Afakiya is a pathological condition of an organ of vision of which lack of a crystalline lens in an eyeball is characteristic. Clinically the disease is shown by decrease in visual acuity, trembling of an iris of the eye, loss of ability to accommodation and astenopichesky complaints. Diagnostics of an afakiya includes carrying out a vizometriya, gonioskopiya, biomicroscopy, an oftalmoskopiya, refractometry and ultrasound examination of an eye. Conservative therapy consists in correction of an afakiya by means of contact lenses and points. Tactics of surgical treatment comes down to implantation of an artificial crystalline lens (an intraocular lens) in an afakichny eye.
Afakiya, or lack of a crystalline lens is a disease of eyes of the congenital or acquired genesis which is followed by refraction pathology, decrease in visual acuity and inability to accommodation. The congenital afakiya is among orphan diseases, the frequency of its development in population is studied not enough. At the same time, the number of the postoperative afakiya which are a consequence of extraction of a cataract increases every year. The risk of development of the acquired disease form sharply increases in age after 40. Increase in number of the acquired disease forms in economically safe countries is predicted. Development both the congenital, and acquired form of pathology is not influenced racial also by a sex.
Clinical classification of an afakiya includes the congenital and acquired disease forms. In ophthalmology allocate two kinds of a congenital afakiya: primary (it is caused by a crystalline lens aplaziya) and secondary (develops at a pre-natal resorption of a crystalline lens). Depending on prevalence lack of a crystalline lens happens monocular (unilateral) and binocular (bilateral).
A key role in development of a congenital afakiya is played by violation of development of a crystalline lens at an embryogenesis stage. At primary form of congenital defect there is no separation of a lenticular bubble from an external ektoderma. Genes of PAX6 and BMP4 normal are responsible for this process. Depending on extent of decrease in an expression of these genes at certain stages of an embryonal development formation of a forward lentikonus, a perednekapsulny cataract and Peters's anomaly, combined with lack of a crystalline lens is possible. It is experimentally proved that the arrest of development of structures of an eyeball at a stage of corneal and lenticular contact leads to primary form of a congenital afakiya.
The idiopathic absorption of a crystalline lens arising spontaneously is the reason of a secondary form of a disease. One of theories of its development it is considered to be a spontaneous mutation that provokes violation of formation of a basal membrane of which in the course of an embryogenesis the crystalline lens capsule has to be formed.
In an etiology of the acquired afakiya the leading role is assigned to surgical extraction of a cataract, dislocation and an incomplete dislocation of a crystalline lens. Also the getting wounds and contusions of an eyeball can act as the reasons of this disease.
Specific symptom of an afakiya is (trembling of an iris) which develops at the movement of eyes. At inspection at patients decrease in visual acuity and ability to accommodation is noted. In the predictive plan of the most adverse the unilateral form of a disease as the clinical picture is complicated by an anizeykoniya is. The anomaly induced by organic pathology is followed by distinction at a rate of the image on a retina of eyes owing to what binocular sight sharply worsens.
The congenital form of pathology is characterized by the progressing decrease in visual acuity at relative stability of other clinical manifestations. Lack of timely treatment can become the blindness reason. For a postoperative form of an afakiya staging of a course of the main disease which served as the reason of performing surgery on removal of a crystalline lens is peculiar. The clinical picture of a traumatic afakiya is characterized by the progressing increase of symptomatology which early manifestations are an intensive pain syndrome with increase of local hypostasis and progrediyentny decrease in visual acuity.
From astenopichesky complaints at patients with an afakiya emergence of fog before eyes, low ability to fixing and doubling of the image is noted. Nonspecific displays of a disease are the headache, the general weakness, the increased irritability.
The congenital form of an afakiya or removal of a crystalline lens at children's age is complicated by a mikroftalmiya. At total absence of the capsule of a crystalline lens the vitreous body is limited only to a boundary membrane. It serves as the reason of formation of hernia of a vitreous body. In case of a rupture of a boundary membrane contents of a vitreous body leave in the forward camera of an eye. At the same time contact correction is a provocative factor of development of a keratit, formation of hems on a cornea, in a corneal skleralnoy of area and a limb.
Diagnostics of an afakiya
For diagnosis "afakiya" expedient is carrying out such methods of a research as a vizometriya, a gonioskopiya, eye biomicroscopy, an oftalmoskopiya, refractometry and ultrasonography of an eye. By means of a vizometriya it is possible to establish extent of decrease in visual acuity. This method of a research is shown to all patients before carrying out correction. At a gonioskopiya the expressed deepening of the forward camera of an eye is observed. Carrying out an oftalmoskopiya is necessary for detection of the accompanying pathology and the choice of further tactics of treatment. Besides cicatricial changes in area of a retina and a horioidea, at an afakiya the central horioretinalny dystrophy of a retina, a partial atrophy of an optic nerve and the peripheral horioretinalny centers often comes to light.
Refractometry technique at a unilateral form of a disease allows to reveal decrease in a refraction on 9,0 – 12,0 dioptries on an afakichny eye. Gipermetropiya is defined at children after extraction of a congenital cataract and averages 10,0 – 13,0 dioptries. Development of a mikroftalm at a congenital afakiya also promotes far-sightedness. The method of biomicroscopy did not possible to visualize an optical cut of a crystalline lens. In rare instances the capsule remains come to light. At a research of figures of Purkinye-Sansón, there is no reflection from a back and forward surface of a crystalline lens.
Treatment of an afakiya
Correction of an afakiya is carried out by means of points, contact and intraocular lenses. The indication to-point correction of sight is the bilateral form of a disease. At a unilateral afakiya points are recommended only at intolerance of contact methods of correction. The choice of glass for an emmetropichny eye is complicated since even glass in +10 dioptries is not comparable to the refracting crystalline lens force which equals to 19 dioptries. It is caused by the fact that index of refraction of liquid which surrounds a crystalline lens, above, than the air environment surrounding glass.
The optical power of a glass lens depends on the patient's refraction. At a gipermetropiya it is necessary to choose glasses with stronger optics, than at a miopiya. There is no need for purpose of methods of correction of sight to patients with high degree of a miopiya before removal of a crystalline lens. Due to the lack of ability to accommodation follows the patient points for work at a short distance on 3,0 dioptries to appoint stronger, than for distant vision.
Contact or intraocular correction of sight are shown to patients with a monocular afakiya. Purpose of points to patients with this form of a disease will aggravate an anizeykoniya. During surgery (intraocular correction) implantation of an artificial lens with individually picked up optical power is carried out. The most preferable option of treatment is use of zadnekamerny lenses since being localized in the location of a natural lens, they provide high quality of sight. The congenital afakiya by means of this technique can be corrected only after achievement of two-year age by the child.
Forecast and prevention of an afakiya
The forecast for life and working capacity at the correct correction of an afakiya favorable. In the absence of timely treatment high risk of full loss of sight that in the subsequent conducts to an invalidization.
In ophthalmologic practice specific measures for prevention of a congenital afakiya are absent. For prevention of development of the acquired forms of a disease it is necessary to have annual examination at the ophthalmologist. It will help to diagnose in due time those diseases which can lead to expeditious removal of a crystalline lens. The persons which are in risk group on getting injured of an eye in connection with features of a profession need to use goggles or masks in working hours.