title: Comparison of visual acuity measured with Allen figures and Snellen letters using the B-VAT II monitor.
abstract: OBJECTIVE
  Allen figure optotypes commonly are used to measure visual acuity in young children. Children with normal acuity measured with Allen figures sometimes are found to have unsuspected amblyopia that is detected when they are tested with Snellen letters. The correlation between visual acuities measured with these two optotype charts has not been well studied. The authors compared visual acuities measured with Allen figure and Snellen letter optotypes using the Mentor B-VAT II monitor.
  
  
  METHODS
  The study design was a nonrandomized, comparative clinical trial.
  
  
  METHODS
  The study was composed of 12 adult subjects.
  
  
  METHODS
  Visual acuities were measured using both Allen figure and Snellen letter optotypes using the B-VAT II monitor. The images were progressively blurred using plus lenses.
  
  
  METHODS
  Visual acuity was measured.
  
  
  RESULTS
  At visual acuity levels of 20/60 or better, Allen figure testing averaged 1.5 lines better than Snellen letter testing; between 20/70 and 20/200 visual acuities, the difference was 2.5 lines.
  
  
  CONCLUSIONS
  Allen figure testing with the B-VAT II monitor overestimates visual acuity compared with testing with Snellen letters. This appears to result primarily from the construction of the optotypes. This discrepancy should be considered when visual acuity is measured in young children.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University Medical Center, St. Louis, Missouri 63110, USA.
authors.forename: G T
authors.initials: GT
authors.lastname: Lueder
authors.forename: D
authors.initials: D
authors.lastname: Garibaldi
mesh_terms: D000328:Adult; D006801:Humans; D012030:Refractive Errors / Q000503:physiopathology; D014787:Vision Tests / Q000295:instrumentation* / Q000379:methods; D014792:Visual Acuity / Q000502:physiology*