Cataract – pathology of svetoprelomlyayushchy structure of an eye – a crystalline lens, characterized by its turbidity and loss of natural transparency. The cataract is shown by sight "zatumanennost", deterioration in night vision, weakening of color perception, sensitivity to bright light, a diplopiya. Ophthalmologic inspection at a cataract includes a vizometriya, perimetry, an oftalmoskopiya, biomicroscopy, a tonometriya, refractometry, ophthalmometry, ultrasonography scanning of an eye, electrophysiological researches. For delay of progressing of a cataract conservative therapy is carried out; removal of a cataract is made by microsurgical intervention with replacement of a crystalline lens by an intraocular lens.
Cataract (from Greek katarrhaktes - falls) - the turbidity or change of color of a part or all crystalline lens leading to reduction of its svetoprovodimost and decrease in visual acuity. According to WHO, a half of cases of a blindness is around the world caused by a cataract. In age group of 50-60 years the cataract comes to light at 15% of the population, 70-80 years - at 26%-46%, 80 years – practically at everyone are more senior. Among congenital diseases of eyes the cataract also takes the leading positions. Big prevalence and social consequences of a disease do a cataract of one of the most urgent problems of modern ophthalmology.
The crystalline lens is a part dioptric (photoconductive and svetoprelomlyayushchy) the device of an eye, the located kzada from an iris of the eye, opposite to a pupil. Structurally the crystalline lens is formed by the capsule (bag), a kapsulyarny epithelium and lenticular substance. Crystalline lens surfaces (forward and back) have spherical shape with a different radius of curvature. Diameter of a crystalline lens makes 9-10 mm. A crystalline lens - bessosudisty epitelialny education; nutrients come to it by diffusion from surrounding intraocular liquid.
On the optical properties the crystalline lens represents a biological biconvex transparent lens which function consists in refraction of the beams entering it and their focusing on an eye retina. The refracting force of a crystalline lens is non-uniform on thickness and depends on a condition of accommodation (at rest - 19,11 ; in a condition of tension - 33,06 ).
Any change of a form, size, the provision of a crystalline lens leads to considerable violations of its functions. Among anomalies and pathology of a crystalline lens the afakiya (lack of a crystalline lens), a mikrofakiya (reduction of the sizes), a koloboma (lack of a part of a lens and its deformation), (protrusion of a surface in the form of a cone), a cataract occurs. Formation of a cataract can happen in any of crystalline lens layers.
The etiology and mechanisms of a kataraktogenez - development of a cataract speak from positions of several theories, however any of them does not give irrefragable answer on a question of causes of illness.
In ophthalmology the greatest distribution was gained by the theory of free radical oxidation which explains the mechanism of formation of a cataract from the point of view of education in an organism of free radicals - the unstable organic molecules with an unpaired electron which are easily entering chemical reactions and causing the most severe oxidizing stress. It is considered that perekisny oxidation of lipids - interaction of free radicals with lipids, especially nonsaturated fatty acids, leads to destruction of membranes of cages, as causes development of a senile and diabetic cataract, glaucoma, cirrhosis, hepatitis, violations of microcirculation in brain tissues. Education of free radicals in an organism, first of all, is promoted by smoking and ultra-violet radiation.
An important role in the mechanism of development of a cataract is played by age decrease in antioxidant protection and deficiency of natural antioxidants (vitamins A, E, glutathione, etc.). Besides, physical and chemical properties of proteinaceous fibers of a crystalline lens which make over 50% in its structure change with age. Violation of metabolism of a crystalline lens and development of pomutneniye can be connected with change of composition of intraocular liquid at recurrent inflammatory diseases of an eye (to an iridotsiklita, you horioretinit), and also dysfunction of a tsiliarny body and an iris (Fuchs's syndrome), terminal glaucoma, a pigmentary degeneration and an otsloyka of a retina.
Besides age involution, starvation, anemia, excessive insolation, influence of radiation, toxic poisonings (mercury, thallium, naphthalene, an ergot) contribute to development of a cataract deep general exhaustion after serious infectious diseases (typhus, malaria, smallpox, etc.). As risk factors of development of a cataract serve endokrinopatiya (diabetes, a tetaniye, muscular dystrophy, an adipozogenitalny syndrome), a Down syndrome, skin diseases (a sklerodermiya, eczema, neurodermatitis, Jacobi's poykilodermiya). The complicated cataracts can arise at mechanical and kontuzionny injuries of an eye, burns of eyes, the undergone eye operations, unsuccessful heredity on a cataract in a family, short-sightedness of high degree, uveita.
The congenital cataract is in most cases caused by toxic impacts on an embryo in the period of laying of a crystalline lens. Distinguish the infections (flu, a rubella, herpes, measles, toxoplasmosis) transferred the pregnant woman from the reasons of a congenital cataract, , reception of corticosteroids, etc. The congenital cataract can meet at hereditary syndromes and be combined with malformations of other bodies.
Classification of a cataract
In ophthalmology of a cataract are divided into two big groups: congenital and acquired. Congenital cataracts are, as a rule, limited on the area and statsionarna (do not progress); at the acquired cataracts of change in a crystalline lens progress.
