Ординатура / Офтальмология / Английские материалы / Clinical Ophthalmology A Systematic Approach 7th Edition_Kanski, Bowling_2011

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Secondary esotropia is caused by a unilateral reduction in visual acuity which interferes with or abolishes fusion; causes include cataract, optic atrophy or hypoplasia, macular scarring or retinoblastoma. Fundus examination under mydriasis is therefore essential in all children with strabismus.

Consecutive esotropia

Consecutive esotropia follows surgical overcorrection of an exodeviation. If it occurs following surgery for an intermittent exotropia in a child it should not be allowed to persist for more than 6 weeks without further intervention.

Cyclic esotropia

Cyclic esotropia is a very rare condition characterized by alternating manifest esotropia with suppression and BSV, each typically lasting 24 hours. The condition may persist for months or years and the patient may eventually develop a constant esotropia requiring surgery. Earlier correction of the full manifest angle can be successfully performed during the intermittent phase.

High myopia esotropia

Patients with high myopia may have instability of the muscle pulleys that stabilize the superior rectus and lateral rectus muscles. This results in nasal displacement of the superior rectus and inferior displacement of the lateral rectus. The possibility of this condition should be considered in high myopes with acquired esotropia; MR scan is mandatory in making the diagnosis. Treatment involves plication of the superior and lateral recti with a non-absorbable suture.

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Exotropia

Constant (early-onset) exotropia

1Presentation is often at birth.

2Signs

•Normal refraction.

•Large and constant angle.

•DVD may be present.

3Neurological anomalies are frequently present, in contrast with infantile esotropia.

4 Treatment is mainly surgical and consists of lateral rectus recession and medial rectus resection.

5Differential diagnosis is secondary exotropia which may conceal serious ocular pathology.

Intermittent exotropia

Diagnosis

1Presentation is often at around 2 years with exophoria which breaks down to exotropia under conditions of visual inattention, bright light (resulting in reflex closure of the affected eye), fatigue or ill health.

2Signs. The eyes are straight with BSV at times (Fig. 18.56A) and manifest with suppression at other times (Fig. 18.56B). Control of the squint varies with the distance of fixation and other factors such as concentration.

Fig. 18.56 Intermittent exotropia. (A) Eyes straight most of the time; (B) left exotropia under conditions of visual inattention or fatigue

(Courtesy of M Parulekar)

Classification

1Distance exotropia, in which the angle of deviation is greater for distance than near and increases further beyond 6 metres. The two types are true and simulated.

aSimulated is associated with a high AC/A ratio or ‘tenacious proximal convergence’ (TPC). The deviations for near and distance are similar when the near angle is remeasured with the patient looking through +3.00 D lenses (high AC/A controlling exodeviation) or after a period of uniocular occlusion (TPC).

bTrue. The angle for near remains significantly less than that for distance with the above tests.

2Non-specific exotropia in which control of the squint and the angle of deviation are the same for distance and near fixation.

3Near exotropia in which the deviation is greater for near fixation. It tends to occur in older children and adults and may be associated with acquired myopia or presbyopia.

Treatment

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1Spectacle correction in myopic patients may, in some cases, control the deviation by stimulating accommodation, and with it, convergence. In some cases over-minus prescription may be useful.

2Part-time occlusion of the deviating eye may improve control in some patients, and orthoptic exercises may be helpful for near exotropia.

3Surgery. Patients with effective and stable control of their intermittent exotropia are often just observed. Surgery is indicated if control is poor or is progressively deteriorating. Unilateral lateral rectus recession and medial rectus resection are generally preferred except in true distance exotropia when bilateral lateral rectus recessions are more usual. The exodeviation is rarely completely eliminated by surgery.

Sensory exotropia

Secondary (sensory) exotropia is the result of monocular or binocular visual impairment by acquired lesions, such as cataract (Fig. 18.57) or other media opacities. Treatment consists of correction of the visual deficit, if possible, followed by surgery if appropriate. A minority of patients develop intractable diplopia due to loss of fusion, even when good visual acuity is restored to both eyes and the eyes are realigned.

