Age-Related Macular Degeneration
In addition to a dilated retinal examination and digital color photography, various retinal imaging tests may be utilized to further assess the AMD.
Fluorescein Angiography is an office-based test that can aid in determining the extent of macular degeneration and distinguishing between dry and wet AMD. Fluorescein angiography is performed by injecting sodium fluorescein dye into a peripheral vein in the arm with a small needle. This dye travels through the blood vessels of the body and eyes. Choroidal neovascularization in the macula can be visualized as a leaking blood vessel complex under the retina. It is regarded as a safe test, but people should expect some temporary and mild yellowish discoloration of the skin and urine. Most people have no difficulty with this testing, although a small percentage of people will experience some transient nausea. Any angiogram test, however, can rarely be associated with allergic or even more severe reactions, and therefore this test is typically reserved for people in whom wet AMD is noted or suspected.
Optical Coherence Tomography (OCT) is a non-invasive, office-based imaging test that uses a special light to scan the macula and determine whether there is fluid in the macula, potentially signifying wet AMD. It is commonly used in combination with fluorescein angiography to help diagnose wet AMD and is also used to monitor the response to treatment for wet AMD. There are no side effects or risks involved with OCT; there is no radiation involved.
Autofluorescence is another non-invasive imaging test is useful for evaluating the health of the pigmented cell layer beneath the macula in those who have dry AMD. The pigmented cell layer plays an important role in sustaining the health and function of retinal photoreceptor cells. Specifically, it is used to identify and track progression of geographic atrophy, which involves the loss of this pigmented cell layer and in turn, the loss of photoreceptor cells.
Most people with AMD will retain good central vision and the ability to read in their lifetime. This is because 90% of people have dry AMD. This is often associated with a more favorable prognosis compared to wet AMD, though dry AMD may also gradually progress to an advanced form with atrophy of the macula, limiting central vision. People with wet AMD will quickly suffer central vision loss if left untreated. While patients may progress to legal blindness, it is important to realize that AMD affects central vision - it typically does not lead to total loss of vision. Thankfully, there are new treatments available for those with wet AMD.
Dry AMD - There is no treatment available yet that can either halt the progression or recover vision loss from dry AMD. However, the Age Related Eye Disease Study (AREDS), sponsored by the National Eye Institute (NEI) of the National Institutes of Health (NIH), showed that a specific formulation of antioxidant vitamins and minerals had a clinically proven benefit in reducing the risk of progression of dry AMD to more advanced stages and associated vision loss by 25%. In May of 2013, the NEI proposed a modification to the original AREDS formula based on the AREDS2 study, which was an update to the original AREDS clinical trial. The AREDS2 formula contains:
- 500 mg Vitamin C
- 400 IU Vitamin E
- 10 mg Lutein
- 2 mg Zeaxanthin
- 80 mg Zinc oxide
- 2 mg Copper oxide
It is prudent to check with your primary care physician before starting this micronutrient supplement. In general, Vitamin E supplementation should not exceed 400 IU. In addition, unlike the original AREDS formula, there is no beta-carotene in the newer AREDS2 formulation (it was replaced by lutein and zeaxanthin). This is significant because some studies in the medical literature have identified increased rates of lung cancer with high levels of beta-carotene in heavy smokers.
Based on epidemiologic studies, certain lifestyle and nutritional changes may be beneficial. Based on what is known to date, the following recommendations may be made in hopes of improving the prognosis of dry AMD:
- Stop smoking. Smoking has been associated with vision loss and more advanced forms of AMD.
- Eat a diet rich in colorful vegetables and fruits. These food groups have been associated with lower rates of progression to advanced AMD and contain anti-oxidants (eg. lutein) which may slow progression of disease.
- Control blood pressure. High blood pressure is associated with more advanced AMD.
- Be physically active. People with AMD who are physically active several times a week may reduce their risk for progression to advanced AMD and vision loss.
- Consider eating food rich in Omega 3 fatty acids. Omega 3 fatty acids are found in cold water fish such as tuna and salmon along with nuts. Studies show that a diet with high omega 3 fatty acid intake is associated with less advanced AMD.
Wet AMD - In that past, laser-based therapies were used to target the abnormal blood vessels that cause wet AMD. However, the laser burns typically resulted in scarring and damage to central vision. Fortunately, there are now anti-vascular endothelial growth factor (anti-VEGF) medications available for the treatment of wet AMD. These medications, injected into the eye as an office-based procedure, are currently the preferred therapy for wet AMD due to their unprecedented efficacy. They represent the first therapy that has ever been clinically proven to help improve vision in a substantial proportion of patients with wet AMD. Timing is important, as earlier identification and treatment of wet AMD is associated with better visual outcomes.