Strabismus

1. Epidemiology
   1. Accounts for 50% of Amblyopia (most common cause)
2. Types
   1. Esodeviation (Cross-Eyed)
      1. Both eyes turn inward
      2. Accounts for >50% of ocular deviations in children
   2. Exodeviation (walleye)
      1. One eye turns outward while other eye faces forward
      2. Deviation most evident with distant vision
      3. Parents often note changes on a bright day
         1. Eye deviates outward
         2. Child closes one eye
   3. Fourth Cranial Nerve palsy (superior oblique palsy)
      1. Eye rises when Head Tilted to side of palsy
      2. Findings
         1. Hypertropia (deviating eye turns up)
         2. Hypotropia (deviating eye turns down)
3. Signs: Screen at every well child check
   1. Test Specifically for Strabismus
      1. Only 50% children with Strabismus have obvious defect
4. Signs: Organized by Strabismus type
   1. Manifest (Tropia): Strabismus that is always present
      1. Corneal Light Reflex
      2. Cover-Uncover Exam
      3. Bruckner Test (Red Reflex)
      4. Fixation and following
   2. Intermittent Strabismus
      1. Healthy newborns develop alignment after age 4 weeks
      2. Intermittent exodeviation under 6 months
      3. Esodeviation much more likely to be pathologic
   3. Latent (Phoria): Present if binocular vision blocked
      1. Only found when specifically tested
      2. Cover-Uncover Exam
5. Signs: Small-Angle Strabismus (Accommodative esotropia)
   1. Identified with Cover Testing
   2. Seen in Farsighted toddlers
   3. Corrected with glasses or bifocals
   4. Abnormal use of accommodative convergence
      1. Normal reflex for near vision
      2. Farsighted children use convergence all the time
6. Screening
   1. General
      1. See testing above
      2. Photoscreening (picture of eyes and Red Reflex)
         1. May be used in future for mass screening
   2. Timing
      1. Screen frequently in first 3 years of life
      2. Example protocol: 8, 12, 18, 25, 31, 37 months of age
      3. Early diagnosis results in best outcome
   3. References
      1. Williams (2002) BMJ 324: 1549-51
7. Diagnosis: Immediate Ophthalmology Consult Indications
   1. Manifest (constant) deviation in any age
   2. Intermittent Exodeviation >6 months
   3. Intermittent Esodeviation >2 months
8. Diagnosis: Pitfalls - Pseudostrabismus
   1. Esotropia may be apparent despite normal alignment
   2. Iris appears to be surrounded by different white
   3. Illusion of different amount white on each side of iris
      1. Flat nasal bridge
      2. Large epicanthal folds
   4. Differentiate from Strabismus with proper testing
      1. See Strabismus signs above
   5. Refer to Ophthalmology for any question of misalignment
9. Management: Early consultation is critical
   1. Surgical Realignment of eyes
   2. Amblyopia treated prior to realignment surgery
10. Prognosis for congenital esotropia
    1. Repair under age 1 year
       1. Offers best chance of near-normal binocular vision
    2. Repair over age 1 year
       1. Significantly worse prognosis for binocular vision
11. References
    1. Berson (1987) Ophthalmology Study Guide, AAO, p. 95-110
    2. Essman (1992) Am Fam Physician 46(4):1243-52
    3. Mills (1999) Am Fam Physician 60(3):907-16
    4. Simon (2001) Am Fam Physician 64(4):623-8