Ординатура / Офтальмология / Английские материалы / Pickwell's Binocular Vision Anomalies 5th edition_Evans_2007

PICKWELL’S BINOCULAR VISION ANOMALIES

ophthalmoplegia. Ocular myositis can cause extraocular muscle inflamma-

tion with resultant impairment of function. Kearns–Sayre ophthalmoplegia

is a mitochondrial abnormality of extraocular muscles causing progressive

external ophthalmoplegia and may be associated with cardiac defects.

Mechanical disorders

Duane’s retraction syndrome

The characteristic feature of Duane’s syndrome is retraction of the globe on

attempted adduction caused by co-contraction of the medial and lateral recti.

There may also be an elevation or depression of the affected eye. DeRespinis

et al (1993) felt that convergence insufficiency was also an invariable feature.

Duane’s retraction syndrome occurs in approximately 1 in 50 patients with

strabismus (Jampolsky 1999), is four times more common in females and

both eyes are affected in about 20% of cases. It can be familial (Finlay 2000).

Although Duane’s retraction syndrome has the characteristics of a

mechanical restriction and is usually classified thus, the underlying cause

is absent or partial development of the sixth nerve nucleus and nerve

(Jampolsky 1999).

Conventionally, the condition was classified into type A, restricted abduc-

tion and slightly defective adduction; type B, restricted abduction and

normal adduction; and type C, restricted adduction and slightly defective

abduction. However, the alternative Huber’s classification (Appendix 13 and

CD-ROM) appears to be becoming more common:

(1) Type 1: marked limitation or absence of abduction with normal or

slightly limited adduction; this is the most common type (78%; von

Noorden 1996) and is invariably associated with an absence of the

abducens nerve on the affected side (Kim & Hwang 2005).

(2) Type 2: limited or absent adduction with normal or mildly limited

abduction; this is the least common (7%) and the abducens nerve on

the affected side is present (Kim & Hwang 2005).

(3) Type 3: limitation or absence of both abduction and adduction

(Appendix 13 and CD-ROM); this type affects 15% of cases (von Noorden

1996) and is sometimes associated with an absence of the abducens

nerve on the affected side (Kim & Hwang 2005).

More complicated classifications have been proposed (Romero-Apis &

Herrera-Gonzalez 1995) but the most straightforward approach is to simply

describe the clinical characteristics. For example, ‘Duane’s syndrome of

right eye with no abduction, normal adduction, retraction on adduction’.

If this descriptive terminology is used in reports then the reader does not

have to be familiar with whatever classification the writer uses.

Jampolsky (1999) states that the condition results from a maldevelopment

or injury to developing structures (absent or partial development) of the

sixth nerve nucleus and nerve(s) in the fourth to eighth weeks of gestation.

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He argues that there is no credible evidence that the sixth nerve branches are

redirected to innervate any of the third nerve muscles. However, the medial

Table 17.7 Differential diagnosis of Brown’s syndrome and inferior

Brown’s syndrome

Inferior oblique palsy

Usually absent

ipsilateral superior oblique

May not be present.

If present, main feature

congenital cases. Head

is chin lifted, but also

tilted towards palsied side

head tilted towards

and turned towards the

involved side

uninvolved side

Various reports of

A or V patterns

common, particularly in

bilateral cases

Absent

Usually absent

Usually negative

Often present, may

be actually painful

May be present,

sometimes with

click

Marked mechanical

restriction

extraocular muscle bellies are the primary site of the disease. During this stage

it is technically a myogenic disorder but optometrists are more likely to see

the disease during the inactive, fibrotic phase, which is characterized by a

mechanical incomitancy. The condition is bilateral but can be asymmetrical,

typically with a gradual onset of diplopia. The systemic and ocular signs are

listed in Table 17.8. Rarely, the condition is associated with myasthenia

gravis. Smoking is the most important risk factor for thyroid eye disease.

The severity of visual loss in thyroid eye disease can be graded according

to the mnemonic in Table 17.9 (Cawood et al 2004). Clearly these patients

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require medical attention (Cawood et al 2004) but they should also be

monitored for compressive optic nerve damage and exposure keratitis

INCOMITANT DEVIATIONS

17

condition, which can be inherited, involving fibrosis of one or all of the

extraocular muscles (von Noorden 1996). Typically, there is downward fix-

ation of one or both eyes, with marked ptosis and chin elevation.

Supranuclear and internuclear disorders

Internuclear ophthalmoplegia

Internuclear ophthalmoplegia results from a lesion in the medial longitu-

dinal fasciculus between the third and fourth nerve nuclei. It results in poor

adduction of the eye on the affected side and abducting nystagmus in the

contralateral eye. Convergence is often, but not always, intact. Subtle cases

can be detecting by having the patient make rapid horizontal eye move-

ments to show the slowness of adduction. Bilateral internuclear ophthal-

moplegia in the young is almost always associated with multiple sclerosis.

