Retinitis pigmentosa is an umbrella term for a group of eye diseases that lead to the destruction of the retina (retina) during its course. The retina is, so to speak, the eyesight-capable layer of our eye, whose destruction leads to loss of vision or blindness. The term "retinitis" is rather misleading because it is not an inflammation of the retina. Correct would be the term "retinopathy", which could not prevail in everyday medical life.
The word "pigmentosa" refers to the pigment deposits on the retina which are typical of this disease and which appear in the ophthalmological examination as small dots.
In Germany, about 30, 000 to 40, 000 suffer from one of the various forms of retinitis pigmentosa. Unfortunately, retinitis pigmentosa is currently not curable and is one of the most common causes of blindness, usually in mid-adult life.
To understand the disease retinitis pigmentosa, it helps to deal with the basic structure and functioning of the eyes.
The human retina represents the light-sensitive layer of the eye. With the help of the rods and cones (light receptors) of which it is composed, the incoming light stimuli can be coded into electrical signals and then transmitted to the brain via further nerve tracts which transmit the light incoming information then processed only to the actual image.
However, the light receptors are not identical everywhere in the eye. The chopsticks, which are located more in the periphery, ie farther out in the field of vision, are important for seeing at night and at dusk, so they can perfectly dissolve contrasts in light and dark, but are not as good in their sharpness as the cones.
The cones, on the other hand, which are mainly centrally located in the retina, are fully used during the day. With the cones, we perceive the colors around us and can see things sharp in the field of vision.
If you take the field of view of both eyes together, you get about an angle of about 180 °. Thus, through the anatomical and functional structure of our eyes, we are able to perceive our surroundings in a "panoramic setting". However, we can only recognize them sharply in the focus of our field of view, the area in which the incoming image intersects from the left and from the right. Here we can discern even small details sharply, whereas we further outside (thus further peripheral), the areas rather to the unconsciously running orientation use.
If our eyes are fully functional, it does not pose a problem for us to take a closer look at a certain, more distant object, such as a road sign, and at the same time perceive the surrounding environment, such as an approaching car.
As already mentioned, retinitis pigmentosa is essentially a collective term for a large number of diseases in which similar processes take place. The classification is sometimes different in different works of the literature, but in principle one can distinguish between three groups of retinitis pigmentosa:
In addition to these three basic forms, there are other forms of retinitis pigmentosa, which can not be clearly assigned to one of these groups. These include the extremely rare treatable forms of retinitis pigmentosa: Atrophia gyrata, Basse-Kornzwei syndrome (also known as abetalipoproteinemia ), and Refsum syndrome. Here a good cooperation with a metabolic and a nutritional specialist in the foreground in order to be able to get the disease under control.
The symptoms and processes in the eye treated so far are primary retinitis pigmentosa, affecting 90% of those affected. The exact genetic causes that underlie this disease have not yet been sufficiently researched. Until now, it could only be stated that there are various changes in the genetic make-up and various protein defects in those affected. So it happens that the course of the disease can be individually quite different, only the final stage with the complete loss of retinal photoreceptors is identical in all.
If the retinitis pigmentosa does not appear alone, but patients still suffer from other symptoms that have nothing to do with the eye, it is an Associated Retinitis Pigmentosa, usually as a partial symptom of a syndrome.
Common comorbidities may include: hearing problems, muscle weakness to muscle paralysis, gait disturbance, growth disorders, problems with severe scaling and photosensitivity, mental retardation, congenital cystic kidney and / or heart malformations and cardiac arrhythmias.
The two most common syndromes are Usher syndrome and Bardet-Biedl syndrome.
A pseudo-retinitis pigmentosa or phenocopy, on the other hand, is said to be the case if the patients have the described typical symptoms of a primary retinitis pigmentosa, but no hereditary components are identified, but the destruction of the retinal cells was caused by other diseases.
This can for example be the case with autoimmune diseases, inflammation or poisoning (by poisons or by drugs or other substances).
The characteristic symptoms that occur include:
The severity and severity, as well as the order in which the symptoms occur, can be different for each.
In retinitis pigmentosa, the visual field gradually diminishes due to the destruction of the visual cells. Typically, it narrows more and more from the peripheral areas, until only a very small amount of visual cells is preserved at the very center. This is commonly referred to as "tunnel vision" or "tube visual field". The name alone also shows the unaffected person quite well how to imagine this form of limited vision.
The visual acuity, on the other hand, can still be reasonably well preserved, so that there are those who need aids such as a blind rod in order to cope in everyday life, but are nevertheless able to read a newspaper or a book.
Unfortunately, this combination often leads, in healthy people, to believe that retinitis pigmentosa patients only simulate their visual impairment.
Not infrequently it happens that the affected person becomes aware of the limitations of the visual field only after an incident or even an accident, since the brain is very well able to compensate for failures in the field of vision and to calculate a good image of the environment.
In some patients with retinitis pigmentosa, however, the failures also manifest themselves quite differently, for example as a circular ring around the focal point (a so-called ring-shaped scotoma) or as differently distributed black spots.
Rarely, but in principle also possible, is a beginning of the field defects in the center, at the site of the macula (place of the sharpest vision in the retina). Affected then need very early on aids such as magnifying glasses and the like to be able to see objects sharply, while the orientation in the room is still relatively well preserved.
Because retinitis pigmentosa affects the rods before the cones, the symptom of night blindness appears much earlier than the visual field defects. This means for the sufferer that he is almost blind at night and relies on help, while he does not notice any major restrictions in sufficient light.
As soon as the cones are attacked in the further course, it comes to the described failures in the field of vision and to increased photosensitivity, the patients are quickly blinded and darker parts of the image are outshined by brighter. This is because contrast perception in the human eye only comes about through the interaction of neighboring cones. However, if these are damaged, not only the color perception is impaired, but also the contrast perception.
This symptom is further aggravated by the green cataract, which often occurs in patients suffering from retinitis pigmentosa. It comes to a clouding of the lens, which then can no longer properly bundle the incoming light but rather scattered, which still promotes the glare effect.
To date, there is no possibility of curing retinitis pigmentosa. Some studies indicate a slightly slower course of the disease when taking vitamin A. Others consider hyperbaric oxygen therapy to be helpful.
So far, only in research and not yet tested are gene therapy approaches and stem cell therapies that try to attack the disease by its cause, the defective genes.
Also in discussion are retinal implants intended to serve as a prosthesis.
In people who suffer from retinitis pigmentosa, many of the functions of the eye or retina described above are no longer possible due to the destruction of rods and cones. The light receptors gradually die as part of the disease, with usually the rods and later only the pins are affected.
Depending on where the decline of the receptors is the strongest, it can lead to different failures of the visual field and different functional failures.
In most cases, the cause of retinal pigmentosa is a hereditary or spontaneous mutation of certain genes, which leads to a degeneration of the retina or the rods and cones.
If the retinitis pigmentosa is not based on a hereditary component, it is also called a pseudo retinitis pigmentosa, in which case the cells are also destroyed. The trigger here are, for example, autoimmune diseases or inflammatory events.