Strabismus

Introduction

Strabismus is misalignment usually of one eye preventing simultaneous viewing of an object by both eyes.

Onset in children under 7 years interferes with the development of the visual system of the deviating eye in the brain leading to amblyopia.

Acute onset at an older age causes double vision.

Diplopia does not occur in children because of the ability to suppress the second image or development of amblyopia.

Amblyopia does not occur if the deviation alternated from one eye to the other.
The more frequent types are horizontal misalignment.

Esotropia is convergent deviation and exotropia is divergent deviation.

Causes of strabismus

Its causes include the following:

1. Congenital misalignment
2. Acquired deviation
3. Paralysis of the cranial nerve VI, III or IV
4. Fibrosis in an extraocular muscle
5. Myasthenia gravis
6. Intraocular lesion e.g. retinoblastoma and macular scar

Symptoms of strabismus

1. Misalignment of the eye
2. Impaired judgement of depth or distance
3. Diplopia or double vision

Signs of strabismus

1. Deviation of the corneal light reflex in one eye from a central position
2. Movement of the deviating eye to take up fixation when the fixing eye is covered
3. Normal extraocular eye movement (in non-paralytic strabismus)
4. Limitation of eye movement (in paralytic or restrictive strabismus)
5. Hypermetropia on refraction in children
6. Retinal lesion e.g. retinoblastoma

Investigations

• Cycloplegic refraction in children
• Other specific tests for suspected causes e.g. myasthenia gravis or retinoblastoma

Treatment for strabismus

Objectives

The treatment objectives of strabismus include the following:

1. To identify and correct any significant refractive error
2. To treat any amblyopia
3. To relieve any diplopia
4. To correct the misalignment
5. To treat any underlying condition

Non-pharmacological treatment

1. Spectacle correction of any refractive error
2. Treatment of amblyopia in the deviating eye by patching the non deviating eye
3. Use of prisms to correct small deviations
4. Patching of the deviating eye to relieve diplopia in older patients

Pharmacological treatment

Nil

Referral Criteria

All patients diagnosed with strabismus must be referred to the eye specialist for further management.