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Retinitis pigmentosaRetinitis pigmentosa is not a single disease, but a group of degenerative diseases that affect the eye and are characterized by slow and progressive loss of vision. The most affected part of the eyeball is the retina, which is the layer that covers the inside of the eye and is responsible for acquiring and render images of the outside, turn them into nerve impulses, and send them to the brain via the optic nerve.
Involvement is usually bilateral, so that both eyes are affected. Most frequent symptoms include night blindness, field of view limited loss of peripheral (side) vision and glare. Over time, can cause blindness.
Retinitis pigmentosa may appear as an isolated disease (pigmentary retinitis non syndromic), or be associated with other ocular or systemic pathology (pigmentary retinitis symptoms). In this way, people with retinitis pigmentosa may have other disorders of vision such as myopia, astigmatism, cataract, glaucoma, or alterations of the cornea.
In addition, and although they are rare (represent approximately 15% of all cases), retinitis pigmentosa may be associated with syndromes that also affect other parts of the body. The most frequent are degenerative diseases of the central nervous system (consisting of the brain and spinal cord), muscles, and metabolic disorders. Some of the most frequent associations are called Usher syndrome, where the retinitis pigmentosa appears linked to deafness and Bardet-biedl syndrome, which appears associated with obesity, low IQ, more than five fingers (polydactyly) and small genitals (hypogonadism).
Epidemiology of Retinitis PigmentosaRetinitis pigmentosa is the cause of hereditary of most common retinal degeneration and also the most common cause of blindness of genetic origin in the adult. It is estimated to affect one in 3,700 people, so that around the world there are about 1.5 million people with this disorder. In Spain, more than 15,000 people suffer this ocular pathology, and it is estimated that some 500,000 people are carriers of the altered genes and, therefore, potential transmitters of the disease.
It is slightly more common in men (around 60% of those affected are males) and there seems to be differences between races. Although it is present at birth, it is rare that it occurs before adolescence, making it in a slow, progressive, so it is not discovered until it is quite advanced.
Causes of Retinitis PigmentosaHe retinitis pigmentosa is a genetic disease , and therefore, not it is caused by infections, trauma, injury, or any other external agent. These genetic alterations make the cells of the retina called photoreceptors (cones and rods) work incorrectly, so that over time many of them degenerate and die, thus producing a progressive loss of vision. Other theories suggest that this disease has a cause autoimmune, biochemical or metabolic; However, there is no sufficient evidence showing it.
Retinitis pigmentosa can appear sporadically (in these sporadic cases, which are due to new mutations, sufferers do not transmit the disease to their offspring), or be inherited (hereditary being, tends to affect other members of the same family). Therefore, if disease is diagnosed a person this it is recommended that the members of his family are evaluated by an ophthalmologist. In the hereditary forms we can distinguish three patterns of inheritance:
• Autosomal dominant (one parent is affected and transmitted the disease to half of their children): usually less serious forms, because the disease tends to progress very slowly and the patient retains a good central vision until an advanced age. It affects both men and women.
• Autosomal recessive (parents do not suffer from the disease but are carriers of it, so that 25% of the offspring may be affected): is the most frequent hereditary pattern. The pigmentary retinitis transmitted form of autosomal recessive are more severe than the previous ones and can give symptoms in adolescence (primarily problems of adaptation to darkness).
• Sex-linked inheritance (sons of women who do not suffer from the disease, but are carriers affected): is the form of retinitis pigmentosa, more severe and progressive.
Symptoms of Retinitis PigmentosaRetinitis pigmentosa is a disease whose evolution is slow, chronic and progressive, although frequently occur some spontaneous improvement in acuity and visual field. The most common of retinitis pigmentosa symptoms are as follows:
• Night blindness: while people with normal vision are easily adapted to the darkness after a brief period of time, people with retinitis pigmentosa have an adaptation very slow, so that many times even are not able to correctly distinguish shapes and objects.
• Reduction of the field of vision, usually peripheral vision (what is known as tunnel vision).
