What is AMD?
AMD (Age-related Macular Degeneration) is a term for what was earlier known as calcification of the eye. However, it is not a case of calcified blood vessels (as seen with i.e. legs, heart and brain), which makes the designation inappropriate. Today, AMD is the most frequent cause of loss vision loss and blindness.
AMD is a disease in the retina’s centrum or “the yellow spot” (in Latin: Macula), where the largest concentration of sensory cells is located. These sensory cells, specialised cones, are responsible for our perception of fine details, colours and our three-dimensional sight. The disease is bilateral, meaning, that it is developed on both eyes – but with a difference in extent on the right and left eye.
The cause of the disease is unknown. Research indicates that smoking, heritability, increased blood pressure, and other heart and vascular disorders can lead to an increased risk of AMD.
AMD is the most frequent cause of severe vision loss and blindness in the Western World.
AMD typically strikes people over 50 years of age.
Two types of AMD
It is of great importance to distinguish between two main types of AMD:
The dry form (atrophic), with degeneration of the sensory sells in the yellow spot (macula). Dry AMD is the most common form of AMD as it affects approx. 85-90% of all individuals with AMD.
The wet form (neovascular), with abnormal new blood vessels in the retina, affects approx. 10-15% of individuals with AMD. It often develops in eyes that already suffer from the dry form.
Wet AMD is typically a further development of the dry form, but it can also appear without prior symptoms. The RetinaLyze system solely focuses on locating signs of the dry form, as the system serves as a preliminary screening and over 85% of all AMD cases are dry AMD. Therefore, the rest of this article will focus solely on the dry form of the disease.
One should use amsler's grid test, when screening for wet AMD. Read more here.
What are the symptoms of dry AMD?
Symptoms are rarely evident or noticeable in the early stages of dry AMD. Some patients, however, state that they see a dark spot in the ceiling of their bedroom short after awakening. Light sensitivity can also be a symptom of an incipient disease in the retina. Later, difficulties with reading can occur, as the central field of vision gradually vanishes.
It can be difficult to recognise people in the street, as their face often disappears. This is due to the blind spots in the field of vision caused by damaged or covered tissue in the macula. Gradually, one can loose so much of the sight that driving a vehicle is no longer possible, and optical aids are necessary for reading. The peripheral vision is usually preserved long after the loss of the reading vision. Fortunately, dry AMD develops gradually over a number of years, therefore, not all patient lose their entire central vision.
Symptoms will often occur in one eye only:
Vision impairment that glasses/contact lenses cannot relieve. Mostly experienced on short distance e.g. reading, handwork, or kitchen work.
Blurred central vision – letters “disappear” when reading.
Distorted vision – flagpoles and doorframes look curved and crooked.
Contrasts are less distinct – it is difficult to distinguish between brightness and shadow.
Decreasing of colour sense – it becomes difficult to see the difference between traffic signs.
How is the diagnosis made?
The diagnosis is made by an examination with a so-called ophthalmoscope (equipment that sends light in through the pupil) or through photographing the retina (with a fundus camera) after receiving pupil-dilating drops. An eye specialist can examine the enlarged photos of the retinas with a magnifying glass and look for changes in the retina.
Only eye specialists can make the diagnosis, therefore, regular check-ups at the eye specialist are encouraged, as one grows older. The RetinaLyze system is solely meant as a preliminary screening.
Treatment of AMD
The dry form of AMD cannot be cured, but international studies show that some substances can impede or slow the development of some of the stages of the disease.
In a study from 2001 (AREDS study) it was proven that, in some cases delaying the development by taking supplementation consisting of large doses of vitamins C and E, a preliminary stage to vitamin A (beta-carotene), and the metals zinc and copper.
The eye specialist advises on which patients are suitable. Unfortunately, the treatment only works with a third of the patients.
In case of wet AMD, the development can be slowed down with regular injections of anti-VEGF factors, which are involved in the new development of blood vessels.
Examples of dry AMD (fundus images)
In the picture above, drusen can be seen in and around the macula
In the picture above, drusen can be seen in and around the macula in a myopic patient
Examples of wet AMD (fundus images)
In the image above, drusen in and around the macula can be seen in different sizes as well as elevations around the macula
In the image above, the drusen, larger elevations and scar tissue around the macula are visible
In the image above, the drusen, minor elevations and scar tissue around the macula are visible
In the image above, the drusen, larger elevations and bleeding around the macula are visible