Strabismus

Mohamad Abdelzaher

MSc

The reason why so few good books are written is that so few people who can write know anything.

Walter Bagehot

Anatomy of EOMs

• 4 recti• 2 obliques

• Origin

• Annulus of Zinn

• Course of EOMs

• Insertion of recti:

Spiral of Tilluax

• Insertion of obliques

• Nerve Supply:

III nerve: all except,

L6 SO4

• Rotation of the eye:

center of rotation 12-13 mm behind corneaAdduction (Z)

Abduction (Z)

Elevation (X)

Depression (X)

Intorsion (Y)

Extorsion (Y)

• Action of EOMs

• Orbital vs Visual axes * Action of right SR

• Action of right SO

• Regarding the torsion movement:

“There is only on (I) in the sentence”

SO -------- Intorsion

IO --------- Extorsion

SR -------- Intorsion

IR --------- Extorsion

• Action of EOMs

• Binocular movement

• Diagnostic positions of gaze

Binocular Vision

Pseudo Strabismus

• Pseudo eso• Pseudo exo• Pseudo hyper• Pseudo hypo

CORNEAL LIGHT REFLEX

• Epicanthus

• Ptosis

Heterophoria• Definition “binocular vision”

• Types• Aetiology• Clinical picture

- compesated vs decompensated

-- how to dissociate binocular vision:

1) cover test

2) Maddox rod

3) Maddox wing

Cover – Uncover test

Orthophoria, normal

No complaints, asymptomatic

Cover test

Cover – Uncover test

Esophoria, abnormal, common

Only seen when eye is covered

Often asymptomatic, no complaints

Note OS does not move.

Cover – Uncover test

Exophoria, abnormal, common

Only seen when eye is covered

Note OS does not move

Often asymptomatic, no complaints.

• Maddox rod

• Maddox wing

• Treatment:- Indications- Lines:

1) correct refractive error

2) orthoptic exercise: pencil-nose exercise

exercising prism

synoptophore

3) Relieving prisms

4) Surgery

• Exercising prismse.g. base-out prism to exercise exophoria

• synoptophore

Paralytic squint• Definition “angle of deviation”

• Aetiology: LMNL - nuclear

- nerve

- muscle

1) Congenital2) Traumatic3) Inflammatory4) Vascular5) Neoplastic6) Metabolic7) Toxic

• Symptoms:- Diplopia- Ocular deviation- Abnormal head posture

• Signs:1) Ocular deviation: “Hering law” “Angle of deviation”

2) Limitation of movement “9 diagnostic positions of gaze”

3) Binocular diplopia - homonymous

- heteronymous

4) Diplopia chart

• Complications:

Direct antagonist ------------- contractureIndirect synergist ------------- contractureContralateral antagonist --- underaction

False projection (Hess screen)

OD LR Palsy

Clinical features of nerve palsies

• 6th nerve palsy:- Ocular deviation- Binocular diplopia- Limitation of ocular movement- Abnormal head posture

• 4th nerve palsy:- Ocular deviation- Binocular diplopia- Limitation of ocular movement- Abnormal head posture

• 3rd nerve palsy:- Ocular deviation- Binocular diplopia- Limitation of ocular movement- Abnormal head posture

Pupil

• Treatment:

- Treat the cause- Temporary treatment: occlusion, prisms- Surgical treatment: weakening ----------------> recession

strengthening -----------> resection

1. You have a patient with diplopia. His left eye is turned down and out and his lid is ptotic on that side. What nerve do you suspect and what should you check next?

• This sounds like a CN3 palsy, and you should check his pupillary reflex. Pupillary involvement means the lesion is from a compressive source such as an aneurysm.

Questions

2. This 32 year old overweight woman complains of several months of headaches, nausea, and now double vision. What cranial nerve lesion do you see in this drawing. What other findings might you expect on fundus exam and what other tests might you get?

