SQUINT

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SQUINT (strabismus, heterotropia) — a deviation of a visual axis of one of eyes from a joint point of fixing at disturbance of solid vision. Frequency of distribution To. — 1,5 — 2%.

The reasons To. there can be diseases and damages of c. N of page, inborn distinctions in an anatomo-optical structure of both eyes, ametropias, sharp decrease in sight or a blindness on one eye. Also hereditary predisposition to matters To. As a result of action of the specified reasons various departments and touch and motive bonds are surprised visual analyzer (see) on which normal depends solid vision (see) that leads to its frustration or interferes with its formation. At decrease in sight or a blindness of one eye To. arises due to the lack of an incentive to a fuziya (merge). At insufficient fusional ability of eyes can deviate owing to strengthened (at far-sightedness) or weakened (at short-sightedness) accommodation and the related convergence.

Distinguish paralytic To., caused by damage of nerves (nn. oculomotorius, trochlearis, abducens), innervating outside muscles of an eye, and consensual To., when the mechanism of binocular fixing of an object falls apart and fuziya (see), and oculomotor muscles almost do not suffer.

Paralytic squint

in case of the isolated defeat of one of muscles a sore eye deviates to the opposite side (a corner of primary deviation). The size of a deviation of an eye (squint angle) increases in process of movement of a look towards action of the affected muscle. During the fixing of a subject a healthy eye (a corner of a secondary deviation), and on much bigger corner deviates by the paralyzed eye, than on what a sore eye was rejected (a corner of a secondary deviation always more corner of primary deviation). The movements of an eye towards the affected muscle are absent or are sharply limited. There is a doubling (usually at fresh defeats) and dizziness, disappearing during the closing of one eye. Location of a subject at a sore eye is correct to estimate ability it is quite often broken (a false monocular projection, or localization). Forced position of the head — turn or its inclination in this or that party can be observed.

At paresis (but not paralysis) the nerves knowing oculomotor muscles, the deviation of an eye and restriction of its mobility are considerably less expressed. Sometimes there is no noticeable deviation at all, but there are complaints on diplopia (see).

Diverse and difficult the wedge, a picture arises in cases of simultaneous damage of several muscles on one or on both eyes.

At paralysis of a third cranial nerve the upper eyelid is lowered, an eye is rejected knaruzh and a little from top to bottom and can move only in these directions, the pupil is expanded, does not react to light, accommodation is paralyzed (a partial ophthalmoplegia).

If all three nerves — oculomotor, block and taking away are affected, then full is observed ophthalmoplegia (see) — an eye is not mobile at all. Distinguish also incomplete ophthalmoplegia — outside, at a cut outside muscles of an eye are paralyzed, but the sphincter of a pupil and a ciliary muscle are kept, and internal when only the ciliary muscle and a sphincter of a pupil are affected.

Diagnosis is based on characteristic symptomatology. It is important to establish what muscle or group of muscles is affected for what hl resort. obr. to a research of double images. For the purpose of definition of localization of the center of defeat carry out careful nevrol, inspection and electromyography (see).

Treatment consists first of all in therapy of the main disease. Carry out also electrostimulation of the affected muscle and exercise on development of mobility of eyes. At slight paresis orthoptic exercises are useful (see. Orthoptics ). Apply points with prisms to elimination of doubling, by means of partially zamatirovanny-point glazing occlusion of a sore eye or incomplete occlusion in that part of a field of vision where doubling is noted. At persistent paralyzes and paresis operation is shown. It is made not earlier than 6 — 12 months after active conservative treatment and stabilization of basic process. At inborn paralytic To. it is reasonable to operate at the age of 3 — 4 years. At paralysis of the taking-away nerve, in addition to a resection of an outside straight line and recession of an internal straight line of muscles, usually make transplantation of the tendinous and muscular rags formed from top and bottom direct muscles. Such operation quite often recovers nek-ry degree of mobility of an eye towards the paralyzed muscle.

Concomitant strabismus

Fig. 1. Position of eyes at some types of squint: 1 — meeting (the visual axis of the left eye is rejected to a nose); 2 — dispersing (the visual axis of the left eye is rejected to a temple); 3 — supravergiruyushchy (the visual axis of the left eye is rejected up).

