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Amblyopia

Table of Contents

  • Introduction
  • Aetiology
  • Classification
  • Clinical Features
  • Investigations
  • Management
  • Complications
  • References
  • Related Notes
  • Test Yourself

Introduction

  • Amblyopia (lazy eye) is unilateral or bilateral reduction in visual acuity due to insult to the visual pathways during the critical period of visual development.
  • Critical period: birth to 3 months, some development until 7-8 years.
  • It is a common cause of preventable visual disability, affecting about 2-5% of the population.
  • Early detection and treatment can prevent or reverse most amblyopic visual loss.

Aetiology

  • Caused by ocular pathology interfering with cortical visual development:
  • Squint (strabismus)
  • High refractive error (anisometropia/isometropia)
  • Visual deprivation (e.g., congenital cataracts, ptosis)

Classification

  • Strabismic amblyopia: most common; occurs in eye with ocular misalignment.
  • Anisometropic amblyopia: unequal refractive error causing blurred image in one eye.
  • Isometropic amblyopia: bilateral reduced acuity from large, equal refractive errors in both eyes.
  • Deprivation amblyopia: caused by media opacities; least common but most damaging.

Clinical Features

History

  • Often asymptomatic; detected on vision screening.
  • History of prematurity (higher risk of squint).
  • Family history of amblyopia, squint, or glasses.

Examination

  • Age-appropriate vision testing.
  • Record spectacle power.
  • Stereopsis and binocular function testing.
  • External eye exam (ptosis, haemangiomas).
  • Anterior segment exam (media opacity).
  • Ocular motility and alignment.
  • Fundoscopy.
  • Cycloplegic refraction.

Investigations

  • Usually clinical diagnosis from history and examination.
  • Neuroimaging if vision loss unexplained or deteriorating despite treatment.

Management

  • Remove obstacles to vision (e.g., cataracts).
  • Correct refractive errors fully (cycloplegic refraction).
  • Patching: full-time patching of good eye to force use of amblyopic eye; duration depends on severity:
  • Severe amblyopia (20/100 to 20/400): ~6 hours/day
  • Moderate (20/40 to 20/80): start 2 hours/day, increase to 6 hours if needed.
  • Monitor for occlusion amblyopia in patched eye; ensure compliance via education and support.
  • Atropine penalisation: cycloplegic drops in good eye for children non-compliant with patching; daily or weekend-only dosing effective.

Complications

  • Untreated amblyopia → permanent reduced visual acuity.
  • Poor compliance with patching common.
  • Atropine drops can cause side effects such as photophobia.

References

  • Wallace D, Repka M, Lee K, Melia M, Christiansen S, Morse C et al. Amblyopia Preferred Practice Pattern®. Ophthalmology. 2018;125(1):P105-P142.
  • Randomized trials on patching and atropine regimens (2003-2004).
  • Acute Angle-Closure Glaucoma
  • Age-related Macular Degeneration (ARMD)
  • Ametropia
  • Anisocoria
  • Anterior Uveitis (Iritis)

Test Yourself

  • [Link to clinical questions on amblyopia and eye examination]

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