Contemporary AMD Management Strategies, Part 1
BY LEO SEMES, OD, FAAO
Age-related macular degeneration (AMD) may become the most significant cause of reduced vision in patients over age 50 by the end of this decade. We know there are a number of identified and proposed risk factors (See Table 1) and that there is a limited array of treatments. Clinically, AMD is neovascular or non-neovascular. Other designations include early and late. Most cases are non-neovascular, but the majority of significant vision loss is among the neovascular group. This month I will focus on non-neovascular AMD.
Results from the recently released Age-related Eye Disease Study (AREDS) suggest that antioxidant vitamins plus zinc provide a treatment benefit among patients with moderately advanced non-neovascular AMD. This seven-year prospective placebo-controlled trial had well-defined entry criteria and endpoints. It followed over 3,600 patients. Subjects were assigned to antioxidant, zinc, antioxidant plus zinc or placebo arms. Follow-up averaged six years. The study formulation's dose of zinc is high compared to minimum daily requirements.
TABLE 1: AMD-associated Risk Factors
While the benefit may be considered small (mean risk reduction was about 25 percent), maintenance of visual acuity in an elderly population may translate into improved quality of life or continued independence.
Another important outcome from AREDS was staging of non-neovascular AMD. The classification scheme allows delineation for management recommendations. Patients with multiple small drusen, geographic pigment atrophy or a few larger drusen (>125m) will have the most success when administered the study formulation of antioxidants plus zinc.
AREDS did not consider lutein. Studies of this protein supplement are ongoing (and encouraging), but lutein did not have scientific standing at the inception of AREDS.
Another AREDS shortcoming is that results are not extrapolatable to prevention recommendations. So while it may be intu itive that offspring of AMD patients would benefit, that has yet to be proven. In the meantime, we should recommend that offspring and those at greatest risk for AMD might benefit from a combination of antioxidants and zinc. The study formulation and similar products are available commercially.
The other side of the AMD treatment coin involves choroidal neovascularization. Until recently, subfoveal membranes were not amenable to treatment and those that were had a limited treatment benefit. The introduction of verteporfin (Visudyne, Novartis) provides a larger number of patients with a treatment option.
Practitioners can also help prevent AMD. Discourage smoking and encourage a high-zinc, low-lipid diet. Recommending attenuation of blue light may prevent direct oxidative assault on the macula.
Dr. Semes is an associate professor at the University of Alabama at Birmingham School of Optometry.