Age-Related Macular Degeneration: Symptoms, Causes and Treatment

Age-related macular degeneration, AMD or ARMD, is a degenerative retinal disease primarily affecting those over the age of 55. Specifically, it affects the macular region of the retina, which is responsible for our sharpest central vision.

In industrialized countries, AMD is the leading cause of blindness. In 2020, there were an estimated 196 million people living with this condition worldwide. This is expected to increase to 288 million by 2040.

There are two types of AMD: dry and wet.

Dry AMD is the most common, making up approximately 90% of all cases. Mild or moderate dry AMD has less of an impact on vision. However, late dry AMD, also called atrophic AMD, can be visually devastating.

Wet AMD involves neovascularization, or new blood vessel growth. These blood vessels are fragile and leak, causing fluid to accumulate in the macula. Like atrophic AMD, wet AMD can cause profound visual changes.

AMD symptoms

Dry AMD tends to progress relatively slowly. Early AMD may not cause much visual change. It is sometimes uncovered on routine dilated eye examinations.

Moderate AMD may cause some decline in central vision. Vision may seem blurry, even with glasses on. Straight lines may appear wavy. In an eye exam, an Amsler grid is sometimes used to test vision in macular degeneration. The Amsler grid is made up of a series of criss-cross lines. While you view a central target, you’re asked to report whether any of the lines appear wavy. You can also monitor their vision at home this way. The Amsler grid can be kept on the refrigerator for easy access. Vision should always be checked one eye at a time.

Late dry AMD, sometimes called geographic atrophy, can cause missing areas of central vision. Faces can become difficult to recognize.

Dry AMD can convert to wet AMD with the development of new blood vessel growth. Wet AMD tends to come on somewhat suddenly, causing a decline in visual clarity.

Causes

Macular degeneration has a variety of causes. Risk factors include age, genetics, and environmental factors such as diet and smoking.

Advancing age is the main risk factor for AMD. Prevalence of early AMD is 3.5% in those aged 55-59, as compared to 16.7% in those aged 85 and older.

Genetics play a strong role in AMD risk. Various genes have been identified, with some increasing risk and others decreasing risk. If you have a family history of macular degeneration, make sure to make your eye doctor aware.

Smoking increases the risk of AMD by 2-4 times. It is the most consistently reported modifiable risk factor. Several studies show that the more a person smokes, the higher their risk of AMD. Quitting smoking reduces risk; in fact, 20 years after quitting, the risk of AMD returns to a level comparable to that of a non-smoker.

Diet. Eating specific fruits and vegetables rich in certain antioxidants may have a protective role against AMD. Carotenoids like lutein and zeaxanthin have been found to be especially beneficial. These can be found in dark leafy greens and yellow/orange vegetables and fruits.

Treatments

The treatment used for AMD depends on the stage and type of disease. Treatments are currently available for moderate dry AMD and wet AMD.

Moderate Dry AMD: The Age-Related Eye Disease Study 2 (AREDS 2) found that a certain combination of antioxidant vitamins and minerals can slow the progression of moderate dry AMD. These supplement formulations can be obtained over-the-counter.

Wet AMD: The main treatment used for wet AMD is anti-VEGF injections. VEGF stands for vascular endothelial growth factor. VEGF promotes leakage and bleeding from the blood vessels inside the eye. Therefore, anti-VEGF inhibits this process. Anti-VEGF injections are given in the affected eye(s). They only work for a limited period of time, so injections must be repeated on a regular basis. The goal is to stop the fluid buildup from the leaking blood vessels, in an attempt to improve vision.

Key take-aways

Macular degeneration is a condition that involves a deterioration of the macular tissue. There are two types of AMD: dry and wet.

AMD impacts the central vision, causing blurry and distorted vision. Sometimes, areas of central vision may be missing, making it difficult to recognize faces.

There are several risk factors that have been identified for AMD, including age, genetics, and lifestyle. Although there are treatments available for certain types of AMD, the condition is not curable.

Supplements can slow the progression of dry AMD, while anti-VEGF injections can keep wet AMD under control.

Those with macular degeneration should monitor their vision at home, one eye at a time, using an Amsler grid in between appointments. Any changes should be reported to an eye care professional.

Although vision can be impacted to varying degrees in macular degeneration, it can often be optimized through the use of glasses, magnifiers, or other visual aids.

References

Dry vs Wet Age-Related Macular Degeneration. [online] American Macular Degeneration Foundation. Available at: https://www.macular.org/about-macular-degeneration/what-is-macular-degeneration/types/dry-vs-wet-macular-degeneration

Heesterbeek TJ, Lorés-Motta L, Hoyng CB, Lechanteur YTE, den Hollander AI. Risk factors for progression of age-related macular degeneration. Ophthalmic Physiol Opt. 2020;40(2):140-170. doi:10.1111/opo.12675

Keenan TDL, Cukras CA, Chew EY. Age-Related Macular Degeneration: Epidemiology and Clinical Aspects. Adv Exp Med Biol. 2021;1256:1-31. doi:10.1007/978-3-030-66014-7_1

Mukamal, R., 2021. Genetics and Age-Related Macular Degeneration [online] American Academy of Ophthalmology. Available at: https://www.aao.org/eye-health/diseases/age-related-macular-degeneration-amd-genetics

Thomas CJ, Mirza RG, Gill MK. Age-Related Macular Degeneration. Med Clin North Am. 2021;105(3):473-491. doi:10.1016/j.mcna.2021.01.003

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