Fig. 18.57 Left sensory exotropia due to a mature cataract

Consecutive exotropia

Consecutive exotropia develops spontaneously in an amblyopic eye, or more frequently following surgical correction of an esodeviation. In early postoperative divergence muscle slippage must be considered. Most cases present in adult life with concerns about cosmesis and social function, and can be greatly helped by surgery. Careful evaluation of the risk of postoperative diplopia is required, although serious problems are uncommon. About 75% of patients are still well-aligned 10 years after surgery, although re-divergence may occur.

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Special syndromes

Recent genetic and neuropathological studies have shown that a group of congenital neuromuscular disorders are the result of developmental errors in the innervation of ocular and facial muscles. These conditions are now referred to as congenital cranial dysinnervation disorders (CCDD) and include Duane syndrome, Möbius syndrome, congenital fibrosis of the extraocular muscles, Marcus Gunn jaw-winking syndrome (see Ch. 1), congenital ptosis and congenital facial palsy.

Duane retraction syndrome

In Duane retraction syndrome there is failure of innervation of the lateral rectus by the 6th nerve, with anomalous innervation of the lateral rectus by fibres from the 3rd nerve. The condition is often bilateral, although frequently involvement in one eye may be very subtle. Some children have associated congenital defects such as perceptive deafness and speech disorder.

Signs

There is usually BSV in the primary position, often with a face turn. The affected eye shows the following motility defects (Figs 18.58–18.60).

1Restricted abduction, which may be complete or partial.

2Restricted adduction which is usually partial and rarely complete.

3Retraction of the globe on adduction as a result of co-contraction of the medial and lateral recti with resultant narrowing of the palpebral fissure. The degree of globe retraction may vary from gross to almost imperceptible. On attempted abduction, the palpebral fissure opens and the globe assumes its normal position.

4An up-shoot or down-shoot in adduction may be present. It has been suggested that this is a ‘bridle’ or ‘leash’ phenomenon, produced by a tight lateral rectus muscle which slips over or under the globe and produces an anomalous vertical movement of the eye. However, recent studies with MRI have shown that this is not always the case.

5Deficiency of convergence in which the affected eye remains fixed in the primary position while the unaffected eye is converging.

Fig. 18.58 Duane syndrome Huber type IIIin an infant. (A) Straight eyes in the primary position; (B) limited left abduction with widening of the left palpebral fissure;

(C) gross limitation of left adduction with narrowing of the left palpebral fissure

(Courtesy of K Nischal)

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Fig. 18.59 Duane syndrome type I in a child. (A) Straight in the primary position; (B) gross limitation of left abduction with slight widening of the left palpebral fissure;

(C) slightly limited left adduction

Fig. 18.60 Duane syndrome in an adult. (A) Straight in the primary position. (B) gross limitation of right abduction with slight widening of the right palpebral fissure and marked narrowing of the left palpebral fissure

Classification (Huber)

1Type I (see Fig. 18.59), the most common, is characterized by:

•Limited or absent abduction.

•Normal or mildly limited adduction.

•In the primary position, straight or slight esotropia.

2Type II, the least common, is characterized by:

•Limited adduction.

•Normal or mildly limited abduction.

•In primary position, straight or slight exotropia.

3Type III (see Fig. 18.58), is characterized by:

•Limited adduction and abduction.

•In the primary position, straight or slight esotropia.

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The underlying pathophysiology is similar in all three types, the differences being due to variation in the degree of anomaly in the innervation to the lateral and medial recti.

Treatment

The majority of patients with Duane syndrome do not need surgical intervention.

•Most young children maintain BSV by using an AHP to compensate for their lateral rectus weakness and surgery is only needed if

there is evidence of loss of binocular function; this may be indicated by failure to continue to use an AHP.

•In adults or children over the age of about 8 years surgery can reduce a head posture which is cosmetically unacceptable or causing neck discomfort. Surgery may also be necessary for cosmetically unacceptable up-shoots, down-shoots or severe globe retraction.

•Amblyopia, when present, is usually the result of anisometropia rather than strabismus. Unilateral or bilateral muscle recession or transposition of the vertical recti are the procedures of choice. The lateral rectus of the involved side should not be resected, as this increases retraction.

Brown syndrome

Brown syndrome is a condition involving mechanical restriction. It is usually congenital but occasionally acquired:

Classification

1Congenital

•Idiopathic.

