Koloboma is a polietiologichesky disease of which the isolated or combined splitting of an iris, retina, a vascular cover, an optic nerve or century is characteristic. The general clinical manifestations of all forms of a koloboma are decrease in visual acuity, feeling of pain in eyes, astenopichesky complaints. Specific diagnostics depends on type of defeat and can include external examination, a vizometriya, an oftalmoskopiya, biomicroscopy, ultrasonography in the V-mode, KT, MPT. Conservative methods of treatment of a koloboma it is not developed. Surgical tactics depends on a form of a disease and can include a peritomiya, a kollagenoplastika, a lazerokoagulyation, a vitrektomiya.
Koloboma is acquired or congenital pathology of an organ of vision which is shown by full or partial splitting of its structures. The term of a kolobom was entered by Walter in 1821, in translation from Greek "the absent part" means. Koloboma frequency in population makes about 0,5-0,7 on 10000 newborns. According to statistical data, among all forms the koloboma of an iris is most of all widespread (1:6000). Pathology with an identical frequency occurs among persons men's and female. Congenital splitting of a vascular cover is one of the reasons of a blindness and violation of sight at children's age. The disease most often meets in China (7,5:10000), the USA (2,6:10000) and France (1,4:10000).
The congenital koloboma is genetically determined disease with mainly autosomno-prepotent type of inheritance. Variable mutations of a gene of RAH6 are associated with a large number of malformations of eyes including kolobomy. In too time it is proved that anomalies of methylation of DNA of separate histones under the influence of factors of the external environment lead to epigenetic changes which can also be the trigger of this pathology. Splitting of structures of an eyeball is a consequence of violation of closing of a germinal crack on 4-5 week of an embryonal development. Infection of mother with a cytomegalovirus on early terms of a gestation can be the cause of congenital defeat.
Unlike other forms, the koloboma of an iris of the eye can be inherited both on autosomno-prepotent, and on autosomno-recessive type. Autosomno-dominantny the type is associated with defeat of a gene of RAH6 with localization in a short shoulder of the 11th chromosome. The type of the mutated gene at an autosomno-recessive way of transfer is not established. At emergence of a deletion 24-DEL, NT1353 splitting of an iris is, as a rule, combined with a mikroftalmiya. Development of the acquired form is influenced by such factors as abuse of alcoholic drinks and a hormonal imbalance. The Iridoretinalny koloboma is formed at a mutation of a gene of SHH of a long shoulder of the 7th chromosome, horioretinalny – at defeat of a gene of GDF6 8q22 or RAH6 11p13. The reason of the combined splitting of a disk of an optic nerve, retinas and horioide SHH gene mutation with localization on a chromosome 7q36 is.
Koloboma a century of the acquired genesis often arises owing to a necrosis of fabrics or formation of hems at traumatic damages. Postoperative defects against the background of an iridektomiya at pathological new growths of an iris can provoke this pathology also.
From the clinical point of view in ophthalmology allocate koloby irises, retinas, a vascular cover, a disk of an optic nerve, a crystalline lens and a century. When involving in pathological process of all above-stated structures the full koloboma develops, at less extensive defeat – partial. Splitting can be unilateral or affect both eyes. At a typical form defect is localized in a nizhnenazalny quadrant that is caused by topography of a crack of the eye channel. Atipicheska name koloby with localization in other departments of an organ of vision. Clinical manifestations depend on a disease form.
At a koloboma of an iris the expressed cosmetic defect reminding a pear or a keyhole is formed. Against the background of normal or insignificant decrease in visual acuity patients are incapable to regulate the volume of receipt of rays of light to a retina. Pathology a svetovospriyatiya is result. At defeat of all thickness of a vascular cover the scotoma symptomatology joins (emergence of sites of blackout before eyes). The bilateral koloboma leads to development of a nistagm. The disease can proceed separately or to be one of manifestations of Chardzh or Ekardi of syndromes.
Extent of decrease in visual acuity at a koloboma of an optic nerve depends on defeat volume. At the isolated defect sight can meet standard, in case of a combination with mikroftalmy or splitting of other structures of an eyeball the total blindness is possible. Most of patients note at themselves doubling before eyes, dizziness, violation of binocular sight in the form of a strabizm. The disease often is followed by development of a clinical picture of an astigmatism in miopichesky type (decrease in visual acuity, distortion of the image before eyes). The congenital form of pathology is often combined with Goldenkhar's syndromes, Down and Edwards, and also an epidermalny nevus.
