Macular Pigment and Diabetes
Learn why maintaining a healthy macular is so important.
By A.Paul Chous, MA, OD, FAAO
The macula is the central part of the eye's retina, the light-sensitive membrane lining the back wall of the eye that transmits electrical impulses to the optic nerve and brain. The macula is responsible for detailed and color vision (for example, the ability to read and recognize faces or to correctly match clothing of similar colors). A number of diseases affect the macula, including macular degeneration and diabetes, and may profoundly affect people's ability to perform daily functions — so maintaining a healthy macula is of utmost importance.
The macula contains three carotenoid (yellowish, organic) pigments — lutein, zeaxanthin and meso-zaexanthin — that serve a variety of functions, including absorption of high-energy ultraviolet and blue light (they act as a kind of internal sunglass) and scavenging (neutralizing) injurious free radicals that damage retinal cells. Collectively, these three substances are known as "macular pigment" and the amount of these found within a person's retina is referred to as "macular pigment optical density" or MPOD. People with higher MPOD have been shown to have less photophobia (light sensitivity), better contrast sensitivity (the ability to distinguish an object from other objects or background with similar lighting – like a grey car on grey street on a cloudy day), better ability to tolerate glare from oncoming lights, and reduced risk of developing age-related macular degeneration.
Recently, research has shown that people with diabetes have lower MPOD levels than their age-matched peers, and that diabetic retinopathy and its progression also are both associated with lower MPOD levels. Moreover, increasing MPOD with supplemental lutein and zeaxanthin has been shown to improve visual acuity, contrast sensitivity and swelling of the macula in patients with non-proliferative diabetic retinopathy (Application of Lutein and Zeaxanthin in nonproliferative diabetic retinopathy, Int J Ophthalmol. 2011; 4(3): 303–306.)
Lutein and zeaxanthin cannot be made by the body and must come from dietary sources (excellent sources include kale, collard greens, and orange peppers), whereas meso-zeaxanthin is converted from lutein within the macula itself. Dietary deficiencies of lutein and especially zeaxanthin are prevalent in the US population. It is notable that the center of the macula has a 2:1 ratio of zeaxanthin to lutein (see figure below)
There is growing evidence that increasing macular pigment through diet and/or supplementation may lessen the chances of developing diabetic retinopathy and may improve vision function in patients with both diabetes and diabetic retinopathy. It is also worth noting that higher blood levels of lutein and zeaxanthin are associated with a lower risk of developing type 2 diabetes in the first place.
MPOD can be measured quite easily with a special test that takes only a few minutes at your eye doctor's office. I now measure MPOD in all of my patients with diabetes and prediabetes, have found that supplemental lutein and zeaxanthin improves vision in the majority of patients with low MPOD scores, and would encourage any patient with diabetes to ask your eye doctor about your macular pigment levels.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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