Unilateral cases are usually due to a vascular or ischaemic lesion (Spalton

et al 1984).

Gaze palsies

Gaze palsies, arising from supranuclear disorders, do not necessarily manifest

a deviation between the two visual axes so may not meet the definition of an

incomitancy but are nonetheless included in this chapter. These can occur

due to lesions in the frontal motor centre, in the gaze centres in the pons or

in the interconnecting pathways. There is seldom diplopia and the eyes

move together in most directions of gaze. In one direction, the eyes cannot

move reflexly to take up fixation or, more rarely, cannot follow a moving

target (pursuit palsy). In lateral gaze palsy, the two eyes will not move beyond

the midline. In vertical gaze palsy, movements above and/or below the hori-

zontal are restricted. Parkinson’s disease can be associated with restrictions

of vertical gaze. New or changing gaze palsies should be referred: possible

aetiologies include neoplasms and emboli.

Parinaud’s syndrome

Parinaud’s syndrome is also known as dorsal midbrain syndrome. It is char-

acterized by: gaze palsy for elevation or depression or both for saccades

and later pursuit, convergence retraction nystagmus, upper eyelid retraction,

large pupils with light-near dissociation, and papilloedema. Causes include

tumours of the pineal gland and vascular accidents or trauma.

Skew deviation

This is a transient vertical divergence where one eye is elevated and the other

is depressed. The deviation may be comitant or may vary in different posi-

tions of gaze. The main differential diagnosis is from acquired fourth nerve

palsy, which will be associated with a cyclodeviation. Cyclodeviations may

(von Noorden 1996, p 415) or may not (Lee 1999) be present with skew devi-

ation. Skew deviation can be intermittent but usually occurs in association

with brain stem, cerebellar, or vestibular disease (Lee 1999). Skew deviation

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is usually accompanied by binocular torsion, torticollis, and a tilt in the

PICKWELL’S BINOCULAR VISION ANOMALIES

subjective visual vertical; this constellation of findings has been termed the

ocular tilt reaction (Brodsky et al 2006).

Other disorders

Pattern deviations (alphabet patterns; pattern strabismus;

A- and V-syndromes)

Quite commonly, cases are encountered in which the patient appears to be

fairly comitant on motility testing in the six cardinal positions of gaze but

the horizontal deviation is seen to increase or decrease with the eyes in

upor down-gaze. The simplest examples of these cases are the A-syndrome,

in which the eyes are relatively more convergent in up-gaze, and the

V-syndrome, in which the eyes are relatively more convergent in down-

gaze. V-syndrome is about twice as common as A-syndrome (von Noorden

1996). An estimated one in five patients with strabismus may be expected

to have an A or V pattern (von Noorden 1996, p 383; Biglan 1999), and

subtle variants of the conditions are very common in ‘normal’ heteropho-

ria. Von Noorden (1996, pp 376–383) discussed the aetiology of the con-

dition, concluding that several factors play a role, including dysfunction

of the oblique muscles and various anatomical factors, including the

configuration and rotation of the orbit (Biglan 1999).

Both A- and V-syndromes can be present in patients with exoor eso-

deviations. For example, in A esotropia the esotropia increases in up-gaze and

decreases in down-gaze. In V exotropia the deviation increases in up-gaze

and reduces in down-gaze. Other variants also exist, although they are less

common. For example, in X syndrome the eyes may be straight in the pri-

mary position and exotropic in up-gaze and down-gaze. Other variants

include Y pattern and λ pattern. It is not surprising that the generic terms

‘pattern strabismus’ or ‘alphabetic pattern’ have been coined.

These patterns may be present as congenital anomalies or may accompany

an acquired strabismus, particularly where the oblique muscles are affected.

Anomalous head postures are common. The presence of A or V patterns can

improve the prognosis because binocular single vision may be developed

or maintained in upor down-gaze. However, most pattern deviations do

not require treatment (Ansons & Davis 2001, p 336). When treatment is

required, some authors have found success with oblique prisms but others

do not advocate this approach (von Noorden 1996, pp 385–386). Surgical

approaches are also available (von Noorden 1996, pp 383–389; Biglan

1999, pp 209–214).

Pattern deviations can be diagnosed with cover testing in upand down-

gaze and, more accurately, with a Hess or Lees screen. Von Noorden (1996,

p 384) suggested criteria for diagnosis: a V pattern with a difference of 15

or more from upto down-gaze and an A pattern with a difference of 10 .

Several disorders are commonly associated with pattern deviations: infan-

tile esotropia syndrome, Duane’s retraction syndrome, Brown’s syndrome,

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acquired fourth nerve palsy and thyroid eye disease (Ansons & Davis 2001,

pp 334–335).

