Short-sightedness (miopiya) - the anomaly of the refracting force of an eye (refraction) which is characterized by focusing of the image of objects not on an eye retina, and before it. At short-sightedness of people badly distinguishes the remote objects, but well sees close; the visual exhaustion, a headache, violation of twilight sight, the progressing deterioration in visual acuity is noted. Diagnosis of short-sightedness includes a vizometriya, a skiaskopiya, refractometry, an oftalmoskopiya, biomicroscopy, ultrasonography of an eye. At short-sightedness respect for hygiene of sight, glasses wearing with the disseminating lenses, contact lenses is required; carrying out surgical correction of a miopiya by surgical methods (a lensektomiya, implantation of fakichny lenses, a radial keratotomy, a keratoplasty, a kollagenoplastika) or by means of laser surgery (LASIK, SUPER LASIK, LASEK, FRK, etc.).
Short-sightedness in the general population meets quite often: according to WHO data, a miopiya suffers from 25 — 30% of the population of the planet. Most often short-sightedness develops at children's or pubertatny age (from 7 to 15 years) and further or remains at the available level, or progresses. At short-sightedness the light beams proceeding from the objects located in the distance gather in focus not on a retina, as in a normal eye, and ahead of it owing to what the image turns out indistinct, indistinct, greased.
The condition of short-sightedness for the first time was described still by Aristotle in the 4th century BC. In the works the philosopher noted that some people for the best distinction of remote objects are forced to blink eyes and called this phenomenon "" (from Greek - "to squint"). In modern ophthalmology short-sightedness has other name – a miopiya.
Normal, at 100% sight, parallel beams from the objects which are in the distance, having passed through optical environments of an eye, are focused in an image point on a retina. In a miopichny eye the image is formed before a retina, and the svetovosprinimayushchy cover is reached by only the unsharp and indistinct picture. At short-sightedness such situation arises only at perception by an eye of parallel light beams, i.e. at distant sight. The beams proceeding from close objects have the dispersing direction and after refraction in the optical environment of an eye are projected strictly on a retina, forming the accurate and clear image. Therefore the patient with short-sightedness badly sees afar and well close.
For clear distinction of the remote objects it is necessary to give to parallel beams the dispersing direction that is reached by means of special (-point or contact) the disseminating lenses. The refracting lens force specifying on it is how necessary to weaken a refraction of a miopichny eye, it is accepted to express in dioptries () – from this point of view and the size of short-sightedness which is designated by negative value is defined.
Discrepancy to length of its axis refracting forces of optical system of an eye is the cornerstone of short-sightedness. Therefore the short-sightedness mechanism, first, can be connected with the excessive length of an optical axis of an eyeball with the normal refracting force of a cornea and crystalline lens. At short-sightedness length of an eye reaches 30 and more than a mm (with a normal length of an eye at the adult -
In most cases short-sightedness is hereditary. In the presence of a miopiya at both parents short-sightedness at children develops in 50% of cases; at normal sight of parents – only at 8% of children. Non-compliance with requirements of hygiene of sight acts as the frequent reason promoting development of short-sightedness: visual loadings, excessive on duration, at a short distance, insufficient illumination of a workplace, long work at the computer or viewing of the TV, reading in transport, the wrong landing during the reading and the letter.
Quite often development of true short-sightedness is preceded by the false short-sightedness caused by an overload of a tsiliarny (akkomodatsionny) muscle and a spasm of accommodation. Other oftalmopatologiya - an astigmatism, squint, an ambliopiya, , can accompany short-sightedness. Adverse impact on visual function is exerted by the postponed infections, hormonal fluctuations, intoxications, patrimonial injuries, ChMT worsening microcirculation in eye covers. Progressing of short-sightedness is promoted by deficiency of such minerals as Mn, Zn, Cr, Cu, etc., the wrong correction of already revealed miopiya.
