AMD Prevention Measures: Do They Have Merit?
COORDINATED BY ABDHISH R. BHAVSAR, MD
Welcome to Face Off, a column that explores controversial topics in the diagnosis and management of retinal diseases. In this issue, we will explore AMD prevention measures and if they have merit.
Although a well-designed, large, multicenter, randomized clinical trial has been conducted to evaluate the issue of antioxidant vitamins and minerals for risk reduction in AMD patients, the supplements studied included only some of the supplements that could potentially be beneficial to the retina or for AMD patients. This leads to the question:What do you consider when prescribing vitamins to your patients with AMD or at risk for AMD? This month, Face Off offers some answers.
Another area of controversy addressed in this column is blue-light filtering technology and what the potential impact is on the eye and on AMD.
VITAMIN THERAPY: AREDS SUPPLEMENTS
SUSAN BRESSLER, MD
When AREDS was designed and initiated, other carotenoids that are naturally found in the macula in high concentrations, such as lutein and zeathanthine, were not commercially available as oral supplements, and were not included in the investigation.
Fortunately, the AREDS clinical trial identified that individuals at risk for progression to advanced AMD had reduced rates of progression when assigned to the combination supplements, as compared to placebo. Overall, use of the AREDS combination supplement decreases the risk of progression by 25% over 5 years and 27% over 10 years.
Additional data from epidemiologic studies has suggested that lutein/zeathanthine and fish oil, may also play a protective role in reducing rates of advanced AMD. These observations have led to the conduct of AREDS2.We do not anticipate results from this clinical trial for at least 5 to 7 years.
Until AREDS2 identifies a safe and efficacious role for lutein/zeathanthine or fish oil and provides data showing the interaction of these agents with the original AREDS formulation or the AREDS formulation without betacarotene, I will continue to recommend the original AREDS formulation for my AMD patients at risk of progression.
VITAMIN THERAPY: AREDS PLUS ANTIOXIDANTS
JOHANNA SEDDON, MD
Many observational studies designed specifically to evaluate diet and AMD have been published, starting in 1994, showing that diets rich in antioxidants are protective, especially for exudative AMD. The carotenoids, lutein and zeaxanthin, lead that list of potentially helpful antioxidants in foods such as spinach, as well as fish and other omega-3 fatty-acid rich foods. A large multicenter randomized trial also showed in 2001 that antioxidants in supplement form are protective and reduced rates of progression of AMD. Therefore, I recommend that my AMD patients eat foods with lutein and omega-3s in addition to the AREDS formulation.
BLUE-LIGHT FILTERING TECHNOLOGY
KOUROUS REZAEI, MD
Exposure to blue light results in the production of reactive-oxygen species, which subsequently lead to cellular apoptosis. In aged retinal pigment epithelium (RPE) cells (patients with AMD), the presence of lipofuscin and its fluorophores, including A2E, further increases the toxicity of blue light. The yellow discoloration of the natural lens with age may be a naturally appearing mechanism to protect the RPE cells from the high-energy blue light.
Removal of the cataract in patients with AMD and implantation of a colorless lens (blocking only UV light) would increase the exposure of already degenerating RPE cells to blue light and may boost their deterioration and their loss of functional viability. One may hypothesize that the implantation of a yellow-tinted lens, which mimics the color of the natural lens, would reduce the risk of blue light exposure.
Confirming previous data, our recent publication shows that the AcrySof Natural (Alcon, Fort Worth, Texas) filter significantly reduces the blue-light-induced apoptosis in RPE cells when compared to AcrySof filter.1 This is due to the blocking effect of the filter on the blue wavelength, reducing the energy reaching the cells. RPE cells in our experiments did not contain lipofuscin fluorophore A2E, indicating that even in the absence of lipofuscin the blue light may be toxic. Our results indicate that blue-filtering lens protects RPE cells from blue-light-induced apoptosis.
BLUE-LIGHT FILTERING TECHNOLOGY
MARTIN MAINSTER, MD
Blue-blocking (filtering) IOLs reduce scotopic vision, which decreases with aging due to rod photoreceptor loss and pupillary miosis. Reduced dark adaptation increases the risk of falling and night-driving difficulties. Blue-blocking IOLs also reduce circadian photoreception, which is vital for good physical and mental health and decreases due to age-related miosis and crystalline lens yellowing. Blue-blocking IOLs provide 20% less protection than 53-year-old crystalline lenses. Most AMD occurs in phakic adults over 60, so 53-year-old lenses do not prevent it. Thus, blue blockers offer 20% less protection than something that doesn’t work. Acute phototoxicity can injure the retina but not simulate AMD, just as scalding water can scar skin but not simulate a lifetime of normal bathing. Nine of the 11 major epidemiological studies found no correlation between AMD and lifetime light exposure. CMS concluded in 2005 that “the relationship between blue light and AMD is speculative and not proven by available evidence.” You need light to see. Blue-blocking is not evidence-based medicine and decreasing blue light photoreception is not justified by the scientific facts.2
1. Sparrow JR, Miller AS, Zhou J. Blue light-absorbing intraocular lens and retinal
pigment epithelium protection in vitro. J Cataract Refract Surg. 2004;30:873-878.
2. Mainster MA. Violet and blue light blocking IOLs. Br J Ophthalmol. 2006;90:784-792.
Abdhish R. Bhavsar, MD, is an attending retina surgeon at the Phillips Eye Institute, director of clinical research at the Retina Center, PA, in Minneapolis, and adjunct assistant professor at the University of Minnesota. Email him about Face Off at email@example.com.
Retinal Physician, Issue: March 2007