• Decrease in visual acuity: usually appear after the above symptoms. It produces difficulty to perceive shapes and objects.
• Glare and flashes (vision of lights): many affected perceived lights or small flashes in the periphery of your visual field that hinder his vision, especially in very light conditions. Light, moreover, is more and more annoying.
• Alteration of the perception of colors: affects especially the blue and yellow, and occurs when the disease is very advanced.
Diagnosis of Retinitis PigmentosaRetinitis pigmentosa It is generally diagnosed in young adults, although certain forms are already evident from early childhood, and others do not manifest themselves until old age. The evolution of the disease is progressive and slow most of the time.
The diagnosis is based on a complete medical history , an examination of the eye (which include study of fundusexamination with a slit lamp and intraocular pressuredetermination), and various complementary tests based on each case (blood analysis, measures of the visual field, of the function of the photoreceptors, visual acuity, pupillary reflexes(, the color vision, etc). The most frequent is to find that the patient present involvement of both eyes, night blindness, reduced visual field and accumulation of pigments in the eye Fund (located mostly in the periphery) was observed. The diagnosis of retinitis pigmentosa is established when it is bilateral involvement (both eyes), loss of peripheral vision and a malfunction of the photoreceptors (observed by alterations in the electroretinogram).
The diagnostic tests that are usually performed in patients in which suspected a retinitis pigmentosa are:
• Study of fundus fluorescein angiography and ophthalmoscopy.
• Study of the visual field (perimetry): allows you to produce a map of the visual field (the area that can be seen), thus providing detailed information about the loss of peripheral vision.
• Study of visual acuity.
• Evidence of adaptation to darkness.
• Sensitivity to the contrast and color recognition.
• Electroretinogram: it is a key test to diagnose the retinitis pigmentosa, since it allows to quantify the response of the photoreceptors (rods and cones) to light. For the realization of an electroretinogram patient sits in a dark room so that your eyes adapt to the dark. Then you cover one eye and the other gets eye drops and a contact lens. Later, electroretinogram machine produces a few flashes and records how to respond to these stimuli photoreceptors. The same process with the other eye is subsequently performed.
• Genetic studies of the affected person and their family members to try to identify the type of transmission and the gene or altered genes.
Treatment of Retinitis PigmentosaRetinitis pigmentosa has not a curative treatment. He is recommended that patients follow a series of General measures such as protect your eyes from the strong sunlight, follow a balanced diet, with adequate intake of vitamins, and a periodical medical control, been doing reviews periodically as deemed necessary.
But each time it has greater knowledge of the genetic alterations and the mechanisms that cause the retinitis pigmentosa, found still a treatment able to effectively stop the degeneration of the retina, or recover lost vision.
Some rare forms of retinitis pigmentosa, which are associated with multi-organ involvement, due to specific nutritional deficiencies and can respond to the modification of diet or vitamin supplementation. The administration of high doses of vitamin A supplements can improve the response of photoreceptors (cones) in the electroretinogram, but there is no evidence that you delay loss of vision. Indeed, administration of high doses of vitamin A in patients with retinitis pigmentosa, is not recommended unless you submit abetalipoproteinemia (the abetalipoproteinemia is a rare disease that affects the gastrointestinal tract and is characterized by the inability of the body to properly absorb fats from the food through the intestine). Also we recommend supplementation of vitamin E, except for patients with retinitis pigmentosa associated with this vitamin deficiency.
The effectiveness in the long term of certain substances such as Docosahexaenoic acid (an omega-3 fatty acid) for the treatment of retinitis pigmentosa is not clearly demonstrated. He is recommended to patients with retinitis pigmentosa consume a diet high in these fatty acids, however, there is no evidence claiming that patients have to consume Docosahexaenoic acid supplementation.
Finally, indicate that they are being currently investigated other possible treatments for retinitis pigmentosa, as gene therapy, which aims to correct the mutations of the defective cells and replace the gene or genes altered by others healthy, transplantation of cells of the retina or prosthesis of Queen electronic (many working groups are researching the development of electronic devices that interact with the visual system healthy parts).