Classification of short-sightedness
First of all, distinguish congenital (connected with pre-natal violations of development of an eyeball) and acquired (developed under the influence of adverse factors) short-sightedness. On the leading mechanism of development of short-sightedness allocate axial (at increase in the size of an eyeball) and a refraction miopiya (with the excessive force of the refracting device).
The state which is followed by progressing of short-sightedness on 1 and more in a year is regarded as the progressing miopiya. At constant, significant increase in degree of a miopiya speak about malignant short-sightedness or a miopichesky disease which results in disability on sight. Stationary short-sightedness does not progress and korrigirutsya well by means of lenses (-point or contact).
The so-called, tranzitorny (temporary) short-sightedness proceeding 1-2 weeks develops at hypostasis of a crystalline lens and increase in its refracting force. This state meets at pregnancy, diabetes, reception of corticosteroids, sulfanylamides, in an initial stage of development of a cataract.
According to refractometry and force of necessary correction in dioptries distinguish short-sightedness of weak, average and high degree:
- weak - to-3 inclusive
- average – from-3 to-6 inclusive
- high – more than-6
Degree of high short-sightedness can reach considerable sizes (to-15 and-30 ).
The long time short-sightedness proceeds asymptomatically and often comes to light ophthalmologists during professional surveys. Usually short-sightedness develops or progresses in school days when in the course of study children have to face intensive visual loadings. It is necessary to pay attention that children begin to distinguish worse remote objects, it is bad to see lines on a board, try to approach closer the considered object, looking afar, blink eyes. Except distant sight at short-sightedness also twilight sight worsens: people with a miopiya are guided in night-time worse.
Constant forcing leads tension of eyes to visual exhaustion - the muscular asthenopia which is followed by severe headaches, an ache in eyes, eye-socket pains. Against the background of short-sightedness the geteroforiya, monocular sight and the dispersing sodruzhestvenny squint can develop.
At the progressing short-sightedness patients are forced to change often points and lenses for stronger as after a while they cease to correspond to degree of a miopiya and to correct sight. Progressing of short-sightedness happens in connection with stretching of an eyeball and often meets at teenage age. Lengthening of a front-back axis of an eye at short-sightedness is followed by expansion of an eye crack that gives to small a pucheglaziya. Sklera at stretching and thinning gets a bluish shade because of the translucent vessels. Destruction of a vitreous body can be shown by "a letaniye of front sights", feeling of "wool hanks", "threads" before eyes.
At stretching of an eyeball lengthening of eye vessels, violation of blood supply of a retina, decrease in visual acuity is noted. Fragility of blood vessels can lead to hemorrhages in a mesh cover and a vitreous body. The otsloyka of a retina and the blindness accompanying it can become the most terrible complication of short-sightedness.
Diagnosis of short-sightedness
Diagnosis of short-sightedness demands carrying out ophthalmologic tests, survey of structures of an eye, a research of a refraction, performing ultrasonography of an eye. Vizometriya (visual acuity check) is carried out according to the table with use of set of trial eyeglass lenses and has subjective character. Therefore this type of a research at short-sightedness needs to be supplemented with objective diagnostics: and allow to determine by a skiaskopiya, refractometry which are carried out after a tsikloplegiya the true size of a refraction of an eye.
Carrying out an oftalmoskopiya and biomicroscopy of an eye with Goldman's lens at short-sightedness is necessary for identification of changes on a retina (hemorrhages, dystrophy, a miopichesky cone, Fuchs's spot), protrusions skler (stafiloma), a cataract and so forth. For measurement of a front-back axis of an eye and size of a crystalline lens, assessment of homogeneity of a vitreous body, an exception of an otsloyka of a retina performing ultrasonography of an eye is shown. Differential diagnostics is carried out between true short-sightedness and a false, and also tranzitorny miopiya.
