Exam

Cover Test

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Cover Test, Cover-Uncover Test, Alternate Eye Cover Test

  • See Also
  1. Pediatric Eye Exam
  2. Strabismus
  • Indications
  1. Testing for Strabismus (Exotropia or Esotropia)
  1. Test with both a near object and a far object
  2. Repeat each test 3 times for reproducibility
  3. Choose an interesting object for a child to fixate on (e.g. small toy, penlight)
  • Technique
  • Cover Test
  1. Child fixates on a point (e.g. small toy, penlight)
  2. Cover one eye
  3. Observe for movement of uncovered eye
    1. Abnormal or positive test suggests manifest strabsimus (tropia)
  4. Cover other eye and repeat test
  • Technique
  • Cover-Uncover Test
  1. Child fixates on a point (e.g. small toy, penlight)
  2. Cover one eye for 1-2 seconds
  3. Rapidly uncover the eye
  4. Observe for movement of previously covered eye from a deviated position back to fixation on object
    1. Abnormal or positive test suggests latent Strabismus (phoria)
  5. Cover other eye and repeat test
  • Technique
  • Alternate Cover Test
  1. Child fixates on a point (e.g. small toy, penlight)
  2. Cover one eye for 1-2 seconds
  3. Rapidly uncover the first eye and cover the second for 1-2 seconds
  4. Rapidly uncover the second eye and cover the first again for 1-2 seconds
  5. Observe for refixation (suggests hidden phoria)
  • Interpretation (based on movement of uncovered eye)
  1. Normal: uncovered eye maintains current position
  2. Exotropia: Eye moves inward to pick up fixation
  3. Esotropia: Eye moves outward to pick up fixation
  • Interpretation
  • False Results
  1. Causes of False Positive Cover Test
    1. Inattention of child
  2. Causes of False Negative Cover Test
    1. Amblyopia of uncovered eye prevents re-fixation
  • References
  1. Berson (1987) Ophthalmology Study Guide, AAO, p. 104
  2. Essman (1992) Am Fam Physician 46(4):1243-52 [PubMed]
  3. Mills (1999) Am Fam Physician 60(3):907-16 [PubMed]
  4. Simon (2001) Am Fam Physician 64(4):623-8 [PubMed]