title: Distance doubling visual acuity test: a reliable test for nonorganic visual loss.
abstract: BACKGROUND
  To determine the value of the distance doubling visual acuity test in the diagnosis of nonorganic visual loss in a comparative observational case series.
  
  
  METHODS
  Twenty-one consecutive patients with nonorganic visual acuity loss and 21 subjects with organic visual loss as controls were included. Best corrected visual acuity was tested at the normal distance of 5 meters using Landolt Cs. The patient was then repositioned and best corrected visual acuity was tested with the previous optotypes at double the distance via a mirror.
  
  
  RESULTS
  Nonorganic visual acuity loss was identified in 21 of 21 patients. Sensitivity and specificity of distance-doubling visual acuity test in functional visual loss were found to be 100% (CI; 83%-100%) and 100% (CI; 82%-100%), respectively.
  
  
  CONCLUSIONS
  Distance doubling visual acuity test is widely used to detect nonorganic visual loss. Our results show that this test has a high specificity and sensitivity to detect nonorganic visual impairment.
authors.affiliation: Department of Neuro-Ophthalmology and Strabismology, Kantonsspital, St. Gallen, Switzerland.
authors.forename: Sebastian Martin
authors.initials: SM
authors.lastname: Zinkernagel
authors.forename: Daniel Stephane
authors.initials: DS
authors.lastname: Mojon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D006801:Humans; D008306:Malingering / Q000175:diagnosis; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014786:Vision Disorders / Q000175:diagnosis*; D014787:Vision Tests; D014792:Visual Acuity; D055815:Young Adult