Treatment of short-sightedness
Correction and treatment of short-sightedness can be carried out conservative (medicamentous therapy,-point or contact correction), surgical or laser methods. The medicamentous courses conducted 1-2 times a year allow to prevent progressing of short-sightedness. Respect for hygiene of sight, restriction of physical activities, reception of vitamins of group B and C, use of midriatik for removal of a spasm of accommodation (fenilefrin), performing fabric therapy (an aloe, a vitreous body intramuscularly), reception of nootropic means (piracetam, gopantenovy acid), physiotherapeutic treatment is recommended (laser therapy, magnetotherapy, massage cervical zones, reflexotherapy).
In the course of treatment of short-sightedness ortoptichesky techniques are used: a training of a ciliary muscle with use of negative lenses, hardware treatment (an accommodation training, a lazerstimulyation, tsvetoimpulsny therapy, etc.).
Selection of contact lenses or points with the disseminating (negative) lenses is made for correction of short-sightedness. For preservation of a reserve of accommodation at short-sightedness incomplete correction is, as a rule, carried out. At short-sightedness higher than-3 use of two pairs of glasses or points with bifocal lenses is shown. At a miopiya of high degree glasses are chosen taking into account their shipping. For correction of short-sightedness of weak average degree ortokeratologichesky (night) lenses can be used.
Today in ophthalmology more than twenty methods of refraction and laser surgery are developed for treatment of short-sightedness. Eksimer-lazernaya correction of short-sightedness assumes correction of sight due to change of a form of a cornea, giving of the normal refracting force by it. Laser correction of short-sightedness is carried out at a miopiya to-12-15 and carried out in out-patient conditions. Among methods of laser surgery at a miopiya the greatest distribution was gained by LASIK, SUPER LASIK, EPILASIK, FemtoLASIK, LASEK, photorefractive keratectomy (FRK). These methods differ in extent of influence and way of formation of a surface of a cornea, however, are in essence identical. Complications of treatment of short-sightedness the laser can become hypo - or hyper correction, development of a corneal astigmatism, keratit, conjunctivitis, a syndrome of a dry eye.
Resort to refraction replacement of a crystalline lens (lensektomiya) at short-sightedness of high degree (to –20 ) and loss natural accommodation of an eye. The method consists a crystalline lens and the room in an eye of the intraocular lens (an artificial crystalline lens) having necessary optical power at a distance. Implantation of fakichny lenses as a method of treatment of short-sightedness, is applied at safe natural accommodation. At the same time the crystalline lens is not deleted, but in addition, implant a special lens into the forward or back camera of an eye. By implantation of fakichny lenses correction very high (to –25 ) short-sightedness degrees is carried out.
The method of a radial keratotomy in view of a large number of restrictions in modern surgery of short-sightedness is used seldom. This way assumes drawing on the periphery of a cornea of not through radial cuts which growing together, change a form and optical power of a cornea.
Scleroplastic surgeries at short-sightedness are performed for the purpose of a stop of growth of an eye. In the course of scleroplasticity for a fibrous cover of an eyeball the strips of biological transplants covering an eye and interfering its stretching are got. Other operation – a kollagenoskleroplastika also is directed to control of growth of an eye.
In some cases at short-sightedness carrying out a keratoplasty – change of a donor cornea which by means of program modeling is given a certain form is expedient. Only the highly skilled surgeon-ophthalmologist (the laser surgeon) taking into account specific features of violation of sight can define an optimum method of treatment of short-sightedness.
Forecast and prevention of short-sightedness
At the corresponding correction of stationary short-sightedness in most cases it is possible to keep high visual acuity. At the progressing or malignant short-sightedness the forecast is defined by existence of complications (an ambliopiya, stafily skler, hemorrhages in a retina or a vitreous body, dystrophies or otsloyka of a retina). At high degree of short-sightedness and changes of an eye bottom hard physical work, heavy lifting, the work connected with long visual tension is contraindicated.
Prevention of short-sightedness, especially at children and teenagers, demands development of skills of hygiene of sight, carrying out special gymnastics for eyes and the all-strengthening actions. The large role is played by the routine inspections directed to detection of short-sightedness at risk groups, medical examination of persons with a miopiya, holding preventive actions, rational and timely correction.