An Eye On Health

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VISION is critical in our daily lives and maintaining good vision is key to maintaining a good quality of life.  Of the more than 600 plant pigments called carotenoids found in nature, only two carotenoids, zeaxanthin and lutein, selectively accumulate in the retina, macular and lens.  

Zeaxanthin is the dominant component in the centre of the macula, while lutein dominates at the outer edges. The eye is selective and preferentially places dietary zeaxanthin in the very centre of the macula, the most critical area for central vision with the greatest need for protection.  

Observational studies have noted that higher dietary intakes of zeaxanthin and lutein is related to reduced risk of cataracts and age-related macular degeneration, two eye conditions for which there is minimal options when it comes to effective prevention.  

Researchers speculate that these carotenoids may promote eye health through their ability to protect the eyes from light-induced oxidative damage and ageing through both their antioxidant actions as well as their ability to filter out UV light.  

The eye’s natural sunglasses 

Plants synthesise zeaxanthin and lutein to harvest light energy and protect against excessive light. It now appears that humans also utilise these pigments to protect the eyes from excessive interaction with the damaging effects of light.  

This function of zeaxanthin and lutein is similar to a set of “natural sunglasses” for the tissues of the eye.  Both zeaxanthin and lutein absorb the very high-energy and most damaging portions of the light spectrum (ultraviolet blue). The absorption of the high-energy light spectrum is critical for the protection of the lens, retina and macular portions of the eye. High-energy blue light also generates “free radicals” that cause damage to the tissues of the eye. Zeaxanthin and lutein are also antioxidants that stop free radicals. 

Acting as a filter to shield against harmful blue light and as antioxidants, both zeaxanthin and lutein help to reduce the risk of age-related macular degeneration (AMD) and cataract, the leading causes of blindness in the world. 

Zeaxanthin and macular degeneration 

To understand how zeaxanthin helps to delay the onset of macular degeneration or slows its progression, one needs to know the different ways the retina and macular process light.  

When light hits the retina, it passes directly to the photoreceptor cells where it is processed. In the macular, the light has to first pass through zeaxanthin and lutein on its way to the photoreceptor cells. Although zeaxanthin and lutein belong to the same carotenoid family, they are slightly different in their chemical structure, which makes zeaxanthin able to function more effectively than lutein in the macular. This may account for the macular’s preference for zeaxanthin over lutein. 

In the retina, the concentration of lutein is twice that of zeaxanthin. In the macular, the concentration of zeaxanthin is twice that of lutein.  

Many scientists now believe that the reason why zeaxanthin is highly concentrated in the macular is because of its antioxidant properties and also because it is a more efficient “filter” of light. 

Since the body cannot synthesise lutein and zeaxanthin, we need to obtain it from our food. As we grow older, the concentration of lutein and zeaxanthin decline, leaving the eyes susceptible to age-related disorders – cataracts and AMD (age-related macular degeneration).  

Taking at least 6mg to 10mg of lutein and 5mg of zeaxanthin daily help to increase the concentration of lutein and zeaxanthin in the lens, retina and macular. Most eye supplements in the market contain lutein together with tiny amounts of zeaxanthin – in the range of micrograms. These concentrations are too little to be of benefit to eye health. You may have to purchase both lutein and zeaxanthin separately to obtain the maximum benefits of both in terms of potency. 

One can choose to take either lutein or zeaxanthin alone for the prevention of age-related eye disorders. However, if one already has some form of age-related eye disorder (cataract, AMD, retinopathy), it is advisable to take both lutein and zeaxanthin.