Horoideremiya is a hereditary dystrophy of a vascular cover of an eye of which damage of a retina, a pigmentary epithelium and photoreceptors is characteristic. The clinical picture is presented by violation of twilight sight, feeling of a foreign matter in eyes, a headache. Progressing of a disease leads to an amavroz. Diagnostics is based on carrying out an oftalmoskopiya, perimetry, a vizometriya, elektroretinografiya, retina angiography. Etiotropny therapy is not developed. Symptomatic treatment comes down to application of hypotensive means, vasoprotectives, fermental medicines, vitamins of group C, B, A and PP.
Horoideremiya (tapetokhorioidalny dystrophy, horiodermiya) – rare genetic pathology. Prevalence of a disease in Sal's community in the north of Finland makes 1:40. In other regions the disease meets much less often – 1 case on 50 000 people. Only men as the disease is inherited on the H-linked recessive type are ill a horoideremiya. At women, being carriers of a pathological gene, minor changes of a vascular cover of eyes can be defined. At 87% of patients the first symptoms of a disease arise at early children's age and only at 13% – in teenage. In 37% of cases by 50-60 years visual acuity decreases up to a svetovospriyatiya.
The etiology of a disease is connected with CHM gene mutation. The child inherits a defective gene from mother carrier. The disease develops at all boys in a family and males in the area of mother. As female persons have two H-chromosomes, changes of structures of a uvealny path at them are expressed slightly. The causes of mutations at the gene level are up to the end not found out. Scientists believe that their emergence is promoted by influence of adverse factors of the external environment (ultra-violet radiation, reception of medicines during pregnancy). In too time, cases of spontaneous mutations are widespread.
In the mechanism of development of a disease the leading value is allocated for a genetic mutation. Type of inheritance of pathology – H-linked recessive. The mutated gene of CHM includes 15 ekzon on the site of 15 kb of a chromosome of Xq2l.2. Scientists established that normal the struck gene codes synthesis of a geraniltransferaza. Carriers of a horoideremiya are women, males are ill only. Besides degenerate and dystrophic changes of a uvealny path the photoreceptor device is involved in pathological process. Most often changes of sticks in a peripheral part of a retina are found. It is caused by progressing of ischemia.
Damage of a pigmentary epithelium conducts to a congestion of granules of a pigment which at a late stage get into thickness of all internal cover of an eye. Change of very tectonics of an epitelialny layer turns out to be consequence of it. Total loss of sight develops only at defeat of two and more layers of a retina. According to other pathogenetic theory, emergence of a horoideremiya is connected with violation of an expression of protein REP1. Normal the person has a protein of REP2 which on structure for 75% corresponds to REP1. Structural similarity allows to compensate visual dysfunction. However at total violation of an expression of proteins of this group development of a horoideremiya is inevitable.
The first symptoms of a disease arise at boys at early age. Patients show complaints to violations of sight in night-time. There is a discomfort in eyes which is shown feeling of "sand" under centuries. Performance of visual work leads to a headache which irradiates in nadbrovny arches, temporal and frontal lobes. Up to 40 years of function of the central sight are not changed. At patients after achievement of 50-60-year age besides the progressing visual dysfunction functions of color perception are broken. Tunnel sight long time remains safe.
Character of a course of a disease can significantly differ among certain family members. Every year expressiveness of symptomatology increases that quite often leads to a blindness. At easy degree visual dysfunction is minimum. At a heavy current the progressing decrease in visual acuity leads to sight loss by 40-45 years. Clinical manifestations at women manage to be revealed only at application of tool methods of diagnostics. In rare instances female patients note deterioration in visual functions in twilight that demands differentiation with the acquired gemeralopiya.
In 10-30 years from the moment of emergence of the first signs of a horoideremiya the gemeralopiya develops. The risk of accession of pathogenic microflora with the subsequent emergence of a bacterial or virus horioretinit increases. The congestion of pigmentotsit in the field of trabekulyarny network leads to violation of outflow of intraocular liquid and increase in intraocular pressure. The high probability of development of an oftalmogipertenziya is observed, is more rare – secondary glaucoma. Amavroz arises at a degeneration of several layers of an internal cover of an eyeball.
Diagnosis is based on data of the anamnesis and the genetic analysis, results of specific methods of inspection. Point such anamnestichesky data as presence of pathology at men on the maternal line to development of a disease in the child. Tool diagnostics includes:
- To Oftalmoskopy. At survey of an eye bottom congestions of pigmentary granules which have an appearance of "a metal reflex" come to light. Deposits of a pigment are visualized in all quadrants of a retina. Signs of an atrophy of capillaries of a horioidea up to emergence of false impression of total absence of a vascular cover are visible. The Makulyarny and peripapillyarny zone are not changed.
- To Elektroretinografy. Gradual transition from the normal electroretinogram to subnormal is defined. When studying dark adaptation increase in a bacillary threshold is noted. At the last stages of ERG is not registered. The general and local kinds of the procedure are applied.
- To Vizometry. At day lighting visual acuity long time remains. When carrying out a research in the darkened room the expressed visual dysfunction is defined. Visual functions often decrease only in old age.
- Perimetry. Concentric narrowing of visual fields or the discrete, focal and circular centers of defeat is observed. Function of peripheral perception is significantly broken at not changed central at young age. After 50-60 years even islands of the central sight gradually disappear.
- Fluorescent angiography of a retina. At initial stages of change of vessels of large and average diameter are absent. When progressing a disease there are their sclerous changes that leads to emergence of whitish-yellow coloring and the selective centers of coloring. At terminal stages the capillary network is not visualized. Against the background of skler only single large vessels are visible.
Differential diagnostics is carried out with peripheral dystrophy as "cobblestone road", an atrophy Herat, the H-connected pigmentary retinit, a circular degeneration of a vascular cover and a retina. Distinctive feature of a pigmentary retinit – loss not only peripheral, but also central sight. Accumulation of an ornitin in blood acts as the reason of dystrophic violations. Changes of an eye bottom at bearers of a pathological gene are presented by redistribution of pigmentotsit in the form of a retikulyarny pattern.
Treatment of a horoideremiya
Etiotropny treatment of a horoideremiya is not developed. The scientist from the Oxford university Robert McLaren with colleagues works on introduction of gene therapy. The essence of a technique is based on introduction of the copy of protein REP1 for the purpose of prevention of further death of photoreceptors. Symptomatic treatment includes:
- Hypotensive means. Are appointed at increase in the intraocular pressure (VGD) for the purpose of stimulation of outflow of watery moisture and prevention of development of secondary glaucoma.
- Vasoprotectives. Medicines improve metabolic processes, normalize permeability of a vascular wall. Etamsylate has Angioprotektorny effect calcium.
- Reparanta. The complex of polypeptide fractions which have tkanespetsifichesky effect is used and regenerations of a mesh cover promote. A way of introduction of pharmacological means – parabulbarny.
- Fermental medicines. Intramuscular injections of cytochrome C are carried out. Medicine improves tissue respiration and stimulates oxidizing processes.
- Vitamin therapy. Oral administration of vitamins C of group B, C, PP and A is shown. Taurine which stimulates regenerator processes and decrease in VGD is in addition used.
Forecast and prevention
The outcome of a disease depends on expressiveness of clinical symptomatology and speed of progressing of violations. Visual acuity long time does not change, however by 50 years displays of visual dysfunction which are followed by violation of perception of color accrue. Specific preventive measures are not developed. The important part is assigned to genetic screening of pathology and use of auxiliary reproductive technologies when planning pregnancy at persons with the burdened family anamnesis. Patients with a horoideremiya have to be on the dispensary account at the ophthalmologist.