Strabismus
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Strabismus is a misalignment of the eyes due to an imbalance in extraocular muscle function, leading to impaired binocular vision and potential amblyopia in children.
Aetiology
- Congenital strabismus: present at birth or within the first six months.
- Acquired strabismus: secondary to neurological conditions, trauma, or refractive errors.
- Refractive strabismus: due to uncorrected hypermetropia leading to accommodative esotropia.
- Paralytic strabismus: caused by cranial nerve palsies affecting extraocular muscles.
Pathophysiology
- Disruption in coordination between extraocular muscles results in misalignment of visual axes.
- Brain suppression of the deviated eye’s image can lead to amblyopia in children.
- Long-standing strabismus in adults may cause diplopia.
Risk Factors
- Family history of strabismus.
- Prematurity and low birth weight.
- Neurological conditions (e.g., cerebral palsy, hydrocephalus).
- Refractive errors (especially hypermetropia).
- Cranial nerve palsies.
Signs and Symptoms
- Eye misalignment: esotropia (inward), exotropia (outward), hypertropia (upward), hypotropia (downward).
- Diplopia: common in acquired strabismus.
- Head tilting: compensatory posture to minimise diplopia.
- Reduced stereopsis: impaired depth perception.
Investigations
- Cover-uncover test: assesses for manifest strabismus.
- Alternate cover test: detects latent strabismus (phoria).
- Ocular motility assessment: evaluates extraocular muscle function.
- Refraction testing: determines the role of refractive errors.
- Neurological assessment: indicated if cranial nerve palsy is suspected.
Management
1. Non-Surgical Management:
- Refractive correction: glasses for accommodative esotropia.
- Occlusion therapy: patching of the dominant eye to prevent amblyopia.
- Prism lenses: for mild strabismus and diplopia correction.
- Botulinum toxin injections: temporary treatment for certain types of strabismus.
2. Surgical Management:
- Strabismus surgery: realignment of extraocular muscles to improve ocular positioning.
- Adjustable suture techniques: used in adults to refine alignment postoperatively.
3. Referral:
- Ophthalmology: all suspected cases require assessment, patient should be referred.
- Orthoptics: for non surgical management and vision therapy.
- Neurology: if an underlying neurological cause is suspected.