The concomitant strabismus can be inborn and acquired; primary (without visible pathology of an eye) and secondary (developing at decrease in sight of one eye at a cataract, a cataract of a cornea, pathology of a retina, optic nerve and other diseases of an eyeglobe); constant and periodic, neakkomodatsionny (not disappearing after correction of an ametropia), partially akkomodatsionny (decreasing under the influence of correction of an ametropia) and akkomodatsionny (eliminated with correction of an ametropia); monolateral (mows one certain eye); alternating (an alternate deviation of eyes); meeting (converging) — the visual axis of one of eyes is rejected to a nose (fig. 1,7); dispersing (diverging) — the visual axis is rejected to a temple (fig. 1,2); supravergiruyushchy — a deviation of one of axes up (fig. 1,3); infravergiruyushchy — a deviation of one of axes from top to bottom.

Consensual meeting To. usually develops in the early childhood and in the beginning quite often happens periodic. Gradually there is a reorganization of all visual system of the child, edges adapts to asymmetric position of eyes. Active stopping of reaction on adequate irritation of the central site of a retina of the rejected eye leads to the fact that its images are excluded from vision. Arises funkts. scotoma (see), eliminating doubling. This scotoma disappears at switching off from sight of the fixing eye.

Disturbance of normal binocular bonds with time gains more and more strong character. In simulated conditions of division of fields of vision of both eyes sometimes there is so-called abnormal correspondence of retinas, at a cut there is a merge of the images falling on the central pole of a retina of one eye and on the paracentral site of a retina of another.

Dispersing To. meets much less often than meeting and differs in later emergence and smaller frequency of touch disturbances.

At monolateral To. function of the mowing eye resides in a condition of permanent braking that leads to sharp decrease in visual acuity of this eye — amblyopias (see). At intensive brake process the central pole loses the funkts, superiority before other sites of a retina and arises the wrong visual fixing.

At consensual To. doubling, as a rule, does not happen. Both eyes (fixing and mowing) make the movements approximately in identical volume. The movements of each eye in various directions are usually not limited or a little limited.

Fig. 2. Definition of a squint angle in degrees under the provision of a light reflex on a cornea (Girshberg's method — an explanation in the text)

The diagnosis

Inspection of the patient is begun with the anamnesis (time of emergence To., its possible reasons, the carried-out treatment, its influence on position of eyes and sight). Define visual acuity of each eye and both eyes together, without correction and with correction, character To. (monolateral or alternating) by means of test with covering of eyes, a look To. in the direction of a deviation of an eye (meeting, dispersing, vertical) and the size of a deviation. For practical purposes measurement of a corner is quite enough To. by a method of Girshberg which is carried out by the mirror ophtalmoscope. Size K. it is estimated in degrees under the provision of a light reflex on a cornea. If the reflex from the ophtalmoscope is located on edge of a pupil, then the squint angle is equal 15 ° if on the middle of an iris of the eye — 25 — 30 °, on a limb — 45 °, behind a limb — 60 ° and more (fig. 2). By means of the light device investigate a condition of solid vision. For judgment of a condition of solid vision at children of younger age use test with a prism.

Mobility of eyes is defined by movement before eyes of a sick fixating object in eight directions. At suspicion of paresis of a muscle for judgment of a condition of the oculomotor device use methods of a koordimetriya and the «provoked» diplopia.

On a synoptophore investigate ability of the visual analyzer to merge monocular images of objects. In case of bifovealny merge determine width of fusional reserves.

Fig. 3. The scheme of provisions of a fixating object on an eyeground at oftalmoskopichesky definition of a condition of visual fixing; 1 — at the correct fixing (an object in the central pole); 2 — at the wrong fixing (an object on the noncentral site of a retina).

Visual fixing is investigated (at the switched-off second eye) by means of ophtalmoscopes into which system a fixating object is entered. At the correct fixing an object is projected on the central pole, at wrong — on paracentral sites of a retina (fig. 3).

Carefully investigate optical environments (see. Oftalmoskopiya ) and eyeground (see), and also use additional methods — kampimetriya (see), test with an ocular spectrum, test using Gaydinger's phenomenon (see. Entoptichesky phenomena ), elektrofiziol, researches (see. Electrophysiology of an organ of sight ).

Treatment

Treatment is directed to recovery of solid vision, a cut returns all completeness of visual functions and at the same time provides permanent elimination of asymmetry in position of eyes.

Complex treatment consensual is standard To., a cut it consists of optical correction ametropias (see), measures for increase in visual acuity of the mowing eye (pleoptics), eye muscle operations, before - and postoperative exercises on recovery of the joint activity of both eyes (orthoptics) and their ability it is correct to estimate depth of space (stereooptics).

