Macular degeneration

Macula (yellow spot) is an area located in the retina and measures about five millimeters in diameter. It contains important photoreceptor cells of the eye, whose task is normal vision, as well as sharp vision (for example, the letters in reading).

The macula region contains millions of photoreceptors (cones), which are important for colour vision. The rest of the retina contains mainly rods, whose job is to see blurred black and white images. These can be seen even in dim light.

In older people, age-related macular degeneration (AMD) is the most common cause of severe visual impairment and blindness in the elderly group in industrialized countries. Mainly people over the age of 65 are affected by this eye disease.

In the course of macular degeneration, the cells of the retina in the area of the yellow spot (the area with the highest number of photoreceptors) die off. As a result, vision in the centre of the field of vision is reduced, making it increasingly difficult to read and recognise faces. In contrast, orientation in space is still possible without hindrance, as the ability to see outside the centre is not impaired.

One can distinguish between two forms of age-related macular degeneration:

• Dry form of macular degeneration

This form of macular degeneration affects the majority of patients. It progresses slowly, which is why vision is only slightly affected for a long time. However, the dry form can change into the wet form of macular degeneration.

• Wet form of macular degeneration

The wet form of macular degeneration affects only 10 to 15 percent of patients. It is the cause of severe visual impairment. In contrast to the dry form of macular degeneration, the wet form can progress very quickly because pathologically altered blood vessels grow in the area of the macula. As a result, blood and fluid leak from these blood vessels into the surrounding retinal tissue.

In age-related macular degeneration, only one eye is affected at first. However, in about 50 percent of those affected, macular degeneration also develops in the other eye within five years.

The main reason for macular degeneration (both dry and wet) is old age. Especially people from the age of 65 are affected.

The macula is the place with the highest density of photoreceptors. For this reason, a particularly large number of degradation products of the visual process accumulate here. These degradation products are deposited as colour pigments (lipofuscin) in the retina.

Nevertheless, other factors such as smoking, high blood pressure or a familial (hereditary) disposition can play a role in the development of macular degeneration.

So far, however, it is still unclear what is the reason for the formation of new blood vessels in wet macular degeneration.

The first sign of macular degeneration is reduced visual acuity, for example when reading:

• Straight lines, such as a window frame, appear bent. In this case, one speaks of "distorted vision" (methamorphosis).
• In the case of macular degeneration, those affected see blurred and distorted in the centre. In some cases, a dark spot may also appear at this point.

Because of these vision problems, patients are unable to perform certain activities, such as reading or driving.

Macular degeneration can be diagnosed by the following methods:

• Examination of the back of the eye with an ophthalmoscope or a magnifying glass and light source (opthalmoscopy).
• Examination with visual signs on an eye chart and the so-called Amsler grid: This refers to a grid with a black dot in the center. People suffering from macular degeneration can no longer see the grid around the dot sharply while the dot is fixed.
• Dye examination (fluorescence angiography) for wet macular degeneration: In this procedure, the doctor injects a fluorescent dye into the vein in the arm and uses a camera to monitor its distribution in the retina. The type of therapy is then determined by the results of the examination.
• Sometimes it may also be necessary to perform an electrophysiological examination of the eye (electroretinogram). Its purpose is to control the progression of macular degeneration and to exclude other eye diseases.

Dry Degeneration:

Effective treatment options are available to patients with dry age-related macular degeneration only under certain circumstances. Rheophoresis is one therapeutic option. In this procedure certain proteins are removed from the blood. Rheophoresis is similar to dialysis in its properties and leads to an improvement in the flow properties of the blood. However, the benefit of rheophoresis for patients with macular degeneration is not yet proven. In addition, the use of visual aids (such as an illuminated reading magnifier or a screen reader) is the only efficient way to improve vision. Reading books in large print also provides relief. As a general rule, people suffering from macular degeneration should not smoke.

Wet degeneration:

In 10 to 20 percent of those affected with wet age-related macular degeneration, laser treatment promises a good chance of recovery. With this method, the high-energy laser beams obliterate the pathological new vessels. However, this is only possible for vessels that are not located directly in the macula. Another disadvantage is that in the course of the treatment, scars can develop even in the intact tissue, leading to impaired vision.

In photodynamic therapy, the doctor injects a harmless dye into the vein in the arm, which then accumulates in the diseased vessels, making them vulnerable to low-energy laser light. With this procedure, the vessels are targeted without affecting the surrounding healthy tissue.

Another treatment method for macular degeneration is the use of drugs containing antibodies (e.g. pegaptanib and ranibizumab). These drugs exert their effect on the growth factor VEGF ("vascular endothelial growth factor"). VEGF supports the formation of new blood vessels in the eye, which triggers wet macular degeneration. The substance containing the antibody is administered directly into the vitreous body of the eye.

The use of surgical methods, such as subretinal surgery, is only used in the more advanced form of wet macular degeneration. This operation usually does not lead to an improvement of visual acuity, but only to a stabilization of the course of the disease. Another method is the retinal rotation (retinal rotation) with relocation of the macula. However, this method has not yet been clinically proven, which is why it is not routinely used.

The macular degeneration is one of the progressive diseases, about which no clear prognosis can be made. It is also impossible to predict how quickly this process will progress. In many cases it can come to a delayed course, if the macular degeneration is treated in time.

In the course of a macular degeneration it usually does not come to a complete blindness. Orientation in space is still possible. However, the ability to read is lost as time goes on.