Depending on an etiology, distinguish from the acquired cataracts senile (senile, age - about 70%), complicated (at diseases of eyes – about 20%), traumatic (at eye wounds), beam (at damage of a crystalline lens by x-ray, radiation, infrared radiation), toxic (at chemical and medicinal intoxications), the cataracts connected with the general diseases.
On localization of turbidity in a crystalline lens distinguish:
- forward polar cataract – settles down under the capsule in the field of a forward pole of a crystalline lens; turbidity has an appearance of a round spot of whitish and grayish color;
- back polar cataract - settles down under the capsule of a back pole of a crystalline lens; on color and a form it is similar to a forward polar cataract;
- spindle-shaped cataract – settles down on a perednezadny axis of a crystalline lens; has the spindle form, by the form reminds a thin gray tape;
- nuclear cataract – settles down in the center of a crystalline lens;
- layered (zonular) cataract – settles down around a crystalline lens kernel, at the same time muddy and transparent layers alternate;
- cortical (kortikalny) cataract – settles down on the outer edge of a cover of a crystalline lens; has an appearance of whitish wedge-shaped inclusions;
- back subkapsulyarny - settles down under the capsule behind a crystalline lens;
- full (total) cataract – always bilateral, it is characterized by turbidity of all substance and the capsule of a crystalline lens.
All called morphological forms occur among a congenital cataract; among acquired - nuclear, cortical and full.
The cataract passes 4 stages in this connection distinguish an initial, unripe, mature and overripe cataract in the maturing.
In a stage of initial maturing of a cataract the crystalline lens ovodneniye which is characterized by a congestion between fibers of a cortical layer of excessive liquid with formation, so-called, "water cracks" takes place. Turbidity at an initial cataract are localized in bark, on the periphery, out of an optical zone of a crystalline lens therefore do not affect visual acuity.
The stage of an unripe cataract is characterized by progressing of pomutneniye which mention the central optical area of a crystalline lens. The biomicroscopic research finds a cataract, alternating with transparent sites. At this stage of maturing of a cataract noticeable decrease in visual acuity is noted.
At a stage of a mature cataract consolidation and full turbidity of substance of a crystalline lens is observed. The kernel of a crystalline lens and its back kortikalny layers in the course of biomicroscopy of an eye are not looked through. External examination reveals a pupil of milky-white or gray color. Visual acuity at a mature cataract varies from 0,1-0,2 to svetooshchushcheniye level.
In a stage of an overripe cataract there is a disintegration of lenticular fibers, fluidifying of cortical substance of a crystalline lens, wrinkling of the capsule. Bark becomes a homogeneous milky-white shade. A kernel, having lost a support, falls down. The crystalline lens becomes similar to the sack filled with muddy liquid with the kernel lying at the bottom. Such overripe cataract is called a morganiyevy cataract. To this stage there corresponds the total blindness.
The overripe cataract can be complicated by the fakogenny (fakolitichesky) glaucoma connected with a contamination of natural ways of outflow of VGZh macrophages and proteinaceous molecules. In certain cases there can be a rupture of the capsule of a crystalline lens and an exit in a cavity of an eye of a proteinaceous detrit that involves development of a fakolitichesky iridotsiklit.
Maturing of a cataract can be fast-progressing, slowly progressing and moderately progressing. At the first option from an initial stage to an extensive cataract there pass 4-6 years. The fast-progressing cataract develops approximately in 12% of observations. Slow maturing of a cataract happens within 10-15 years and occurs at 15% of patients. Moderate progressing of a cataract in 70% cases proceeds during 6-10 years.
Expressiveness of clinical manifestations depends on a cataract stage. Visual acuity at an initial cataract can not suffer. Early symptoms of a disease can be doubling of objects (diplopiya), flashing of "front sights" before eyes, a sight illegibility ("as in fog"), coloring of visible objects in a yellowish shade. Patients with a cataract note difficulties by the letter, reading, work with fine details.
Hypersensibility of eyes to light, deterioration in night vision, easing of color perception, need of use of bright lighting when reading, emergence of "aura" is typical for clinic of a cataract at a view of any light sources. Sight at a cataract changes towards short-sightedness therefore patients with the expressed far-sightedness sometimes suddenly find out that they perfectly see close without points. The visible image blurs before eyes, however it is not possible to correct it by means of points or contact lenses in any way, despite change of level of dioptries.
In a stage of unripe and especially mature cataract visual acuity decreases sharply, lost subject sight, only the svetooshchushcheniye remains. In the course of maturing of a cataract color of a pupil becomes milky-white instead of black.
Diagnosis of a cataract
Detection of a cataract is carried out by the ophthalmologist on the basis of a number of standard and additional inspections.
