Amblyopia

1. Definition
   1. Poor vision not correctable with eyeglasses
   2. No known primary cause (normal Cornea, lens, Retina)
2. Epidemiology
   1. Prevalence: 2-4% of US Children
   2. Occurs in children up to age 6 years
3. Etiologies
   1. Strabismus (most common cause of Amblyopia)
      1. Misalignment of eyes
   2. Refractive Amblyopia
      1. Anisometropia
         1. Large difference in Refractive Error between eyes
         2. Causes
            1. Bilateral Hyperopia (most common)
            2. Severe unilateral Hyperopia or Myopia
            3. Astigmatism
      2. Isometric Amblyopia
         1. Severe, equal Refractive Errors
   3. Deprivation Amblyopia (least common)
      1. Congenital Cataract
      2. Retinoblastoma
      3. Corneal scarring
      4. Vitreous opacity
      5. Severe Ptosis
      6. Optic atrophy
      7. Iatrogenic excessive patching
4. Pathophysiology
   1. Occurs in developmentally immature eye
      1. During first 6 months of life
      2. Acuity normally improves rapidly 20/400 => 20/80
      3. Eye fully matures by age 9 years
   2. Normal maturity
      1. Requires clear, equal, aligned image for each eye
      2. Conflicting data with
         1. Strabismus (2 competing images)
         2. Anisometropia (1 clear, 1 blurred image)
      3. Brain suppresses information from the "bad" eye
      4. Continued suppression leads to permanent Vision Loss
         1. Adults unable to suppress different images
         2. Adults experience Diplopia
5. Screening
   1. See Pediatric Vision Screening
   2. Exam for associated ocular disease
   3. Test for Strabismus
      1. Corneal Light Reflex
      2. Cover-Uncover Exam
      3. Bruckner Test (Red Reflex)
      4. Fixation and following
   4. Differentiate Refractive Error from Amblyopia
      1. Pinhole Test
6. Management
   1. Treat underlying cause early
      1. Address Cataracts and Refractive Error if present
      2. Correct Strabismus if present
   2. Encourage writing or drawing while good eye obscured
   3. Force child to use amblyopic eye by obscuring good eye
      1. Patch "good", dominant eye (usual course)
      2. Opaque contact lenses
      3. Cloth over glasses on good eye side
      4. Prescrition glasses to blur good eye
      5. Atropine (0.5-1%) 1 drop for 2-7 days per week
         1. Indicated in noncompliant children
         2. Apply to good eye to dilate pupil
         3. Prevents accomodation and causes vision blurring
7. Prognosis
   1. Early, aggressive, and consistent therapy is critical
   2. Amblyopia recurs in 24% after 1 year
      1. Be vigilant about surveillance
   3. Amblyopia nearly irreversible after age 9 years
      1. New studies suggest teens may benefit from therapy
      2. Scheiman (2005) Arch Ophthalmol 123:437-47
8. Resources: Patient Education
   1. Information from your Family Doctor
      1. http://www.familydoctor.org/handouts/460.html
9. References
   1. Berson (1987) Ophthalmology Study Guide, AAO, p. 95-110
   2. Doshi (2007) Am Fam Physician 75(3):361-8
   3. Essman (1992) Am Fam Physician 46(4):1243-52
   4. Mills (1999) Am Fam Physician 60(3):907-16
   5. Rubin (1993) Pediatr Clin North Am 40:727-35
   6. Simon (2001) Am Fam Physician 64(4):623-8