Abstract
Purpose: A major factor limiting the ability to see in the distance is veiling due to environmental haze. Like skylight, this haze is dominated by short-wave light. Wooten and Hammond (2002) first suggested that yellow filters (in this case, the macular pigments, MP) that absorb this haze could extend visual range. This Visibility hypothesis was tested on subjects with differing MP levels. Methods: 23 healthy subjects (mean = 28.0, s.d. = 8.2) were assessed. Both MPOD and visibility were measured psychophysically and in free view. Visibility was measured (using the methods of limits and constant stimuli) by varying the amount of simulated blue haze (produced with broad-band xenon light and a special interference filter) needed to veil a sine-wave grating (8 cyc/deg). Results: MPOD ranged from 0.11 to 0.85. Visibility thresholds varied by over a factor of 2. MPOD was significantly related to the amount of blue veiling required to lose sight of the grating (r = .62, p < .01). Conclusions: Subjects with higher MP were able to perceive a grating target despite significantly higher levels of haze compared to subjects with lower MP. These empirical data are consistent with the original modeling by Wooten and Hammond.