INCOMITANT DEVIATIONS

17

Superior oblique myokymia

Benign superior oblique myokymia is an episodic, small-amplitude, nystag-

moid intorsion and depression of one eye, accompanied by visual shim-

mer and oscillopsia (Case study 17.1). The condition was originally called

unilateral rotary nystagmus (Plager 1999). The onset is in adulthood and the

symptoms are ‘most annoying’, while the ‘diagnosis is often missed’ (von

Noorden 1996, p 456). Episodes usually last from 20 seconds to several

minutes and can be triggered by physical activity (von Noorden 1996,

p 456) and fatigue and stress (Plager 1999). The prevalence of this condi-

tion does not appear to be quoted in the literature.

Superior oblique myokymia is usually benign but there have been at

least two cases of association with a posterior fossa tumour (von Noorden

1996). Plager (1999) felt that neuroimaging was unnecessary, unless there

were other neurological complaints.

Although the precise aetiology is unclear (von Noorden 1996, p 456),

superior oblique myokymia may be the result of regeneration (Plager 1999)

after prior clinical or subclinical injury to the trochlear nerve (Mehta &

Demer 1994). Medical treatments have been found, as with Case study 17.1,

to be generally disappointing (von Noorden 1996, p 456; Plager 1999);

although promising results from oral gabapentin have been reported in

two cases (Tomsak et al 2002). Surgical approaches are sometimes success-

ful, although second operations may be required (von Noorden 1996).

Inferior oblique overaction

Inferior oblique overaction is a common sequel to an early onset interrup-

tion to binocularity, typically infantile esotropia syndrome (Koc et al

2003, Brodsky 2005). It is often accompanied by latent nystagmus and/or

dissociated vertical deviation.

Management

Considerable attention has been given in this chapter to the diagnosis of

conditions requiring medical attention. This is obviously the first priority

in the interest of the patient. The number of patients who have incomi-

tant deviations as an early sign of disease requiring urgent medical atten-

tion is not large, and many of them will take medical advice in the first

place. This means that the largest number of incomitant deviations likely

to be seen in primary eyecare practice will be long-standing deviations,

and most of these will already have had medical attention. Therefore, the

question that arises is whether there is anything further that can be done

in these long-standing cases. Incomitant deviations do not respond at all

well to eye exercises. Very occasionally, congenital conditions in children

may be helped by exercises to extend the area of the binocular field over

which there is binocular vision, or to re-establish it when it has broken

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down due to general ill health. In the latter case, the patient may suddenly

PICKWELL’S BINOCULAR VISION ANOMALIES

CASE STUDY 17.1 Ref. F6155

BACKGROUND: 47-year-old businessman referred by neurologist to

optometrist to investigate vertical diplopia and photosensitivity. Possible history

of binocular anomaly at age 9 years.

SYMPTOMS: For the last 18 months, he has experienced momentary vertical

diplopia at some time most days; people who are with him do not notice any

abnormalities. Headaches, particularly with office work. Reading is blurred,

unstable and tiring; patient has given up reading for pleasure. Two

ophthalmologists diagnosed superior oblique myokymia: one discharged

patient, the other tried medical treatment, to no avail.

CLINICAL FINDINGS: Minimal myopia and early presbyopia. At distance and

near, dissociation testing revealed 2 R hyperphoria with same aligning prism on

Mallett unit. Motility appeared normal but Lees screen revealed mild underaction

of right superior oblique muscle, confirmed by Scobee’s three-step test (Parks

inconclusive) and double Maddox rod test.

MANAGEMENT: Prescribed distance spectacles and near spectacles, both with

vertical prism.

FOLLOW-UP 5 WEEKS LATER: Virtually no vertical diplopia or headaches,

reading much easier.

COMMENT: It seems likely that the patient had a long-standing superior

oblique paresis, with secondary superior oblique myokymia. The comitancy had

spread so that it was possible to correct the vertical deviation with a prism that

it is established that the general condition has cleared.

Patients with strabismus with an onset in childhood will have suppression

or HARC that prevents diplopia over most of the visual field. There may be

some diplopia in one peripheral part of the motor field. Usually it is better not

to disturb this adapted or partially adapted state. If one eye has been neglected

or has had a blurred image for many years, correcting the refractive error can

produce troublesome diplopia. It may be better to give a balancing lens or a

blurring lens to maintain the status quo. In some cases, correction may be

appropriate, particularly in children, if it is likely that some binocular vision

can be restored, perhaps with relieving prisms. However, this is a difficult pro-

cedure and should only be attempted with great caution. Once diplopia is cre-

ated, it is difficult for the patient to revert to suppression. Very occasionally,

the sensory adaptation in these incomitant deviations seems to break down

spontaneously and we are presented with a patient complaining of diplopia

and a long-standing deviation not due to recently acquired pathology. The

management of intractable diplopia is discussed on page 227.

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It has been suggested that some patients with acquired incomitant devi-

ations benefit from monovision, where each eye is given its own ‘domain’