• This looks like an abducens palsy … actually a bilateral 6th nerve palsy as the patient can’t get either eye to move laterally. While the majority of abducens palsies occur secondary to ischemic events from diabetes, this seems unlikely in a young patient. Her symptoms sound suspicious for pseudotumor (obese, headaches). You should like for papilledema of the optic nerve, get imaging, and possibly send her to neurology for a lumbar puncture with opening pressure.

3. A patient is sent to your neurology clinic with a complaint of double vision. Other than trace cataract changes, the exam seems remarkable normal with good extraocular muscle movement. On covering the left eye with your hand, the doubling remains in the right eye. What do you think is causing this case of diplopia?

• The first question you must answer with a case of diplopia is whether it’s monocular or binocular. This patient has a monocular diplopia. After grumbing to yourself about this patient being inappropriately referred to your neurologic clinic, you should look for refractive problems in the tear film, cornea, lens, etc..

12. A young man complains of complete vision loss (no light perception) in one eye, however, he has no pupil defect. Is this possible? How might you check whether this patient is “faking it?”

• Assuming the rest of the eye exam is normal (i.e. the eye isn’t filled with blood or other media opacity) this patient should have an afferent pupil defect if he can’t see light. There are many tests to check for malingering: you can try eliciting a reflexive blink by moving your fingers near the eye. One of my favorite techniques is to hold a mirror in front of the eye. A seeing eye will fixate on an object in the mirror. Gentle movement of the mirror will result in a synchronous ocular movement as the eye unconsciously tracks the object in the mirror.

Concomitant squint• Definition “angle of deviation”

• Types:- Acc to direction of deviation: esotropia exotropia

hypertropia hypotropia- Acc to laterality of deviation: unilateral alternating

• Clinical picture - ocular deviation

- defective vision

- diplopia???

Concomitant EsotropiasNon Accommodative Accommodative

1) Essential: 6 mo, >15ᵒ, ref +2D, DVD,IO overaction Cross fixation

2) Sensory (Amblyopia)3) Convergence excess4) Divergence insuffeciency5) Basic6) Microtropia7) Acute

Refractive (normal AC/A ratio)

- Full- Partial

Non-refractive(abnormal AC/A

ratio)-Convergence excess-Accommodation weakness

• IO overaction

• DVD

AC/A Ratio

Refractive Accommodative Esotropia

Refractive Partially Accommodative Esotropia

Convergence excess esotropia

Concomitant Exotropias• Early onset: at birth, normal refraction, large angle,

associated neurological manifestations, surgical ttt

• Intermittent: around 2 years, decompesated exophoria

• Sensory: older children & adults

• Consecutive: following surgical correction of ET

Management of strabismus• History: age of onset, duration, glasses

• Exam ocular media: cornea, lens, …

• Fundus exam & refraction (cycloplegic)

• VA: Amblyopia

• Motility in 9 directions of gaze

Alternate Cover test

Exotropia, intermittent

May be visible with or without alternate cover

May have intermittent diplopia, especially when tired or sick

Mom sees misalignment every now and then.

Cover test

Alternate Cover test

Exotropia, Constant

May be visible with or without alternate cover

May or may not have constant diplopia

• Measurement of angle of deviation:- Corneal reflex: pupillary magin -----15ᵒ

midway ----------------30ᵒ

limbus -----------------45ᵒ

- Prism: 1ᵒ = 2 ∆

- Synoptophore

Alternate Cover test with Prism

Exotropia, Constant

Use prism to quantitate the deviation.

Change prism power until movement is neutralized.

20

Prism cover test

• Worth 4 dot test (Binocular vision)

Treatment• Aims:1) Restore binocular vision

2) Improve VA

3) Restore normal appearance

• Lines:1) Cycloplegic refraction & error correction

2) Treat amblyopia: occlusion – penalization

3) Treat eccentric fixation (Pleoptics)

4) Orthoptics

5) Surgery

Nystagmus• Definition

• Types

Pendular Jerky

Vestibular Central Ocular

Physiological Pathological

Clinical Approach to squint

History

1) Age of onset: - Documentation - Significance

2) Direction of deviation: Eso, Exo, Hyper, Hypo

3) Which eye: Alternate? Always the same eye?

