EYE MOVEMENT DISORDER Ophthalmology

Collected by : Tha'er Ahmad Alajou

APRIL 10, 2020

• Eye movements may be abnormal because there is:

• 1. abnormal position of eyes.

• 2. reduced range of eye movements.

• 3. abnormality in character of eye movements.

Extraocular Muscles actions (1°)

Medial rectus

Adduction

Lateral rectus

Abduction

Inferior rectus

Depression

Superior rectus

Elevation

Superior oblique

Intorsion

Inferior oblique

Extorsion

Innervation of EOM

Superior division of Oculomotor (3rd ) nerve

Levator palpebrae and Superior rectus muscles.

Inferior division of Oculomotor nerve

Medial rectus, Inferior rectus and Inferior oblique muscles.

4th nerve (Trochlear nerve)

Superior oblique.

6th nerve (Abducens nerve)

Lateral rectus.

• Strabismus (aka squint/ crooked eye) is a generic term applied to all those conditions in which visual axes assume a position relative to each other

different from that conforming to physiological conditions.

• Strabismus = squint : is deviation of an eye’s visual axis from it’s normal

• Eso : inward Exo: outward

• Hyper: superiorly Hypo: inferiorly

• Tropia : always deviated ( manifest squint)

• Phoria : sometimes deviated (latent squint)

• Binocular single vision : both eyes are directed towards the same object of regard ,their movements are coordinated so that the retinal images of an

object fall on corresponding points of each retina, these images are fused

centrally, so that they are interpreted by the brain as a single image.

• stereopsis : Because each eye views an object from a different angle this permits a three-dimensional percept to be constructed.

• The development of stereopsis requires that eye movements and visual

alignment are coordinated over approximately the first 5 years of life.

• Binocular single vision and stereopsis afford certain advantages to

the individual:

• They increase the field of vision.

• They eliminate the blind spot, since the blind spot of one eye falls in the seeing

field of the other.

• They provide a binocular acuity, which is greater than monocular acuity.

• Stereopsis provides depth perception and estimation of distance.

• If the visual axes of the two eyes are not aligned, binocular single vision is not

possible. This results in:

1. Diplopia : An object is seen to be in two different places.

2. Visual confusion : Two separate and different objects appear to be at the same

point

Eye movement disorders :

1. non-paralytic squint (concomitant)

Deviation is equal in all of gaze and movement of both eyes are full ( there is no

paresis ) but only one eye is directed towards the fixated target.

It could be : monocular , alternating or intermittent

Angle of deviation is constant and unrelated to the direction of gaze

The common squint that is seen in childhood and usually begins in infancy , up to 8-10 years

Etiology : may developed on normal child with normal eyes so the cause is obscure or idiopathic

it thought to be caused by an abnormality in the central coordination of eye

movements

diplopia is absent.

Amblyopia : is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together.

Amblyopia only occurs in unilateral strabismus

Amblyopia is reversible before 7-8 years

examination and investigation

1. First the patient is observed for features that may simulate a squint.

These include: epicanthus (a crescentic fold of skin on the side of the nose that

incompletely covers the inner canthus) ; hirschberg test to to detect pseudo

squint

2. Determination of acuity

3. Determination of any refractive error .

4. Detection of any abnormality in eye movement (H shape).

5. Cover uncover test

6. Careful examination of the eyes to exclude opacities of the cornea, lens or

vitreous and • abnormalities of the retina or optic disc.

Cover – uncover test

Pseudo strabismus

In young infant, strabismus must be differentiated from more common pseudo

strabismus

Pseudoesotropia as a result of a broad bridge of the nose, this is not a real eye

crossing .

Non paralytic squint with no associated ocular disease is treated

as follows:

Any significant refractive error is first corrected with glasses.

Surgical intervention to realign the eyes may be required for functional reasons

(to restore or establish binocular single vision) or for cosmetic reasons (to

improve appearance and prevent a child being singled out at school)

2. Paralytic squint (incomitant squint)

Angle of deviation is different in different position of gaze.

