Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

5.Essential blepharo spasm

6.Exotropia20

Acquired esotropia

Acquired non paralytic esotropia is commonest type of esodeviation seen in children. They have been classified in different ways -

1.On clinical presentation

2.Etiological basis

The second seems to be better than the first. It divides acquired esotropia into - (i) Primary

(ii) Secondary and consecutive (They are far less in number) The primary or the common variety is divided into -

(a) Accommodative

(b) Non accommodative

(a) Accommodative esotropia can be fully accommodative with normal Ac/A or high Ac/A ratio. However many of the accommodational esotropias may be partially accommodative.

(b) Non accommodative esotropia can be

Basic type

Convergence excess type Esotropia in myopia Microtropia

Noorden21 1990 gave a comprehensive classification

divergent squint

Basic Convergence Myopic

Excess

Accommodative esotropia

Accommodative esotropia is one of the commonest forms of ocular deviation seen in children. It’s diagnosis is simple and treatment is effective. This is a type of manifest squint that can be treated mostly by optical methods. However those who present late may have to undergo surgery and anti amblyopic treatment.

Characteristics of fully accommodative esotropia

1.Age of onset—It is seen between six month to six years. Average age of presentation being 2½ years.

2.Heredity—The condition has strong hereditary background. It may be present in parents, near relatives or in siblings.

3.Deviation—Ocular deviation is

(i) Uniocular

(ii) Variable greater for near than distance

(iii) Intermittency—The child may have intermittent esotropia that may become constant.

(iv) Angle of deviation is not very large, it ranges between 20PD to 45 PD. (v) The child does not alternate.

(vi) There is no cross fixation.

4.Amblyopia is common but not deep.

5.Error of refraction is typically hypermetropic ranging between +4D and +7D. The squinting eye is more hypermetropic than the other.

6.AC/A is normal i.e. between 3D-5D.

7.Near distance relationship is either normal or when different it is not more than 10 PD.

8.The deviation is fully corrected by spectacles and the eyes remain straight, hence do not require surgery.

9.Binocularity is present due to anomalous retinal correspondence.

10.Children with higher hypermetropia more than 8D generally do not develop accommodative squint.22 They have bilateral amblyopia. Most probably they give up accommodation. These children do not improve with glasses.23

11.Spontaneous recovery with reduction of hypermetropia is possible, the condition may pass into partially accommodative or non accommodative squint.24

12.There may be associated DVD or inferior oblique over action.

13.Binocular single vision is possible for far and near when hypermetropia is fully corrected.

Etiology of accommodative esotropia

There are two factors that lead to accommodative esotropia i.e.

1.Uncorrected hypermetropia

2.Abnormally high Ac/A ratio.

1. Hypermetropia. An emmetropic child needs no accommodation for distance vision, a myopic eye becomes worse by accommodation. It is only hypermetropia that is relieved by accommodation.

These children with accommodative esotropia generally have an uncorrected hypermetropia of moderate degree. The child uses excessive accommodation to overcome this

hypermetropia. This by itself does not explain the complete mechanism. The second part of the mechanism is in sufficiency of fusional divergence. So long fusional divergence is sufficient, the child does not develop manifest squint. An occassional esophoria may result. This may lead to intermittent esotropia. Once the fusional divergence breaks down esotropia results.

2. Abnormally high Ac/A ratio. Normal Ac/A ratio is 3D-5D. It can be measured by following methods25 :

1.Heterophoria method

2.Gradient method

3.Graphic method.

Management of accommodative esotropia

Optical

A.The first line of management is prescription of hypermetropic correction for constant use with correction of associated astigmatism. Glasses should be prescribed after refraction under 1% atropine only. Children under four years are given full cycloplegic correction. If a child older than four years is prescribed full cycloplegic correction, the child may not tolerate it. They are generally given as much plus lens possible that keeps the eyes straight and vision clear. The power of the plus lenses may be required to be reduced over years.

B.Fully hypermetropic correction for distance generally keeps the eyes straight for distance as well as near. In some children there is some esodeviation for near. In such situation the first step is to see if the distant correction has been fully corrected or not. This should follow repeat refraction under atropine. If it is found that the child has been given full correction at the first instance, the second step is to give bifocals. The near power should be just sufficient to keep the near axis straight. The best bifocals for children are executive type where the junction of far and near correction pass across the pupil.