For the correct purpose of points to the patient To. exact definition of a refraction in the conditions of medicamentous relaxation of accommodation is necessary. Constant optical correction in combination with orthoptic exercises — the main method of treatment akkomodatsionny To., meeting at a hypermetropia and dispersing at a myopia. If at glasses wearing symmetric position of eyes steadily remains or solid vision is recovered, then at small degrees of a hypermetropia each 6 — 12 months reduce optical correction on 0,5 — 1,0 dptr and then cancel.

Treatment of an amblyopia at children of 3 — 6 years irrespective of a condition of fixing should be begun with constant switching off (occlusion) of the leading eye, a cut not less than 4 months shall be spent. The purpose of such switching off — to achieve identical visual acuity of both eyes and transition of monolateral squint to alternating. It is reasonable to combine occlusion with Avetisov (1968) method — the local «blinding» irritation light of the central pole of a retina and various visual exercises which choice is defined by age, the level of development of the child, his interests and tendencies. In the absence of effect of use of occlusion, and also in cases of the wrong visual fixing at children 6 years are more senior apply complex treatment of an amblyopia, a basis to-rogo make Kyuppers (1956) method using the negative ocular spectrum arising at illumination of a retina of a back pole of an eye with simultaneous cover of a foveolyariy zone by means of round brand and a method of the local «blinding» irritation light of the central pole of a retina. In the absence of an amblyopia or permanent increase in visual acuity higher than 0,4 orthoptic exercises which purpose to make fovealny retinokortikalny elements of both eyes dominant and to recover their joint activity are shown.

For recovery of ability to bifovealny merge carry out exercises on a synoptophore which essence consists in bystry alternate irritation of the central poles of a retina of both eyes, or apply the method based on use of two monocular ocular spectrums. In the presence of bifovealny merge develop fusional reserves on a synoptophore or (in case of symmetric position of eyes) on a stereoscope with a mirror. Exercises on development of mobility of eyes can be carried out on a synoptophore, a muskultrener or the simplified method, moving before eyes of the child any subject in the necessary directions. Similarly or by means of the Konvergentstrenera device train convergence at dispersing To.

If constant glasses wearing within 1,5 — 2 years does not eliminate To. (at so-called neakkomodatsionny To.), resort to operation (at the age of 5 — 6 years) with before - and postoperative orthoptic exercises (development of mobility of eyes, abilities to merge their fovealny images of objects, fusional ability, stereoscopic and deep sight).

The purpose of operations on muscles of an eye at consensual To. is in that by change of muscular balance, i.e. relative tensile force of muscles to receive position of eyes, symmetric or close to it, and by that to promote recovery of normal binocular functions.

Modern tactics of surgery To. it is characterized by use of such types of operation at which the muscle keeps a reliable communication with an eyeglobe. If after the first stage of operation the residual corner remains To., the second stage of operation on other muscle of the same eye or on other eye is carried out in 6 — 8 months.

At a combination of the expressed horizontal deviation of an eye with vertical it is reasonable to make horizontal muscle operation in the beginning, considering that vertical deviation can be not only a consequence of paresis of muscles, but also disturbances of balance of muscles down, a cut in primary position of an eye quite often disappears. If the vertical deviation considerable and a research of the oculomotor device indicates preferential damage of muscles of vertical action, then it is necessary to operate first of all on these muscles.

For elimination To. apply operations of two types — strengthening and weakening action of muscles.

Fig. 4. The flow diagram of a resection of a muscle at the meeting squint: 1 — the resected site of an outside direct muscle with the seam handle imposed on its cut-off edge (2); 3 — carrying out a seam through a muscle at the place of its anatomic attachment

Treat operations of the first type: a resection — shortening of a muscle by means of excision of its site at the place of an attachment to a sclera and a podshivaniye to the same place (fig. 4); a tenosuture — shortening of a muscle by formation of a fold from her sinew; a pro-raffia — movement of a sinew of a muscle of a kpereda (at interventions on direct muscles) or kzad (at interventions on oblique muscles) with formation of a fold or without it.

Fig. 5. The flow diagram of recession of a muscle at the meeting squint: 1 — the place of an attachment of an internal direct muscle; 2 — fixing of a muscle of a kzada two looplike seams.