•‘Congenital click syndrome’ where there is impaired movement of the superior oblique tendon through the trochlea.

2Acquired

•Trauma to the trochlea or superior oblique tendon.

•Inflammation of the tendon, which may be caused by rheumatoid arthritis, pansinusitis or scleritis.

Diagnosis

A left Brown syndrome has the following characteristics:

1Major signs

•Usually straight with BSV in the primary position (Fig. 18.61A).

•Limited left elevation in adduction (Fig. 18.61B).

•Limited left elevation on upgaze is common (Fig. 18.61C).

•Normal left elevation in abduction (Fig. 18.61D).

•Absence of left superior oblique overaction (Fig. 18.61E).

•Positive forced duction test on elevating the globe in adduction.

2Variable signs

•Down-shoot in adduction.

•Hypotropia in primary position.

•AHP with chin elevation and ipsilateral head tilt (Fig. 18.61F).

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(Courtesy of K Nischal)

Treatment

1Congenital cases do not usually require treatment as long as binocular function is maintained with an acceptable head posture. Spontaneous improvement is often seen towards the end of the first decade. Indications for treatment include significant primary position hypotropia, deteriorating control and/or an unacceptable head posture. The recommended procedure for congenital cases is lengthening of the superior oblique tendon.

2Acquired cases may benefit from steroids, either orally or by injection near the trochlea, together with treatment of any underlying cause.

Monocular elevator deficit

Monocular elevator palsy, sometimes also referred to as double elevator palsy, is a rare sporadic condition. It is thought to be caused either by a tight or contracted inferior rectus muscle or a hypoplastic or ineffective superior rectus muscle.

1Signs

•Profound inability to elevate one eye.

•The abnormality of upgaze persists across the horizontal plane, from abduction to adduction (Fig. 18.62).

•Orthophoria in the primary position in about one-third of cases.

•Chin elevation to obtain fusion in downgaze may be present.

2Treatment involving a base-up prism over the involved eye or surgery should be considered when fusion in the primary position has been compromised, or chin elevation is required to maintain fusion.

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Fig. 18.62 Right monoelevation deficit. (A) Defective elevation in abduction; (B) in upgaze; (C) and in adduction

Möbius syndrome

Möbius syndrome is a very rare congenital, sporadic condition.

1Systemic features

•Bilateral facial palsy which is usually asymmetrical and often incomplete, giving rise to a mask-like facial expression and problems with lid closure (Fig. 18.63B).

•Paresis of the 10th and 12th cranial nerves; the latter results in atrophy of the tongue (Fig. 18.63C). Occasionly the 5th and 8th cranial nerves are affected.

•Mild mental handicap.

•Limb anomalies.

2Ocular features

•Horizontal gaze palsy is present in 50% of cases.

•Bilateral 6th nerve palsy (Fig. 18.63A).

•Occasionally 3rd and 4th nerve palsy and ptosis.

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Fig. 18.63 Möbius syndrome. (A) Esotropia due to bilateral 6th nerve palsy; (B) defective lid closure due to facial nerve palsy; (C) atrophic tongue due to hypoglossal nerve palsy

(Courtesy of K. Nischal)

Congenital fibrosis of the extraocular muscles

Congenital fibrosis of the extraocular muscles (CFOEM) is a rare non-progressive, usually AD, disorder characterized by bilateral ptosis and restrictive external ophthalmoplegia (Fig. 18.64).

•In the primary position each eye is fixed below the horizontal by about 10°.

•The hypotropic eye may be secondarily exotropic, esotropic or neutral.

•The degree of residual horizontal movement varies from full to absent.

•Vertical movements are always severely restricted with inability to elevate the eyes above the horizontal plane.

•Absence of binocular vision and amblyopia may be present in some cases.

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Fig. 18.64 Congenital fibrosis of the extraocular muscles. (A) Bilateral ptosis and divergent strabismus; (B) compensation for severe ptosis

(Courtesy of M Parulekar)

Strabismus fixus

Strabismus fixus is a very rare condition in which both eyes are fixed by fibrous tightening of the medial recti (convergent strabismus fixus – Fig. 18.65A), or the lateral recti (divergent strabismus fixus – Fig. 18.65B).

Fig. 18.65 Strabismus fixus. (A) Convergent; (B) divergent

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