Modeling macular pigment optical density effects on photopic and scotopic vision in degraded visual environments

The macular pigment (MP) is an accumulation of the carotenoids lutein, zeaxanthin, and mesozeaxanthin in the central retina. These are derived from dietary sources. MP absorbs light in the 400- to 520-nm range. Consequently, the MP is a spectral filter over the photoreceptors, reducing the effects of internally scattered light and attenuating the short wavelength component of natural sunlight. The average MP optical density (OD) is about 0.2 to 0.6 log units depending on the sample population, whereas the range of MPOD is reportedly 0 to 1.5 log units. Some people can increase their MPOD by increasing their consumption of lutein, zeaxanthin, and mesozeaxanthin, and this may be important for vision in degraded visual environments (DVE). Specifically, nutritional interventions and dietary supplements have produced statistically significant enhancements under laboratory conditions in visual tasks, such as visibility through haze, low contrast target detection, contrast sensitivity, glare resistance and recovery, photostress recovery, dark adaptation, mesopic sensitivity, and enhanced reaction times. The question is whether these enhancements are operationally meaningful or not. The present paper begins to address the question by modeling MPOD effects on the visibility to low contrast photopic and scotopic targets seen under a range of DVE over realistic distances that incorporate atmospheric filtering. Specific model parameters include luminance, target contrast, spectral content, and distance. The model can be extended to estimate the efficacy of MPOD effects on target detection, discrimination, and standoff distances.