The following operations weaken action of a muscle: free (or full) a tenotomy — crossing of a sinew of a muscle at the place of an attachment without its podshivaniye to a sclera; a tenotomy with a restrictive (safety) seam — fixing of a tenotomirovanny muscle on nek-rum distance from the place of an anatomic attachment by means of the seam passing through this place and edge of the crossed sinew; a partial tenotomy — drawing on a sinew of a muscle from the opposite edges two-three incomplete, several cuts remote from each other; recession (fig. 5) — movement of the muscle which is dissected away at the place of an attachment, a kzada (at interventions on direct muscles) or kpered (at interventions on oblique muscles) with its podshivaniye to a sclera; prolongation — lengthening of a muscle by full section of her sinew diversely and sewings together of the cut sites. Operation of a free tenotomy is made only on oblique muscles.

Prevention

Antenatal prevention To. consists in the prevention of a pre-natal infection and intoxication, toxicoses of pregnancy, a birth trauma since these factors can become a cause of infringement of an innervation of the oculomotor device at the child.

The prevention and active treatment at children of all possible reasons of damage of the nerves knowing the movements of eyes are of great importance and for post-natal prevention K.

Naiboley an available way of the prevention primary consensual To. — optical correction of ametropias at early age (1,5 — 2 years). In such way it is possible to warn at least akkomodatsionny K. Tselesoobrazno to appoint points for constant carrying at a myopia, an astigmatism and a hypermetropia in 2,5 dptr and more. Also strict observance of requirements of hygiene of sight, prevention of visual work in too short distance from eyes, reading at bad lighting is necessary, lying.

Devices for a research and treatment of squint and an amblyopia

Devices for a research and treatment of squint and an amblyopia are divided into four groups: pleoptichesky — for a research and treatment of a disbiiokulyarny amblyopia; orthoptic — for a research and treatment of disturbances of solid vision; stereooptical — for a research and recovery of deep and stereoscopic sight; group of devices for a research and treatment of the motive device of eyes.

For performing pleoptichesky treatment serve: the big bezrefleksny BO-58 ophtalmoscope with special prefixes (USSR), a pleoptofor (Switzerland) and a set from two manual ophtalmoscopes — a vizuskopa and an eytiskopa (Germany). The big bezrefleksny BO-58 ophtalmoscope is supplied with a fixating needle for installation of an ambliopichny eye in required position, a tangential scale with the darkening ball for definition of the site of the wrong fixing and a small-size bulb of an incandescence for the local «blinding» and stimulating influence by light on the central pole of a retina by Avetisov's method. Pleoptofor — the stationary ophtalmoscope with a flash gun for «dazzle» of the site of a retina with the wrong fixing and a low-voltaic lamp for the stimulating zasvet of a macula lutea. Vizuskop is intended for definition of position of the fixing site of an ambliopichny eye by means of a tangential scale, and eytiskop for treatment of an amblyopia by method of negative ocular spectrums.

From the act of sight at treatment of an amblyopia apply okklyudor to partial or full switching off of an eye. In the USSR for this purpose the okklyudor universal OKU-1 in the form of a plastic plate with a round aperture for installation of the occluding gate is issued (opaque or with an opening of a different form).

For fixing of results of treatment of an ambliopichny eye with methods of a pleoptics use the device to a training of sight at an amblyopia (USSR), a localizer proofreader (Switzerland), heyroskop (the USSR, ChSSR), a makulotester polarizing (USSR), the coordinator (Germany), a tsentrofor (Switzerland) and some other devices.

Makulotester is polarizing, the coordinator and a tsentrofor apply to transfer of the visual fixing close to central, in central. The device heyroskop represents a divider of fields of vision for development of the central simultaneous sight and solid vision.

Fig. 6. Sinotipny device: 1 — telescopes; 2 — the plane of objects; 3 — a frontomental support.

