Optometrists spearhead the battle to prevent AMD-related vision loss

April 1, 2011

Although exudative disease accounts for 90% of cases of vision loss due to age-related macular degeneration, only 10% of affected patients have exudative form.

"Advanced AMD with either choroidal neovascularization (CNV) or geographic atrophy does not just happen, but rather occurs as a result of a long degenerative process. All cases of advanced AMD started out as dry. Our goals are to stop progression to the stage that can lead to devastating vision loss and improve our early detection of exudative CNV because timely treatment with currently available effective therapies can enhance the patient's visual prognosis and long-term quality of life," said Dr. Pizzimenti, associate professor, Nova Southeastern University College of Optometry, Ft. Lauderdale, FL.

Risk factors, risk reduction

AMD risk factors include modifiable and non-modifiable features. Older age, Caucasian race, heredity/family history, and blue eye color are all associated with AMD. While non-modifiable, these factors can help identify patients at higher risk who may require more aggressive intervention and follow-up.

Smoking, cardiovascular disease, excessive alcohol consumption, certain nutritional deficits, and body mass index above the normal range have also been shown to be AMD risk factors and represent targets for lifestyle and behavioral modifications.

"In the interest of risk reduction for AMD as well as cardiovascular disease, all patients should be encouraged when appropriate to increase their physical activity, maintain a healthy body weight, stop smoking, and avoid excessive alcohol consumption," Dr. Pizzimenti said.

MPOD and PHP assessments

In addition to taking a patient history, measurement of macular pigment optical density (MPOD) offers a simple, non-invasive tool for assessing patient risk and can be used to monitor whether changes in nutritional supplementation and diet are having a desired impact.

MPOD testing is based on heterochromatic flicker photometry and devices are commercially available from two manufacturers (QuantifEye, ZeaVision; MacuScope, Marco). Although normal values are specific to each device, in general, an MPOD score between 0.1 and 0.24 may be considered to be in the low range.

Preferential hyperacuity perimetry (PHP; PreView PHP, Carl Zeiss Meditec) is another tool that optometrists can use for monitoring patients with AMD. This device detects hyperacuity defects associated with conversion from dry to wet AMD and should be performed 2 to 4 times per year in patients with intermediate stage disease in combination with fundus biomicroscopy to look for elevation as a sign of degenerative changes.

"Fluorescein angiography, which determines the integrity of the inner and outer blood-retinal barrier, remains the gold standard for evaluating new onset CNV. However, spectral domain OCT is very useful for identifying membrane leakage and works synergistically with fluorescein angiography and PHP," Dr. Pelino said.

Currently, results of the Age-Related Eye Disease Study1 (AREDS 1) represent the only Level 1 evidence for nutrition recommendations to prevent AMD progression. After 5 years of follow-up in AREDS 1, supplementation with vitamin C 500 mg, vitamin E 400 IU, beta carotene 15 mg, zinc 80mg, and copper 2 mg significantly reduced the risk for progression to advanced AMD in patients with intermediate AMD in one or both eyes, but had no benefit for patients with early AMD or advanced disease in both eyes.