The disease known as retinitis or retinitis pigmentosa is, in fact, a group of pathologies that have in common a genetic alteration that modifies the reception of light in the retina. The cells of the fundus of the eye progressively degenerate as the pathology progresses.
It is a rare disorder, with a frequency of 1 patient every 3,000 people. In any case, if we consider all the dystrophies that are transmitted from parents to children, it is the most common of that group. What are your causes? Below, we detail everything about it.
Causes of retinitis pigmentosa
This disease is genetic and hereditary; that is, parents, transmit it to their children due to a mutation in the genes. We say it is a group of disorders and not just one because thousands of changes in DNA (deoxyribonucleic acid) have been identified that culminate in retinitis pigmentosa.
Still, in a third of those affected, it is impossible to find the origin of the disease. Although it is still maintained that it is a genetic cause, in them, it is not possible to reach the mutation that degenerates the cells.
Due to this variability, its inheritance has been classified into three groups:
- By the X chromosome: in these cases, it is only the men who suffer the symptoms, while the women act as carriers, without developing the pathology at any time, although they do pass it on to their male children.
- Dominant: A dominant transmission of a gene means that it is always expressed. In retinitis pigmentosa of this type, all generations of the same family with the mutation have vision loss.
- Recessive: unlike the previous one, the recessive transmission does not always appear, so parents may have symptoms, while children do not, and then grandchildren do.
Symptoms of the disorder
The disease, despite responding to different mutations, coincides in some symptoms that are general for all patients. The age of appearance of the first signs is usually adolescence.
The progression of retinitis pigmentosa leads to a gradual loss of vision. However, it is not always the same. The most frequent forms of presentation are as follows:
- Color confusion: similar to color blindness, patients confuse one color with another or do not identify it as such.
- Loss of central vision: central vision is the one we use most for tasks that require concentration at close range. If the patient loses this ability, reading becomes difficult, for example. This has to do with the area of the retina that suffers from the disorder in the first place. Consultation for this symptom can be confused with farsightedness, especially if the person is over 40 years old.
- Tunnel vision: this is the reverse of the previous process. The patient loses the ability to distinguish shapes and colours at the periphery of his visual field, so only what is in the centre and at a short distance is clear. The name “tunnel” has to do with the sensation experienced by those who suffer from it. It is not unique to retinitis pigmentosa and, therefore, it can also be confused with other pathologies.
- Decreased ability to see in the dark: this is one of the most frequent presentations and one that most guides the diagnosis. It means that the patient normally sees during the day, but when the light darkens or goes out in an environment, it tends to almost absolute blindness.
How is it diagnosed?
The first is the suspicion of retinitis pigmentosa. If it is a person who has a family history, then the doctor will have a hypothesis from the first moment. But if there are no previous records between parents or grandparents, the task is much more difficult.
Once symptoms are established, a genetic test is usually requested. Through a blood sample, the composition of genesis analyzed to locate those that are defective, and that could explain the disorder.
The evaluation can be complemented with electroretinography, which is the measurement of the electrical activity of the retina, and with an optical coherence tomography. The latter is a series of images that are obtained from the retinal tissue in high definition.
The visual field is a test that is always performed in ophthalmology and does not contribute to the diagnosis. It is useful to establish the degree of involvement of the patient since it is possible to know how much the progression has evolved based on the remaining visual capacity.
Treatment of retinitis pigmentosa
There is no cure for retinitis pigmentosa. What is done is to try to reduce symptoms and slow the progression of blindness to improve the quality of life of the affected person.
Some experimentation with high doses of vitamin A in the chemical form of palmitate was successful. However, it is not clear that this is a treatment of choice, nor that the adverse effects of these concentrations do not represent a risk in other organs, such as the liver.
Anti-inflammatory drops are also prescribed if there are bothersome symptoms, such as itching, pain, the feeling of eye grit, or redness. These drugs are for relief only but are by no means chronic options.
Surgery is used in very specific cases. If cataracts accompany the disease, then it can be operated. Besides, the artificial retina implant is still being studied to determine how effective it is.
The importance of prenatal consultation
As it is an inherited disease, prenatal consultation in retinitis pigmentosa is basic. Who wants to have children and already has a diagnosis of the pathology, should be advised on how to proceed. There is no way to avoid it, but precautions must be taken.
In the case of presenting ocular symptoms or perceiving that vision is failing, the consultation should be prioritized. The ophthalmologist will know how to perform complementary methods to address the problem.