Visual Acuity

Aka: Visual Acuity, Vision Screening, Snellen Chart, ETDRS Visual Acuity Chart, Rosenbaum Chart, HOTV Card

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II. Precautions

  1. Visual Acuity is THE Vital Sign of the eye
    1. Obtain Visual Acuity on all patients with eye complaints
    2. Obtain before remainder of exam (e.g. flashlight tests, topical agents, Mydriatic use)
    3. In acute eye complaints, perform Visual Acuity with their Vision correction (e.g. glasses)

III. Exam: Distance Vision

  1. Vision with each eye individually and together
  2. Appropriate chart (usually 20 foot distance or 6 meters to chart, or half-length at 10 feet or 3 meters)
    1. Snellen Letters (6 years and older, adults)
    2. Snellen Numbers (Non-english speaking or illiterate)
    3. Tumbling E (Children ages 3 to 5 years)
    4. HOTV Card (Children ages 3 to 5 years)
    5. Picture Tests (Childen ages 3 to 5 years)
  3. Alternative handheld chart (Rosenbaum Chart)
    1. Rosenbaum Chart held 16 inches (or 36 cm) away from patient's eyes
    2. Evaluates near Vision (in contrast to standard chart at 20 feet, which evaluates distance Vision)
  4. Interpretation
    1. Vision is recorded based on the smallest print letters the patient can read with half the answers correct
    2. Vision recorded as 20/X-Y
      1. Where 20 refers to feet from chart
      2. Where X refers to the distance a person with normal Vision can still read the same line
      3. Where Y refers to the number of missed items for the particular line
  5. Myopia suggested if Vision improves with pinhole
    1. Vision testing through a small pinhole corrects for Refractive Errors
    2. Consider pinhole for Vision testing in a patient who did not bring their glasses to evaluation
  6. If Vision less than 20/200, assess best Vision with:
    1. Finger Counting (CF) at 1 foot and at 6 inches
    2. Hand Movements (HM)
    3. Light Perception (LP)
    4. No light Perception (NLP): total blindness

IV. Interpretation: Normal Vision for children 2.5 to 6 years

  1. Month 30-35: 20/60 (or 6/20) or better
  2. Month 36-47: 20/50 (or 6/15) or better
  3. Month 48-59: 20/40 (or 6/12) or better
  4. Month 60-72: 20/30 (or 6/10) or better
  5. Pan (2009) Opto Vis Sci 86(6): 607-12 [PubMed]

V. Management: Indications for referral to eye care specialist

  1. Indications for adults
    1. See Preventive Eye Examination for screening guidelines (e.g. Glaucoma)
    2. Uncorrected Vision <20/50 or
    3. One line difference (on Snellen Chart) between eyes
  2. Indications for children
    1. Any Age: Two line difference between eyes
      1. Example: OD 20/25 and OS 20/40
    2. Age 3-4: Either eye worse than 20/50
    3. Age 4-5: Either eye worse than 10/20 or 20/40
    4. Age >5: Either eye worse than 10/15 or 20/30 (<3 of 5 characters correct)
    5. References
      1. (2003) Pediatrics 111:903 [PubMed]

VI. Exam: Near Vision

  1. Not generally screened
  2. Presbyopia occurs after age 40 years

VII. Exam: Refraction

  1. Performed by Optometry or Ophthalmology
  2. Measures optical error of eyes to prepare lenses

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