Age-related macular degeneration

It is characterized by the degeneration of the macula, which progressively leads to the loss of central vision. In mild cases, it may be asymptomatic, but as it progresses, it makes daily tasks difficult due to the associated vision distortion. It is one of the main causes of vision loss in developed countries, with a global prevalence of around 9% from the age of 45.

There are two primary types of AMD: dry and wet. In the first (80% of cases), yellow deposits called drusen form. When small, they may not affect vision, but as they increase in size and number, they can darken or distort your vision, and as it worsens, cause the loss of central vision. In the wet form (10% of AMD), blood vessels grow under the macula, leaking blood and fluid into the retina, which can distort vision and create scars that cause permanent loss of central vision.

The exact causes triggering this ocular degeneration are unknown, but besides genetic predisposition, the following risk factors also contribute to its development:

  • Age over 50 years, with 2/3 of cases being women compared to 1/3 of men. Similarly, Caucasians are at the highest risk, followed by Chinese, Hispanic/Latino, and lastly African American.
  • Smoking. It is likely related to the decreased amount of oxygen associated with tobacco consumption, including the eyes.
  • High blood pressure. Probably also related to the restriction of oxygen to the ocular system associated with this condition.
  • Having heart disease such as angina, stroke, or myocardial infarction is another risk factor for AMD.
  • Obesity, high cholesterol levels, and diets rich in saturated fats (found in foods such as meat, butter, and cheese) as well as alcohol intake would increase the risk of developing AMD.
  • Prolonged sun exposure due to the effect of ultraviolet rays.

Symptoms

The symptoms vary widely among those affected, although the most common is that it appears after the age of 55. In addition, it is common that in the early stages of AMD, no symptoms are present. The most common sign, and one of the first to appear, is the presence of drusen, yellowish deposits in the retina, which are easily identifiable by an ophthalmologist. As the pathology progresses, the following symptoms may also appear:

  • Blurred or fuzzy vision, difficulty recognizing familiar faces.
  • Distortion of straight lines, a dark and empty area or a blind spot appears in the center of vision.
  • Loss of central vision, necessary for everyday tasks and functions.

Prevention

There is no preventive treatment as such, but there are recommendations that can delay the development of the disease or slow its progression:

  • Eat healthy, including dark green leafy vegetables (such as spinach), fish as a source of omega-3 fatty acids, and antioxidant vitamins A, C, and E, lutein, and zeaxanthin, and minerals such as copper, zinc, magnesium, and manganese. Limit the intake of saturated fats. The use of supplements with antioxidant vitamins and zinc can help reduce this risk.
  • Quit smoking and avoid alcohol consumption.
  • Protect the eyes with sunglasses to block the harmful effects of ultraviolet (UV) rays.

From the age of 60, it is especially relevant to visit an ophthalmologist regularly, especially if there is a family history of the disease. Vision tests are essential in older people. Vision in both eyes should be checked periodically with simple tests such as covering one eye and then the other and checking for differences when looking at a distant object, or checking with an Amsler grid.

Preventing the progression of maculopathy, to age-related macular degeneration, involves taking measures to prevent choroidal neovascularization (the growth of new blood vessels in the center of the macula). The only effective preventive measure is to stop smoking, as the use of antioxidants such as beta-carotene, vitamin C, tocopherol, or zinc has not been shown to have a preventive effect. Once maculopathy is established, the effectiveness of antioxidant zinc supplements has not been demonstrated. It has been clinically observed that laser photocoagulation of drusen (yellow deposits under the retina) leads to their disappearance and the retina regains an almost normal appearance. Unfortunately, and despite various clinical studies carried out that slightly vary the protocol, the disappearance of drusen does not reduce the risk of developing choroidal neovascularization.

Number of observed variants

13.5 million variants

Number of risk loci

9 loci

Genes analyzed

ARMS2 C3 CFH CFHR3 FAAP100 HTR5A PILRA RDH5 SKIV2L

Bibliography

Saunier V et al. Incidence of and Risk Factors Associated With Age-Related Macular Degeneration: Four-Year Follow-up From the ALIENOR Study. JAMA Ophthalmol 2018;136(5):473–481.

National Institute of Health-National Eye Institute. Age-Related Macular Degeneration [March 2022].

American Academy of Ophtalmology. [March 2022].

Johns Hopkins Medicine Institute. [March 2022].

Kaye RA et al. Macular thickness varies with age-related macular degeneration genetic risk variants in the UK Biobank cohort. Sci Rep. 2021;11(1):23255.

FinnGen. FinnGen Documentation of R5 release 2021 [2022/02].

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