Abstract
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.
Highlights
Research and development of countermeasures for degraded visual environments (DVEs) commonly focuses on technologic solutions to transient ambient conditions
The model results suggest that the impact of macular pigment (MP) on luminance Weber contrast (WC) differs between photopic and scotopic vision
Any contrast enhancement or reduction due to MPOD was of greater magnitude under scotopic conditions than photopic conditions
Summary
Research and development of countermeasures for degraded visual environments (DVEs) commonly focuses on technologic solutions to transient ambient conditions. This approach typically views “degraded visuals” as an intrinsic characteristic of the environment, separated from the human operator. Everything which occurs prior to transduction of photons into neural signals by the photoreceptors contributes to an operator’s “visual environment,” but much of this is not captured in the technologycentric DVE mitigation framework. The “E” portion of DVE is typically everything outside of the cockpit, including changes in lighting, fog, sand, smoke, and dust, which contribute to the “DV” portion. The pilot’s visual environment includes the outside world, but the windshield, any obstructions to the windshield, the interior of the cockpit, any worn filters (such as sunglasses), the pilot’s refractive elements (i.e., corrective eyewear, the cornea, and the crystalline lens), the aqueous and vitreous humors (including any debris present), and the macular pigment (MP)
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