Visual range (i.e., how far an individual can see in the distance) was measured by quantifying the amount of simulated blue haze (broadband xenon light paired with a blue-sky interference filter) necessary to completely obscure sinusoidal target gratings (3.2, 8, and 16-cpd). Results: MPOD was significantly related to the amount of blue haze required for participants to lose sight of the 3.2 (r(56) = .54, p < .001) and 8-cpd (r(56) = .36, p < .01) gratings. The relationship between MPOD and the 16-cpd grating was not significant (r(47) = -0.03, p = .86). Conclusions: MPOD is associated with increases in the visibility of low and medium spatial frequency targets when measured through simulated blue haze. This relationship does not extend to high spatial frequencies, indicating that individual differences in resolution acuity and target size may influence MP’s effect on visual range.