The latent current is characteristic of the isolated koloboma of a retina. Patients show complaints only at development of secondary complications in the form of the gaps which are followed by peeling of a retina. Long existence of pathology leads to formation of scotomas. Anomaly is clinically shown by sites of blackout before eyes. When splitting a crystalline lens its refracting function is broken that becomes the reason of formation of zones with a different svetoprelomleniye. Clinically the disease is shown by astigmatism symptomatology. Koloboma, as a rule, is followed a century by an incomplete smykaniye, traumatizing a conjunctiva eyelashes, development of erosive defects. This pathology often is complicated by secondary conjunctivitis.
Diagnostics of a koloboma
Methods of diagnostics of a koloboma depend on a disease form. Koloboma of an iris of the eye is characterized by emergence of defect in the form of a pear or a keyhole which are visualized at external examination. When carrying out ultrasonic biomicroscopy the congenital form in most cases is followed by a hypoplasia of a tsiliarny body. Tsiliarny shoots have the smaller length and big width in comparison with norm. The randomness of fibers and an illegibility of structure of a tsinnovy sheaf indicates its underdevelopment. Extent of decrease in visual acuity is defined by a viziometriya method.
At a koloboma of an optic nerve insignificant increase in its diameter is defined by method of an oftalmoskopiya. Roundish light deepenings with accurately limited edges are visualized. A method of ultrasonic scanning in the V-mode or the computer tomography (CT) allow to find deep defects on a back pole of an eyeball. In some cases at the magnetic and resonant tomography (MRT) the hypoplasia of intra cranial department of an optic nerve is defined. Aged after 20 years the regmatogenny otsloyka of a retina is often formed. When progressing at patients MRT symptoms of makulyarny hypostasis decide that often leads to a gap and an otsloyka of a retina on pathological deepenings in a disk of an optic nerve. The histologic research allows to reveal concentric the focused fibers of smooth muscles.
Koloboma of a vascular cover at an oftalmoskopiya represents formation of white color with scalloped edges. As a rule, defect is localized in the lower departments of an eye bottom. At a vizometriya the miopiya which degree depends on defeat volume is defined. At biomicroscopy of a kolobom of a crystalline lens has an appearance of splitting which is located in a nizhnevnutrenny quadrant. Progressing of pathology leads to the expressed deformation of the equator of a crystalline lens.
Treatment of a koloboma
Tactics of treatment of a koloboma depends on a form and extensiveness of defeat. At insignificant splitting of an iris and lack of dysfunction of an organ of vision surgery is not shown. At decrease in visual acuity it is necessary to execute a peritomiya with the subsequent sewing together of edges of an iris of the eye. For the purpose of the prevention of further progressing of a koloboma the behavior of a kollagenoplastika is recommended. The purpose of surgery is formation of a collagenic framework which interferes with progressing of a koloboma.
At damage of an optic nerve the lazerokoagulyation is shown only to patients with formation of a subretinalny neovascular membrane. Vitrektomiya with the subsequent laser coagulation of a retina is recommended at decrease in visual acuity to 0,3 dioptries from the accompanying makulyarny otsloyky retina. In addition, method of treatment of a horioretinalny koloboma is endodrainage through an intermediate membrane with further laser photocoagulation of a mesh cover around a regional area. At the expressed koloboma of a crystalline lens its removal with the subsequent implantation of an intraocular lens is necessary. In turn, defect in the form of splitting of a century is eliminated by means of a blefaroplastika.
Forecast and prevention
Specific preventive measures for the prevention of development of a koloboma it is not developed. For prevention of violations a svetovospriyatiya at a koloboma of an iris use of mesh points or the darkened contact lenses with the transparent center is recommended. To patients with primary displays of this pathology it is necessary to have two times a year examination at the ophthalmologist with obligatory carrying out a vizometriya, biomicroscopy and an oftalmoskopiya of an eye bottom. At insignificant splitting of structures of an eyeball the forecast for life and working capacity favorable. Extensive defeat can be complicated by total decrease in visual acuity up to a total blindness that leads to the patient's invalidization.