Amblyopia

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General

  • Visual development completed between the ages of 10 and 16
  • Critical period (during which amblyopia can be reversed)
    • up to 7-8 years in strabismus
    • may be longer in anisometropia (up to adolescence)

Causes

  • Strabismus
  • Anisometropia
  • Stimulus deprivation (e.g., cataract, ptosis)
  • Bilateral ametropia (usually due to high hyperopia)
  • Astigmatism (usually > 1 diopter)

Diagnosis

  • If there is no organic lesion, a difference of at least two visual acuity levels between the best-corrected vision of both eyes indicates amblyopia
  • Single optotype acuity is often better than optotype line acuity (due to the “crowding” phenomenon)

Examination for early detection

  • Immediately in case of eye abnormalities
  • At the age of 6 months if there is no fixation, strabismus, developmental delay, premature birth (in the first 3 months intermittent strabismus is part of the normal development)
  • Recommended for all children at age 2-3 (rule out refractive errors, microstrabismus…)
  • Test line acuity! May only be detected this way, e.g., in strabismus, as single optotypes do not cause “crowding” phenomenon

Approach in Adults

  • 1. History of poor vision in one eye since childhood?
  • 2. Is there a cause for amblyopia?
    • Strabismus: History of strabismus surgery? Amblyopia treatment with patching?
    • Deprivation: Cataract in childhood? Ptosis? Corneal opacity?
    • Anisometropia: Different refractive errors?
    • Ametropia: Uncorrected high refractive error? High astigmatism?
  • 3. Stable? Amblyopia does not progress in adulthood!
  • 4. Visual acuity? If worse than counting fingers -> no amblyopia!
  • 5. Optic atrophy/optic disc swelling, visual field defect, RAPD? If yes -> No amblyopia!
    • Cave: Minimal relative afferent pupillary defect (RAPD) possible, but a prominent RAPD is not typical for amblyopia

Treatment

  • Occlusion of the normal eye
  • Penalization: Application of atropine -> blurred vision in the better eye (only if compliance is poor)
  • If no improvement occurs after 6 months of treatment, further treatment is likely to be unsuccessful.

Sources

  • EyeWiki Amblyopia
  • Amblyopia by Dr. Andrew G. Lee
  • The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease; Nika Bagheri MD, Brynn Wajda MD, et al; Lippincott Williams&Wilkins; 7th Edition (2016)
  • Kanski’s Clinical Ophthalmology: A Systematic Approach; Jack J. Kanski MD, Brad Bowling MD; Saunders Ltd.; 8th Edition (2015)