Routine ophthalmologic inspection at suspicion of a cataract includes a vizometriya (visual acuity check), perimetry (definition of fields of vision), color testing, a tonometriya (measurement of intraocular pressure), biomicroscopy (an eyeball research by means of a slot-hole lamp), an oftalmoskopiya (studying of an eye bottom). In total standard ophthalmologic inspection allows to reveal such symptoms of a cataract as decrease in visual acuity, violation of color perception; to investigate structure of a crystalline lens, to estimate localization and size of turbidity, to find dislocation of a crystalline lens etc. At impossibility of survey of an eye bottom, at the expressed cataract, resort to a research of the entopichesky phenomena (mechanophosphene and an autooftalmoskopiya phenomenon) allowing to judge a condition of the neuroreceptor device of a retina.
At a cataract carry refractometry, ophthalmometry, eye OUSE scanning to special methods of inspection in And - and In - the mode, ultrasonic biomicroscopy, etc. Additional methods allow the surgeon-ophthalmologist to calculate force of an intraocular lens (an artificial crystalline lens), to decide on an optimum operational technique.
For assessment of a functional condition of a retina, an optic nerve and the central departments of the visual analyzer at a cataract electrophysiological researches are conducted: elektrookulografiya (EOG), elektroretinografiya (ERG), registration of the visual caused potentials (VCP).
Treatment of a cataract
In initial stages of a senile cataract the conservative therapy including instillations of eye drops is applied (the azapentaprices, , the combined medicines with cytochrome C, taurine, etc.). Similar measures do not lead to a rassasyvaniye of pomutneniye of a crystalline lens but only slow down progressing of a cataract.
The sense of so-called, replacement therapy consists in introduction of substances which lack leads to development of a cataract. Therefore amino acids, vitamins (Riboflavinum, nicotinic acid, ascorbic acid), antioxidants, iodide potassium, ATP, etc. substances are a part of eye drops. Medicine of the azapentaprices has other mechanism of action – due to activation of proteolytic enzymes, it to a certain extent promotes a rassasyvaniye of opaque proteinaceous structures of a crystalline lens.
Conservative treatment of a cataract is ineffective therefore by the only method of elimination pathology and restoration of sight serves microsurgery – removal of the changed crystalline lens and its replacement with an intraocular lens. Possibilities of modern microsurgery of an eye save from need to wait for full maturing of a cataract for its removal.
Medical indications to expeditious treatment include: the bulking-up cataract, an overripe cataract, an incomplete dislocation or dislocation of a crystalline lens, detection of secondary glaucoma, the accompanying pathology of an eye bottom demanding treatment (a diabetic retinopathy, an otsloyka of a retina, etc.). Additional indications to surgical treatment of a cataract are defined by the professional and household needs for sight improvement of quality. At a bilateral cataract operate the eye having lower visual acuity in the beginning.
In modern surgery of a cataract several ways of removal of the dimmed crystalline lens are used: ekstrakapsulyarny and intrakapsulyarny extraction of a cataract, ultrasonic and laser fakoemulsifikation.
The method of ekstrakapsulyarny extraction of a cataract consists kernels of a crystalline lens and lenticular masses at a distance; at the same time the back capsule of a crystalline lens remains in an eye, dividing forward and back pieces of an eye. In the course of intrakapsulyarny extraction of a cataract the crystalline lens is removed together with the capsule. Both operations are quite traumatic since they demand performance of a big section of a cornea and suture.
The modern standard of surgery of a cataract is the ultrasonic fakoemulsifikation with implantation of IOL. At the same time through a section about 3 mm are entered into the forward camera of an eye an ultrasonic tip of the device-fakoemulsifikatora under the influence of which substance of a crystalline lens turns into an emulsion and aspirirutsya from an eye. The similar algorithm is used at a laser fakoemulsifikation of a cataract during which for crushing of a crystalline lens the laser radiator is used.
Numerous options of a fakoemulsifikation of a cataract allow to solve at the same time accompanying problems: to correct a corneal astigmatism (a fakoemulsifikation from soft torichesky IOL), a presbiopiya (a fakoemulsifikation from multifocal IOL), in one stage to carry out surgical treatment of glaucoma (a cataract fakoemulsifikation with IOL + antiglaukomatozny operation), etc.
Forecast and prevention of a cataract
Despite speed of carrying out and relative safety of extraction of a cataract, in 1-1,5% of observations in the post-operational period inflammatory reactions (uveita, iridotsiklita), raising of VGD, IOL shift, hemorrhage can develop in the forward camera of an eye, an otsloyka of a retina, a secondary cataract. At the full shift of IOL the vitrektomiya and sutural fixing of the deployed IOL is made.
The most serious forecast concerning visual function is accompanied by a congenital cataract as in this case changes in the neuroreceptor device of an eye, as a rule, take place. Surgical treatment of the acquired cataract, in most cases leads to achievement of the acceptable visual acuity, and is frequent – and to restoration of working ability of the patient.
Prevention of congenital cataracts demands the prevention of viral diseases during pregnancy, an exception of radiative effects. For prevention of development of the acquired cataract, especially at young age, antioxidant protection of an organism, earlier treatment of the accompanying general and ophthalmologic pathology, the prevention of injuries of eye, annual professional surveys by the ophthalmologist is necessary.