Miotics

The next alternative is use of miotic. All children do not respond equally well to miotic therapy. About 10% may not improve, some may show poorer result than bifocals.

The beneficial effect of miotics should be weighed against the local and systemic side effects of miotics.

Orthoptic treatment

Orthoptic treatment is recommended in older children with hypermetropia less than

+3D.

Surgery

Surgery is not required for horizontal deviation but DVD and inferior oblique over action requires surgical management.

Accommodative esotropia with high Ac/A

In case of fully accommodative esotropia Ac/A is within normal limits. There are some children who have high Ac/A. They have more esodeviation for near than distance. Some may

not even squint for distance.26 They may have various types of error of refraction that range between low hypermetropia to mild myopia, even emmetropia in some cases. Chances of high Ac/A are more when cycloplegic refraction shows low hypermetropia, myopia or emmetropia. High hypermetropes have more or less normal Ac/A. The condition is not fully corrected by glasses, some esotropia is left uncorrected.

Management consists of correction of any error of refraction and improvement of vision for distance. Adding plus lenses for near deviation either as bifocal or clipon near correction. While adding near correction minimal addition that corrects near deviation is prescribed. The bifocal should be executive type, the upper border of the near correction should divide the pupil in two equal parts horizontally. Non correction of near deviation by bifocals is strong indication of non accommodative factor that can be corrected by surgery only.

Miotics can also be given for near esodeviation.

Partial occlusion and orthoptic exercises help to overcome amblyopia and help increase amplitude of divergence fusion.

Comparison between infantile esotropia and accommodative esotropia

Partially accommodative esotropia

Partially accommodative esotropia is a mixture of accommodative as well as non accommodative esotropia.

There is always some esodeviation left after full spectacle correction of hypermetropia even with bifocals and/or miotics.

There are two possible explanation for the condition :

1.The child was initially an infantile esotrope to which accommodative element has been added as the child ages. There may be increase in hypermetropia. Final hypermetropic refraction is more than initial hypermetropia.

2.The child had accommodative esotropia to which non accommodative element has been added due to decompensation. Generally there is hypertrophy of medial rectus or conjunctiva on the medial side.

The residual esodeviation is constant, it is same for near and distance. It is associated with amblyopia.

Treatment27

Treatment consists of surgery for esodeviation and continuation of glasses post operatively.

Non accommodative acquired esotropias

There are three types of these esotropias28

1.Basic type

2.Convergence excess

3.Esotropia in myopia

1.Basic type non accommodative acquired esotropias : Characteristics :

1.This generally manifests after 6 months of age and limited to childhood.

2.It is unilateral.

3.Vision is less in squinting eye.

4.There is hardly any error of refraction.

5.There is no accommodative factor.

6.Deviation is almost same for distance and near.

7.To begin with, the deviation is small that may become very large with age.

8.Being monocular, the squinting eye develops amblyopia which requires proper management.

9.Glasses or miotics do not abolish squint. However associated error of refraction should be treated when present.

10.Surgical treatment is definitive treatment. Commonest surgery is bi-medial recession with conjunctival recession.

2.Convergence excess esotropia :

Characteristics :

1.Seen between 2 to 3 years of age

2.Deviation for distance is minimal

3.Near deviation is between 20° to 40°.

4.The child may have low grade hypermetropia or may be emmetropic.

5.There is no accommodative factor responsible for deviation.

6.Surgery is the treatment of choice.

Other esotropias :

1.Microtropia

2.Esotropia in myopia

3.Cyclic esotropia

4.Nystagmus blocking esotropia

5.Consecutive esotropia

6.Secondary esotropia

7.Esotropia in DVD and inferior oblique over action

8.Acute esotropia

1. Microtropia29,30,31. Commonest form of presentation is small degree of esotropia, occasionally it may present as exotropia, hypertropia and rarely as orthophoric, hence it is also called micro-strabismus. The fixation is restricted to non squinting eye, hence it is called mono fixation syndrome.

