Age-related macular degeneration
It is characterized by degeneration of the ocular macula leading progressively to loss of central vision. In mild cases it may be asymptomatic, but as it progresses it makes it difficult to perform daily tasks due to the associated distortion of vision. It is one of the main causes of vision loss in developed countries, with a worldwide prevalence of around 9% from the age of 45.
There are two primary types of AMD, the dry and the wet form. In the former (80% of cases), yellow deposits, called drusen, form, which when small need not impair vision, but as they increase in size and number, they can obscure or distort your vision.But as they increase in size and number, they may obscure or distort your vision, and as it worsens, lead to loss of central vision. In the wet form (10% of AMD), blood vessels grow under the macula, leak blood and fluid into the retina and can distort vision and cause scarring leading to permanent loss of central vision.
The exact causes that trigger this ocular degeneration are unknown, but in addition to genetic support, the following risk factors may also contribute to its development:
- Age above 50 years, and in 2/3 of the cases it will be women versus 1/3 of males. Similarly, Caucasian ethnicity is the highest risk, followed by Chinese, Hispanic/Latino, and lastly African American.
- Smoking. It has probably been related to the decrease in the amount of oxygen associated with smoking, including the eyes.
- Elevated blood pressure. Probably also related to the oxygen restriction to the ocular system associated with this condition.
- Having heart disease such as angina, stroke, myocardial infarction, is another risk factor for AMD.
- Obesity, high cholesterol levels and diets rich in saturated fats (present 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 the sun's ultraviolet rays.
Three main factors have been described as contributing to AMD: advanced age, environmental factors and genetic factors. In this regard, genetic studies have provided insights into the etiopathological triggering mechanisms, and have allowed determining a contribution of genetic variance close to 50%. The most recent GWAS association studies performed on 67000 samples from the UK Biobank cohort and the FinnGen project on 3700 cases and 205000 controls, have identified up to 10 key loci in the predisposition to this pathology that are involved in variations in retinal thickness.
Symptomatology varies widely among those affected, although it most commonly appears after the age of 55. In addition, in the early stages of AMD, there are usually no symptoms. The most common sign, and one of the first to appear, is the presence of drusen, yellowish deposits in the retina, which are easily identified 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 daily tasks and functions.
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 and 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, manganese. Limiting the intake of saturated fats. The use of supplements with antioxidant vitamins and zinc can contribute to reduce this risk.
- Stop smoking and avoid alcohol intake.
- Protect your eyes with sunglasses to block the harmful effects of ultraviolet (UV) rays.
After the age of 60, it is especially important to visit the ophthalmologist regularly, especially if there is a family history of the disease. Vision tests are essential in the elderly. Vision in both eyes should be checked periodically, with tests as simple as covering one eye and then the other and checking the differences when looking at a distant object, or checking with an Amsler grid.
Preventing the progression of maculopathy, to age-related macular degeneration consists of taking measures to prevent choroidal neovascularization (the growth of new blood vessels in the center of the macula). The only effective preventive measure is smoking cessation, 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 efficacy of antioxidant zinc supplementation 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, despite several clinical studies that vary the protocol slightly, the disappearance of drusen does not reduce the risk of developing choroidal neovascularization.
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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.
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.