Found a nice article on the different xanthophylls and the eye:
Lutein, Zeaxanthin, and meso-Zeaxanthin: The Basic and Clinical Science Underlying Carotenoid-based Nutritional Interventions against Ocular Disease
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4698241/
I'll post some choice quotes and pictures with some commentary:
meso-zeaxanthin is found in the eye
believed to be formed at the macula by metabolic transformations of ingested carotenoids
Just in case you were wondering
monkey eyes are relatively easier to obtain soon after death compared to human eyes
The 3 xanthophylls discussed have varying distribution throughout the eye
Near the fovea there is twice as much zeaxanthin and meso-zeaxanthin as lutein; but, in the peripheral retina, this relationship is reversed, and zeaxanthin and meso-zeaxanthin levels are half as much as those of lutein... In the central retina, equal concentrations of lutein, zeaxanthin and meso-zeaxanthin are present; however, the ratio of meso-zeaxanthin to zeaxanthin decreases with the increased eccentricity to the fovea
A nice picture of that
Getting zeaxanthin and not meso-zeaxanthin in your supplement looks even more important, since meso-zeaxanthin probably naturally occurs in the eye after transformation from lutein
This conformational similarity of meso-zeaxanthin to lutein makes it more likely that lutein rather than zeaxanthin is the immediate precursor to meso-zeaxanthin... conversion of lutein to meso-zeaxanthin most likely takes place in the eye
This figure shows how xanthophylls neutralize ROS from blue light
There is something to be said about reducing unstable omega-6 polyunsaturated fats from your diet and replacing them with omega-3 and monounsaturated fats, which provide stability to cell membranes and with less potential for ROS generation
The potential for generation of ROS in the retina is high. The outer retina, especially membranes of the outer segments of the photoreceptors, has high concentrations of polyunsaturated fatty acids that are susceptible to photo-oxidation
Cool
With aging, the RPE gradually accumulates lipofuscin... There is solid experimental evidence that... a component of lipofuscin, can damage the RPE, is toxic to mitochondria, and induces apoptosis of cultured RPE cells when exposed to blue light... When RPE cells are treated with lutein, this phototoxic effect is reduced greatly... The presence of lutein and zeaxanthin has further been shown to reduce the amount of lipofuscin formed in cultured RPE cells and in vivo
Take it with a fatty meal
Given their hydrophobic nature, there is evidence that consuming carotenoid-rich foods in the presence of oils or cholesterol may increase their uptake
Some answers on the safety of a high lutein dose. 1 mg / kg of bodyweight
the European Food Safety Authority (EFSA) Panel on Food Additives and Nutrient Sources added to Food established an acceptable daily intake of 1 mg / kg bodyweight / day for lutein preparations derived from marigold
Although you could probably take much more if you wanted
The no observed-adverse-effect-level (NOAEL) for lutein/zeaxanthin concentrate was determined to be 400 mg/kg bodyweight/day
Absorption spectrum (MP is macular pigment)
The absorption maximum of lutein is 445 nm, while the maxima of zeaxanthin and meso-zeaxanthin are 450 nm... MP absorbed light between the wavelengths 430 nm and 490 nm, with maximum absorption taking place at ∼460 nm
HDL cholesterol transports xanthophylls to the eye. We love our HDL, folks.
The Wisconsin hypoalpha mutant (WHAM) chicken, a natural animal model of HDL deficiency, has a >90% reduction in plasma HDL.... When these chickens are fed a high-lutein diet, lutein levels increase in plasma, heart, and liver, but not in retina, suggesting that HDL is critical for delivery of carotenoids to retinal tissue
Article then goes on to identify some gene polymorphisms that could impair lutein and zeaxanthin binding in the eye and lead to problems.
Primates have very similar eyes to humans
RPE are retinal pigment cells, and light must pass through them to reach your photoreceptors.
Some more support for omega-3s (n-3 fatty acids)
In xanthophyll-free monkeys, they observed a dip in the RPE cell density profile at the foveal center. They also observed a difference in the RPE profile depending upon the level of n-3 fatty acids. Thus, they concluded xanthophylls and n-3 fatty acids are essential for the development and maintenance of RPE cells
Article then talks about rodent and avian models, but their eyes aren't similar enough.
Very nice
There is a growing and evidence-based consensus that MP is important for optimal visual performance because of its blue light-filtering properties and consequential attenuation of chromatic aberration, veiling luminance, and blue haze
A picture on the absorption spectrum of macular pigment (which is made up of lutein and zeaxanthin)