A: Your AMD questions answered:
OCULAR NUTRITIONAL SUPPLEMENT RESEARCH
Nutrition is a key modifiable factor in preventing and slowing the progression of AMD — no other preventative treatments are currently available.
While research in this area is constantly evolving, and it is up to the clinician to stay abreast of new findings, the evidence for supplements in reducing the progression of AMD is extensive. The AREDS study shows that a combination of high-dose antioxidants and high-dose zinc, reduces the five-year risk of progression from intermediate to advanced AMD by 25%. This formulation was modified in AREDS 2 to 10 mg lutein and 2 mg of zeaxanthin, along with the elimination of beta-carotene, due to the associated risk of lung cancer.
Beyond the AREDS formulation, supplementation is available with the three macular carotenoids — lutein, zeaxanthin, and meso-zeaxanthin. In combination with coantioxidants, the three carotenoids “can have a meaningful effect on visual function,” according to the Central Retinal Enrichment Supplementation Trials (CREST). CREST 2 evaluated two formulations on patients who have nonadvanced AMD: one with coantioxidants and the three carotenoids, and a second with coantioxidants and lutein and zeaxanthin. Both groups showed significant increases in macular pigment, improvements in contrast sensitivity and other visual function measurements.
The AREDS study recommends supplementation for AMD patients who have early and intermediate disease. (Early AMD is defined by the size of drusen, which is medium. Intermediate AMD involves either large drusen or medium drusen, plus pigment.) AREDS did not address preventing AMD in healthy patients. Other studies of healthy patients have shown improvements in macular pigment optical density and visual function with supplementation of the macular carotenoids. For those patients who have no evidence of the disease nor a family history, I recommend these patients use multivitamins. I also recommend better nutrition and lifestyle modification, such as the increased consumption of foods rich in carotenoids (kale, spinach, sweet potatoes, etc.), consistent exercise and discontinued smoking.
There is a lack of consensus regarding the effect of high-dose antioxidants and zinc on AMD, particularly in a certain genotype, namely the complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) gene. A recent study, published in Ophthalmology 2018, shows that CFH and ARMS2 do not predict a response to antioxidants and zinc in AMD patients. While yet another recent study, published in the Proceeding of the National Academy of Science 2018, reveals that CFH and ARMS2 genes do influence the likelihood of progressing to advanced AMD.
The American Academy of Ophthalmology (AAO) does not recommend routine genetic testing at this time. Researchers continue to investigate a relationship between AMD and genetics. Optometrists should stay abreast of such science. For eye care practitioners who are concerned, zinc-free formulations are available.
For a list of AMD supplement manufacturers, consult bit.ly/PMOAMDTx .
In addition to prescribing an ocular nutritional supplement, optometrists can prescribe action steps related to modifiable risk factors for AMD. By far the most important modifiable risk factor for AMD is smoking tobacco products, and it remains the only established causative factor for AMD. Compared with someone who has never smoked, current smokers have two to three times greater risk of developing the disease. In addition, smokers develop AMD at a younger age than nonsmokers, and they have a higher risk of disease progression.
Smoking cessation results in a risk reduction that increases with duration of abstinence from tobacco. Several long-term, population-based studies show that former smokers are at only a slightly higher risk than individuals who have never smoked.
Light-induced (sunlight and blue light) oxidative damage is another modifiable risk factor that should be addressed in AMD patients. Newer spectacle lenses are designed to selectively filter or block UV or blue-violet light.
Low macular pigment is another significant AMD modifiable risk factor. Macular pigment is comprised of the carotenoids lutein, zeaxanthin and meso-zeaxanthin, which have both blue light-filtering and antioxidant properties. Low macular pigment is associated with low dietary intake of foods, such as spinach, kale and eggs, rich in these compounds. Other factors contributing to low macular pigment include genetics, obesity and, again smoking. Macular pigment can be clinically tested using heterochromatic flicker photometry, known as MPOD.
Another way to become proactive in treatment is to utilize advances in technology, which aid in our ability to detect and manage AMD early. Fundus photography is useful for classifying the stage of AMD, documenting pathology changes over time and educating patients about their disease.
Spectral-domain optical coherence tomography (SD-OCT) can aid us in detecting signs of choroidal neovascularization (CNV) and geographic atrophy (GA), the latter of which typically shows enhancement of the underlying choroid and loss of the retinal pigment epithelium (RPE) hyperreflectivity with variable involvement of the overlying neurosensory retina.
OCT angiography allows for visualization of the CNV vascular network. In addition, enhanced-depth imaging provides improved visualization of the choroid, which allows for the assessment of choroidal changes in AMD. Fundus autofluorescence demonstrates a reduction in the autofluorescence signal that originates largely from RPE and is absent in the region of the GA.
Additionally, dark adaptation testing can aid in the identification of early functional loss in AMD patients, as well as those at risk for AMD, yet who have no clinical signs. (For a list of diagnostic devices, consult OM’s Practicing Medical Optometry’s “Diagnostic Devices” found at bit.ly/PMOAMDDx .)
AMD remains a formidable challenge, resulting in millions of Americans losing their sight. Therefore, continued patient education and the importance of yearly comprehensive eye exams, as well as research and delivery of state-of the art care, are necessary. OM