Characteristics :

1. It is a permanent condition.

—Surgical correction of above

3.Angle of deviation is small—8 to 10 PD.

4.Mild amblyopia is common even in spite of small angle of deviation.

5.Central fusion is absent.

6.There is facultative macular scotoma that is made obvious on Worth four dot test and Bagolinies test.

7.Cover uncover may show small esotropia that increases during prism cover test.

8.Sometime 4 prism diopter base out test may be positive.

9.The condition is more common in anisometropic amblyopia.

10.There is para foveal fixation, peripheral fusion.

11.Harmonious ARC.

12.Almost normal stereo acuity.

Management :

Mono-fixation syndrome can be treated by orthoptic treatment or surgery. Microtropia persists even after orthoptic treatment, it may strength peripheral fusion.

2. Esotropia in myopia. Myopic children have good near vision and poor distant vision. In small children onset and progress of myopia is so gradual that the child does not realize his poor distant vision unless pointed out.

In moderate uncorrected myopia, the near vision is either within near point or near to it. Accommodation worsens myopia. The child is only left with one option i.e. to converge to have clear vision. The child may altogether give up any effort for clear distant binocularity, retain binocularity for near and convergent squint.

In older children who have acquired myopia, fusional deficiency of divergence enhances convergence and esotropia.

The treatment consists of correction of myopia and surgical correction of esodeviation.

3. Cyclic esotropia32,33. This is an uncommon esotropia of unexplained origin. Generally seen in children between three to four years. It is most often mistaken as intermittent esotropia. There is a fixed cycle of esotropia and orthophoria appearing with a fixed gap that ranges between 24 hours to 96 hours. Typical presentation is that the child has a large angle esotropia for a day or two followed by a gap of same duration of orthophoria (non squinting days). Such episodic attacks last for few months to two years before the condition becomes constant for all days. Initially there is no amblyopia, amblyopia develops when the squint becomes constant. See chapter 17 page 608.

Treatment consists of treatment of amblyopia when present and surgical correction.

4.Nystagmus blocking esotropia. Children with congenital esotropia are known to have nystagmus either as manifest nystagmus or manifest latent nystagmus independent of esotropia. In some children who have nystagmus in straight eye, the nystagmus disappears if the eye is adducted. This is called nystagmus blocking esotropia. This is often confused as infantile esotropia with nystagmus. The treatment is recession of both medial recti with myopexy behind the equator. See page 633.

5.Consecutive esotropia. It is common for a child to develop small degree esotropia following surgery for exodeviation. This is transient and associated with diplopia. However if esotropia persists after few weeks, it should be evaluated and treated. Possibility of amblyopia should be kept in mind and managed.

EXOTROPIA34

Exotropia is manifest deviation of any of the eyes outward.

Normal position of the eye at rest is slight exodeviation. This is so small that it is taken as physiological and the eye is considered to be orthophoric.

General features of exotropia-

1.Exotropia can be congenital or acquired.

2.It can be uniocular or alternate.

3.To begin with most of the exotropias are exophoric. However an eye can be exotropic without going through the phase of exophoria.

4.It can be equal for far and near, it can be greater for distance and lesser for near or vice versa.

5.The angle of deviation may increase with passage of time.

6.Exotropias are generally large degree of deviation.

7.Associated errors of refraction are generally of small degree and there is no predilection for any specific type of error of refraction.

8.Suppression is common but amblyopia is less frequent.

9.An exotropic eye generally have poor adduction that may be diagnosed as medial rectus paresis. In such cases adduction can be demonstrated by patching the other eye for few hours.

10.Exotropia is more common among girls. There may be a hereditary basis.

There are various modes of development of exotropia. Commonest mode is as follows :

Orthophoria—Exophoria—Intermittent exotropia—Constant exotropia—Increase in exotropia.

The other less frequent possibility is esotropia passing into straight eye and then exotropia.

The third possibility is consecutive exotropia where there is surgical over correction of esotropia.

Lastly, secondary exotropia develops in eyes that have long standing poor vision with amblyopia in one eye due to - anisometropia, uncorrected unilateral aphakia, unilateral cataract, corneal opacity, macular scar, optic atrophy.