The principle of operation of orthoptic devices is based on division of fields of vision, at Krom simultaneous presentation of separate physiologically equivalent tests to the right and left eye of the patient for detection of character and extent of participation of each of eyes in solid vision is provided. There are two types of orthoptic devices — the sinotipny devices containing two telescopes for presentation of pair tests and devices with motionless tests — diploskopa of various look. The main of them are sinotipny devices; their prototype is amblioskop Uorta. These devices are used to definition of an objective and subjective squint angle, a research of a condition of muscular balance of eyes, fusional ability and mobility of eyes, development of fusional reserves, identification of borders funkts, scotomas, a research of a condition of correspondence of a retina, fight against abnormal correspondence, development of mobility of eyes, to exercises on stabilization of solid and stereoscopic vision and other parameters of solid vision. From sinotipny devices (fig. 6) the greatest distribution have a synoptophore of SINF-1 (USSR), sinoptiskop (England), a synoptophore (England, Germany). All sinotipny devices create partially simulated conditions of a research as existence of eyepieces promotes emergence of instrument accommodation. Devices with motionless test objects for a distance create the conditions which are brought closer to natural. However researches on them can be conducted only at parallel or close to parallel the provision of visual axes. Small deviations from parallelism (to 10 — 12 prismatic dioptries) are compensated by prisms. On a way of division of fields of vision such devices are divided into 5 groups: mechanical, mirror, color, polarized and raster. Eklipsny devices and devices with opaque screens dividers belong to mechanical devices. Eklipsny devices are intended for serial presentation of separate visual tests to the right and left eye with a frequency of merge of flashings. Division of fields of vision is carried out by dividers (shutters) providing the set flicker frequency. Color devices are based on property of light filters of complementary colors during the imposing at each other completely to absorb the this world falling on them, and during the mixing of the beam of light passed by them to give feeling of this world. Most often as additional use light filters of red and green colors. In the USSR it is produced in lots tsvetotest by TsT-1. Color devices are simple on a design, have big reliability, by means of these devices it is easy to inspect children of preschool age. Polarized devices differ from color in the fact that in them instead of color filters polarized are applied. A negative side of polarized devices is loss of the polarizing properties, especially under the influence of a caloradiance of lighters over time. Raster devices are based on property of optical rasters lattices to divide images for the right and left eye.

Apply sets of prisms to compensation of a squint angle, definition and development of fusional reserves, selection of means of correction with the different refracting force, prismatic rulers and biprisms. Most meet the medical requirements for the funkts, properties and service performance of a biprism. The majority of biprisms has the sizes allowing to apply them in trial frames along with corrective lenses. In the Soviet Union the biprism an oftalmokompensator of OKP-1 is issued, the refracting force a cut changes to 30 dptr.

Stereooptical devices are used to a research of solid deep vision and stereoscopic sight. For a research and recovery of solid deep vision a number of devices which prototype is Goering's device is offered. In the USSR two devices for recovery of normal solid deep vision — the stereoproofreader KBZ-1 and a stereolocalizer of LBZ-1 are issued.

Fig. 7. Oftalmokoordimetr OKM-1: 1 — projectors; 2 — turret-mounted disks; 3 — a frontomental support; 4 — the transformer (power supply); 5 — points with color filters.

Devices to a research and treatment of the motive device of eyes are used to definition funkts, conditions of an oculomotor muscle or groups of muscles by method of a koordimetriya, to a research and development of mobility and convergent movements of eyes, to control of effect of operation on oculomotor muscles. The method of a koordimetriya is carried out to the USSR by means of the device of an oftalmokoordimetr of OKM-1 (fig. 7). The Muskultrener device (USSR) is intended for a research and development of mobility of eyes. For a research and development of convergence in the USSR the device under the name «Konvergentstrener» is issued.


Bibliography: Avetisov E. S. Disbinokulyarnaya amblyopia and its treatment, M., 1968, bibliogr.; it, Concomitant strabismus, M., 1977, bibliogr.; And y z e nsh t and L. I. t and d river. Prismatic oftalmokompensator of OKP-1, Medical technician, No. 6, page 42, 1975; B of e of l about with t about c to and y E. M.’ Diagnosis and treatment of a concomitant strabismus at the present stage of knowledge, M., 1960, bibliogr.; D about l and shch ev and V. M., D and to about in A. A. and H and x and t the island and the p M. M. Devices for a research and a training of the motive device of eyes, It is new. medical instrument making, century 1, page 40, 1972; D about l and shch e in and V. M. and d river. New devices for recovery of solid deep vision, It is new. medical technicians, century 2, page 8, 1977; Noskova A. D., D about l and shch e in and V. M. and the Warsaw V. L. Devices for a research of functions of sight, It is gray. Prom-st medical technicians, century 7, p.1, M., 1975; Drank ý-m and N. I N. Functional treatment of squint at children, Kiev, 1964, bibliogr.; Sergiyevsky L. I. Concomitant strabismus and heterophorias, M., 1951, bibliogr.; Fischer E. M. Concomitant strabismus and its treatment, M., 1958; In u of i a n H. M of a. von N about about-d of e n G. To. Binocular vision and ocular motility, theory and management of strabismus, St Louis, 1974; Lang J. Strabismus, Bern u. a., 1976, Bibliogr.; Parks M. M. Ocular motility and strabismus, Hagerstown, 1975.


E. S. Avetisov; V. M. Dolbishcheva (medical tekhn.).

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