Age-related macular degeneration (AMD) is a disease associated with degenerative changes in the retina that cause a gradual loss of central vision. It is observed quite often in people over 55 years old. Sometimes similar changes occur at a younger age.
A macula is a small area in the center of the retina where a person’s visual acuity is greatest. It has an oval shape and is located against the pupil. Sensitive cells in it – photoreceptors – convert the light of the visible region into electrical signals and transmit them through the optic nerve to the brain. With AMD, these cells begin to degenerate and stop performing their function.
People at the first stage of AMD notice “blurring” of central vision, especially during reading or other activity that requires eye strain. It becomes difficult to distinguish between small details and to read. In addition, straight lines in the field of view begin to distort or deform. As the disease progresses, “blind spots” begin to form in the central vision zone, and visual acuity decreases significantly.
As a rule, the disease first develops in one eye, but then the second eye is always affected. The degree of central vision loss depends on the type of AMD – dry or wet.
The dry type of macular degeneration is the most common (90% of all cases) and usually affects vision less than the wet type. It is characterized by the appearance of druses, small yellowish-white spots containing proteins and fats that are deposited on a thin layer of cells under the photoreceptors on the retina. The origin of the drusen is not exactly known, but it may be a waste product of the retinal tissue. Drusen can affect the macula, causing gradual degeneration of photoreceptors. However, sometimes they can exist without affecting the quality of vision.
Decreased vision with dry AMD occurs gradually over several years and is relatively easy to tolerate. Vision may even remain stable for a while. People with dry AMD do not usually lose their eyesight completely; it is just that tasks that require focusing their vision become more and more difficult for them to perform.
According to recent studies, the presence of moderate to large drusen is a risk of transition from dry AMD to wet AMD, which is the cause of significantly greater vision loss.
To date, there is no standard therapy to treat dry AMD, but research is underway on new methods, such as the use of a laser, to reduce its size.
Wet AMD accounts for approximately 10% of all cases of macular degeneration. It is caused by blood vessels starting to grow in the retina. This condition is characterized by hemorrhages, which leads to irreversible damage to the macular region with the formation of white spots and loss of central vision. Wet-type degeneration is more rapid and severe, and accounts for most cases of blindness from this disease.
Drug therapy for people who are at risk of developing wet AMD is based on the use of drugs and vitamin complexes, which include the antioxidants beta-carotene, vitamin E and vitamin C, as well as supplements containing zinc and copper.
There are also several types of drugs that reduce the formation of blood vessels in the retina and thus reduce the risk of vision loss from AMD. Usually, these medications are administered by injecting it into the eye at regular intervals. According to clinical studies, the majority of patients using such drugs did not experience any serious deterioration in visual acuity.
Another method is photodynamic therapy using a light-sensitive drug that is injected into the bloodstream intravenously. Then, when the drug reaches the eye, the affected areas on the back of the eye are illuminated with a low-power laser, which activates the drug that destroys unhealthy vessels in the retina. The procedure is very short and painless and must be repeated several times. This treatment can be combined with another.
Recently, a new direction of treatment has been developing, when a miniature telescope (objective) is implanted in the eye instead of the lens to improve central vision. This method is most suitable for patients with advanced AMD. This device enlarges the object in the center of vision to the size of the entire retina, thus using other healthy areas. The telescope is always used on one eye as the other provides peripheral vision. In the process of adapting to the device, the brain “learns” to combine images from two eyes into a single image.
Some recent developments do not use a lens, but a camera built into, for example, glasses, which captures images of an ever-changing environment and transmits a signal to an epiretinal implant with multiple electrodes on the retina that act as dead photoreceptors. The technology is designed specifically for people who have intact retinal neurons that can be electrically activated.
All of these treatments have received approval from the FDA (U.S. Food and Drug Administration).
New treatments for AMD, which are currently undergoing clinical trials, are based on the latest advances in science. For example, they currently test technology that uses embryonic stem cells to treat degenerative eye diseases (dry AMD). In this treatment, patients are implanted with cells of the retinal pigment epithelium, which were obtained from stem cells, which will not only slow down the development of the disease but also, possibly, restore vision. In addition, other areas of research should be mentioned:
In studies conducted in 2006, it was found that 74% of AMD cases have changes in the CFN gene, as well as in the BF and C2 genes. Although the influence of genetics and the environment on AMD is still not fully understood, this finding has confirmed the effect of genetic changes on this disease. These genes are an obvious target for the development of new effective therapies. At the same time, it is quite possible that changes in other genes also affect the occurrence of AMD, which may be discovered later.
The causes of age-related macular degeneration have not yet been determined. However, risk factors today include genetics, diet, smoking, exposure to sunlight, cardiovascular disease and hypertension.
In more than half of the cases of AMD, according to research, one of the main factors is genetics. In particular, the CFN gene (Complement Factor H) is associated with this disease, which is associated with at least 50% of cases of macular degeneration. In addition, scientists have found other genes associated with AMD, albeit in fewer cases.
The best way to detect changes is to self-test at home using the Amsler grid. This is a grid of lines intersecting at right angles, similar to a regular page from a checkered notebook. It can be easily found on the Internet along with instructions for use and printed. Each eye should be checked separately while wearing your reading glasses. You need to focus on a point in the middle of the grid and if the lines look wavy or blurry, see your doctor right away.
If central vision begins to deteriorate, then you can use the following means: a magnifying glass or special lenses, a screen to enlarge small text, software that translates text into speech and vice versa, etc. Experts with the same problem can adapt to normal household activities for visually impaired people – such people can possibly be found with the help of specialists from an ophthalmological center.