Aniridiya is rare, in the majority a case genetically determined disease of eyes of which total or partial absence of an iris of the eye is characteristic. It is clinically shown by decrease in visual acuity, a horizontal nistagm and a photophobia. For diagnosis of a disease it is necessary to perform inspection of forward department of an eyeball, an oftalmoskopiya, a tonometriya, a gonioskopiya, ultrasonic biomicroscopy, to investigate a clinical refraction. It is possible to establish an aniridiya etiology by means of genetic testing. Specific treatment of an aniridiya is based on transplantation of an artificial iris.
Aniridiya (irideremiya) treats a number of the orphan (rare) diseases which are characterized by a hypoplasia of an iris of the eye of eyes. Frequency of spread of a disease averages 1:70000. Carry Gillespie's syndrome and a WAGR syndrome to the diseases associated with an aniridiya. Patients with an irideremiya enter into risk group of development of a cataract, glaucoma, turbidity of a cornea. Due to the existence of a genetic mutation of a gene of PAX6 the probability of developing of pathologies of other bodies and systems of an organism is high.
Hereditary predisposition is observed at 65% of patients with an aniridiya as the disease can be transmitted, both on autosomno-prepotent, and on autosomno-recessive type. In 35% of cases pathology has the sporadic character caused for the first time by the shown mutation. The disease is equally widespread among men's and female, has no racial differences and features in geographical distribution.
Etiologichesky factor of development of a congenital aniridiya is PAX6 gene mutation that is localized on the 11th chromosome. This gene codes transcription factors which at a stage of an embryogenesis induce development of an eyeball, and also regulate processes of differentiation of bodies of the central nervous system, nose, pancreas. In case of pathology of an expression of a gene of PAX6 formation of anatomical structures of an eyeball which happens on 12-14 week of a gestation is broken. The traumatic injury of eyes which is followed by an iris separation at a root can act as the reason of development of an aniridiya.
The pathogenesis of this disease directly depends on degree of functional activity of alleles of a gene of PAX6. Throughout differentiation of an iris degree of an expression of proteinaceous structures of cytokeratins and factors of adhesion decreases. In turn, ability of cages to migration from a nervous crest to the place of formation of a stroma of an iris of the eye is lost.
At low degree of an expression of a gene there is no differentiation of a crystalline lens and pigmentary epithelium of a retina up to standard that is a prerequisite to a combination of a congenital cataract and an aniridiya. When involving in pathological process of a corner of the forward camera of an eye and the trabekulyarny device congenital glaucoma develops. At more mature age glaucoma arises because of formation of sinekhiya. Also as the factor playing a role in development of an aniridiya deficiency of limbalny stem cells acts.
By origin in ophthalmology allocate the congenital and acquired (traumatic) aniridiya forms. Symptoms of a traumatic irideremiya depend on a damage rate of an iris of the eye. From the clinical point of view allocate full, partial and combined with Gillespie and a WARG syndrome an aniridiya.
The full form of a disease is characterized by existence of the small remains of a root of an iris. Clinically the disease is shown by decrease in visual acuity that is connected with an underdevelopment of structures of an eyeball. Extent of decrease in visual acuity directly depends on existence in the anamnesis of a cataract, glaucoma and a keratopatiya. Lack of an iris of the eye leads to the raised photosensitivity. One of symptoms of a full aniridiya is horizontal in combination with squint.
For a partial aniridiya the same symptomatology, as for a full form of pathology is peculiar. But because easy degree of a hypoplasia of a stroma of an iris of the eye is characteristic of a disease, clinical manifestations are poorly expressed.
The WARG syndrome, besides an aniridiya, includes Vilms's tumor (a malignant nefroblastoma), diseases of urinogenital system and a delay of mental development. Often this simptomokompleks includes pancreatitis and a chronic renal failure. Appearance of patients can be followed by a gemigipertrofiya (a hypertrophy of the muscular device of one of half of a body). At early stages of development the syndrome can not have the expressed clinical manifestations that is the reason of hypodiagnostics.