4) Mode of onset: sudden? Gradual? Ppt factors

5) Type of deviation: Constant? Intermittent?

Family photos

Amblyopia

H/O trauma, fever, neurologic disorder

Intermittent fusion present good prognosis

Essential ET (6mo) – Accommodative ET (3yrs)

6) Prior treatment: Glasses? Occlusion? Prisms? E.D? Surgery?

7) Medical History: Birth weight, Incubation, Neurological

ROPMysthenia

Clinical Approach to squintFamily photos

Amblyopia

H/O trauma, fever, neurologic disorder

Intermittent fusion present good prognosis

Intermittent exotropia, corneal or conj disease

ROPMysthenia

Inspection of the patient

1) Lid fissure:- Ptosis

III nerve palsy - mysthenia

- Exophthalmos - Enophthalmos

Graves’ blow out fracture

- Hypertelorism - Epicanthal folds

Pseudo Exotropia Pseudo Esotropia

2) Head posture

Face turn Head tilt Chin up/down

Right VI palsy

3) Fixation preference:Alternating Unilateral

Amblyopia

Alternate Cover test

Exotropia, Constant

4) Constancy of deviation:

Constant Variable

- Incomitant- Uncorrected refractive errorHering law

5) Nystagmus

Essential ET

Oscillopsia

III nerve palsy - mysthenia

Graves’ – blow out fracture

III nerve palsy

Pseudo strabismus

Amblyopia

- Incomitant- Uncorrected ref error

Assessment of vision in non verbal children

Fixation and following Preferential looking Catford drum

VEP

Visual Acuity

StereopsisBinocular Vision

Titmus Fly test

• Duction movement

Ductions & Versions

• Binocular movement

• Diagnostic positions of gaze

Cover – Uncover test

Orthophoria, normal

No complaints, asymptomatic

Cover test

Cover – Uncover test

Esophoria, abnormal, common

Only seen when eye is covered

Often asymptomatic, no complaints

Note OS does not move.

Cover – Uncover test

Exophoria, abnormal, common

Only seen when eye is covered

Note OS does not move

Often asymptomatic, no complaints.

Alternate Cover test

Exotropia, intermittent

May be visible with or without alternate cover

May have intermittent diplopia, especially when tired or sick

Mom sees misalignment every now and then.

Cover test

Alternate Cover test

Exotropia, Constant

May be visible with or without alternate cover

May or may not have constant diplopia

Alternate Cover test with Prism

Exotropia, Constant

Use prism to quantitate the deviation.

Change prism power until movement is neutralized.

20

Prism cover test

• A mother brings in her 5-month-old boy because his eyes have been tearing for a couple of months. On further questioning, she reports no discharge or redness, but he squints and turns away from bright lights. He has no significant past ocular or medical history. 

 1   What is the differential diagnosis?

  2   What exam findings would you look for?

Questions

• You are asked to see a 3-year-old girl with an eye turn. Apparently the child's eyes have turned inward since she was a baby, but now the mother notices that the left eye also goes up.  

1   What is the differential diagnosis?

 2   What exam findings would enable you to determine the correct diagnosis?

Additional information: her best-corrected visual acuity is 6/6 OU with +1.00 D OD and +1.50 D OS. The AC/A ratio is normal. The ET is comitant and measures 35 prism diopters at distance and near. She does cross fixate, and there is inferior oblique overaction. There is also no dissociated vertical deviation (DVD) or latent nystagmus present. Worth 4 dot testing demonstrates suppression OS

 3   What type of esotropia does this girl have?

Thank you