Extraocular movement are not full so there is under action of one or more of

the eye muscles due to a nerve palsy or mechanical restriction of the

muscles

Neurogenic :

1. Congenital hypoplasia/ absence of 3rd/ 6th nerve nucleus.

2. Meningitis/ Encephalitis/ Syphilis.

3. Brain tumors involving 3rd/6th nerve nucleus.

4. Vascular lesions (Hypertension/DM/ Atherosclerosis)

5. Head injury involving nerve trunks.

6. Demyelination in MS (Multiple sclerosis).

Neuromuscular junction

Myasthenia Gravis.

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History and examination:

The patient usually complains of diplopia, there may be an abnormal head

posture to compensate for the inability of the eye to move in a particular

direction.

Sixth nerve palsy results in failure of abduction of the eye.

Fourth nerve palsy results in defective depression of the eye when attempted in adduction ,, usually the damage is bilateral due to head trauma (

concussion )

Third nerve palsy 1. Failure of adduction , elevation and depression of the eye

2. Ptosis

3. In some cases dilated pupil due to involvement of autonomic fibers pupil

involvement here can be a feature of extrinsic compression of the nerve.

4. Posterior communicating artery aneurysm is an important cause of sudden onset

of 3rd CN. palsy with pupillary dilatation.

Common in young adults (come with severe headache & sudden onset squint )

Treatment :

An isolated nerve palsy is related to coexistent systemic disease , if

posterior communicating aneurysm is suspected, patient must be sent for

neurosurgical review and angiography.

The most common cause of palsy is microvascular disease of a peripheral cranial

nerve, associated with diabetes or hypertension.

The nerve function often recovers over months. Especially in old ones.

Disease in the cavernous sinus may also be the cause of multiple nerve palsies

such as 3rd , 4th and 6th

Diplopia can be helped by fitting prisms to the patient ’ s glasses, which realign

the retinal images.

If eye movements fail to improve spontaneously then surgical intervention may be

required..

Disease of the extraocular muscles

1. Dysthyroid eye disease (Grave’s disease)

2. Myasthenia gravis :

Pathogenesis

caused by the development of antibodies to the acetylcholine receptors of

striated muscle.

It affects females more than males 15-50 years

Some 40% of patients may show involvement of the extraocular muscles

only

Symptoms and signs:

Variation in clinical signs and symptoms over days to weeks, with

fatigability, is the hallmark of myasthenia

Variable diplopia and variable ptosis may be present

Diagnostic tests :

Confirmed by :

1. electromyography

2. By determining whether an injection of neostigmine or edrophonium

(cholinesterase antagonists) temporarily restores normal muscle

movement

Treatment :

Patients are treated in collaboration with a neurologist , with neostigmine .

Systemic steroids and surgical removal of the thymus

Multiple choice questions 1. Match the eye muscle to the nerve.

a Lateral rectus.

b Superior rectus.

c Medial rectus.

d Inferior rectus.

e Superior oblique.

f Inferior oblique.

i Third nerve.

ii Fourth nerve.

iii Sixth nerve.

2. Which of the following statements are true?

a In a non - paralytic strabismus the movement of the eyes is reduced.

b In a non - paralytic strabismus the angle of deviation is unrelated to the

direction of gaze.

c In a paralytic strabismus, the eye movement is reduced.

d Nystagmus refers to an oscillating movement of the eyes.

e In a horizontal gaze palsy the patient is unable to look to one side.

3. Amblyopia

a Refers to a developmental reduction in visual acuity.

b May be caused by Duane ’ s syndrome.

c May be caused by a previously unidentifi ed difference in refractive correction

between the two eyes.

d May be caused by a squint.

e May be treated by patching the amblyopic eye.

4. Nerve palsies affecting the third, fourth on sixth cranial nerves may be

seen in

a Orbital disease.

b Raised intracranial pressure.

c Ischaemia of the cerebral cortex.

d Systemic infl ammatory disease.

e Trauma.

5. Internuclear ophthalmoplegia

a Is caused by a lesion of the medial longitudinal fasciculus.

b Manifests as a reduced adduction and contralateral nystagmus in the

abducting eye.

c Is manifested by a failure of the eye to elevate in adduction.

d May be caused by demyelination.

e Requires surgical treatment.