It has been observed that uniocular loss of vision under five years of age may produce both esotropia or exotropia. Esotropia is more common. After five years chances of exotropia is far more than esotropia.35

Various combinations of exotropia

Classification of exotropia

An exotropia is called essential when it is

1.Primary concomitant

2.There is no binocularity

3.There is no neurological defect

4.There is no anatomical defect

5.There is no detectable cause of diminished vision i.e. opacities in media, defect in conduction, unilateral high error of refraction.

Pseudo exotropia

In this case the eye/eyes seem to diverge due to any of the following causes-

Telecanthus, positive angle kappa, temporal drag of the macula as in retinopathy of prematurity.

On Hirschberg test, the corneal light reflex is central. The cover test does not show any deviation. Pseudo exotropia unlike pseudo esotropia does not disappear with age.

Congenital exotropia33,35,36

Incidence of congenital exotropia is less than congenital esotropia. The exotropia becomes obvious by two months of age. The angle of deviation is constant for distance as well as near. The deviation ranges between 40 to 80 PD. There is no cross fixation. The child has homonymous fixation i.e. the child fixes right field by right eye and left field by left eye. This increases temporal field of vision. Alternation is common hence amblyopia is less frequent. DVD and nystagmus may be seen in some cases. Error of refraction when present are of small degree.

Management

The aim of the treatment is to bring the alignment within 10 PD before two years. Surgery is the treatment of choice. However if there is error of refraction more than 3D hypermetropia or 2D myopia, it should be corrected before surgery.

Primary acquired exotropia Intermittent exotropia37

Intermittent exotropia is the commonest type of exotropia and second most common squint in children. The child has exotropia especially when the child is tired or daydreaming. A child may be brought with history of exotropia but on initial examination he may seem to be orthophoric and requires repeated examination in the same sitting to unmask the deviation. Sometimes an intermittent exotropia may resolve spontaneously.37

In about 75% cases the deviation does not change over years but in a small group of cases the deviation may increase. Generally the condition becomes manifest by four to five years of age but not before two years.

The child generally has good vision or small error of refraction with normal binocularity in primary position. When the eyes are straight there is good stereopsis, bifoveal fusion without suppression. Facultative suppression develops only when the eye deviates. This prevents diplopia.

The child himself may not be aware of deviation, looking at a mirror corrects the deviation. However presence of exotropia may become obvious in a photograph. Some children may complain of blurred vision and/or asthenopia. The parents may complain that the child closes one eye in bright light. This phenomenon may persist even after surgical correction.

Both A and V pattern are met with, however V pattern is more common in intermittent exotropia. DVD and nystagmus are less frequent than in esotropia.

Clinically it can be divided into :

1.Divergence excess exotropia

2.Convergence deficient exotropia

3.Basic exotropia

4.Pseudo divergence

Divergence excess type of exotropia

The exotropia is more when measured for distance. It is better to measure distant deviation when the child is fixing beyond usual six meters. The difference between far and near is more than 15 PD. The near deviation may occasionally be exophoria. If the accommodation is relaxed by putting +3.00D sph. in front of each eye and near distance is remeasured, there is generally no difference from the original deviation.

Convergence deficient exotropia-

The near exotropia is more than distant exotropia at least by 15 PD with full correction. It may be present with diminished accommodation as in myopes who need not accommodate or rarely in hypermetropes more than 6 Dsph who give up accommodation. They may have low Ac/A ratio.

Basic exotropia

Here exotropia for far and near are equal or with in 15 PD.

Pseudo divergence (Simulated divergence excess)

The distant exotropia is greater by 15 PD than near as in divergence excess type when examined for first time. This difference decreases to less than 10 PD after half an hours patching of one eye. The measurement should be taken immediately before fusion develops. The other diagnostic test is to measure near deviation with +3.00 Dsph in front of both eyes. The near deviation becomes as much as or greater than distant deviation. The causes of this phenomenon is not understood.

Management

Treatment is indicated only if the intermittency is replaced by constant exotropia. The mode of management depends upon age of the patient and severity of symptoms.

Treatment consist of 1. Optical

(a) Glasses for any significant error of refraction. Myopia is fully corrected and hypermetropia is under corrected.