Gillespie's syndrome is characterized by an aniridiya combination to a clinical picture of a cerebellar ataxy and intellectual backwardness. At a number of patients note , decrease in hearing and a stenosis of the valve of a pulmonary artery.
Diagnostics of an aniridiya
At an aniridiya include visual survey of forward departments of eyes, an oftalmoskopiya, a tonometriya, a gonioskopiya, a research of a clinical refraction and ultrasonic biomicroscopy in a complex of diagnostic actions. The genetic analysis allows to define the reason of development of an aniridiya. It will be out only in case of congenital forms of a disease.
At survey of forward departments of eyes it is not possible to visualize an iris of the eye. In special cases small congestions of an iris are observed that is most characteristic of a traumatic or partial aniridiya. The method of an oftalmoskopiya possible to reveal a hypoplasia of the central part of a retina and optic nerve that is peculiar for a full form of an aniridiya.
Tonometriya allows to measure the intraocular pressure (VGD). Increase in VGD is higher than tolerant values is risk factor of glaucoma. With an aniridiya it is recommended to patients to measure VDG by means of the ICare device that allows to carry out manipulation without anesthetics. For the purpose of prevention of development of glaucoma it is necessary to carry out a tonometriya and an oftalmoskopiya in dynamics. Gonioskopiya is required to patients with the raised VDG for additional survey of the forward camera of an eye.
The research of a clinical refraction at patients with an aniridiya is conducted by method of a skiaskopiya, a direct oftalmoskopiya or refractometry. Depending on the accompanying pathology the emmetropichesky, gipermetropichesky and miopichesky refraction can come to light. The method of ultrasonic biomicroscopy allows to estimate residual fabric of an iris of the eye and to investigate an eye bottom at patients with a cataract or a keratopatiya.
Genetic analyses for confirmation of a hereditary aniridiya include carrying out the FISH test and a research on definitions like defect of a gene of PAX6. Carrying out the FISH test is necessary for a WARG syndrome exception. Until carrying out the genetic analysis it is necessary to carry out 1 time in 3 months ultrasonography of kidneys and bodies of a small pelvis. As additional methods of a research the optical coherent tomography, the visual caused potentials and topography of a cornea is applied.
Treatment of an aniridiya
Specific treatment of an aniridiya is based on implantation of an artificial iris. The artificial limb consists of special hydrogel with the opening corresponding to a pupil. Color of an artificial iris is selected according to color of eyes of the patient. Surgery is carried out by means of transskleralny surgical access.
Implantation of an artificial iris is shown to patients with a traumatic aniridiya. At congenital forms of a disease surgery is carried out only if the risk of damage of a cornea is minimum. At an aniridiya combination to a cataract tactics of operation comes down to implantation of the artificial limb replacing both an iris, and a crystalline lens.
Symptomatic treatment includes use of cosmetic contact lenses for concealment of defect of an iris of the eye. At increase in intraocular pressure it is recommended to use drops from group of inhibitors of a karboangidraza, prostaglandins and beta-blockers. For prevention of development of a keratopatiya it is necessary to use the moistening drops and gels. All patients need to wear sunglasses which provide to 100% blocking of ultraviolet rays.
Forecast and prevention of an aniridiya
Specific measures for prevention of an aniridiya are not developed since the disease is connected with a genetic mutation. The family in which one of parents is sick with an aniridiya before planning of pregnancy needs to consult at the geneticist and the ophthalmologist. Prevention of a traumatic aniridiya comes down to observance of the equipment of personal security since the strong blow can become the reason of a separation of an iris of the eye.
At observance of all recommendations the forecast at a congenital aniridiya for life favorable. Development of glaucoma or association of an aniridiya with Gillespie and a WARG syndrome can become the reason of an early invalidization of the patient.