title: Reliability and consistency of visual acuity and contrast sensitivity measures in advanced eye disease.
abstract: OBJECTIVE
  The purpose of this article is to establish reliability of standard visual function measures in patients with severe vision loss.
  
  
  METHODS
  Legally blind subjects were enrolled in a repeated-measures study to determine the reproducibility of a battery of psychophysical vision measures. Tests reported here include ETDRS visual acuity (VA) under regular and dim illumination and Pelli-Robson letter contrast sensitivity (CS) under regular, dim, and glare conditions. Two to five test repetitions were performed at monthly intervals. Subject groups included retinitis pigmentosa (RP) (n = 29), macular disease (MD) (n = 17), optic nerve disease (ON) (n = 4), diabetic retinopathy (DR) (n = 5), and other retinal diseases (OR) (n = 10).
  
  
  RESULTS
  For most subject groups, VA measures had mean 95% coefficient of repeatability (CR.95) of 0.20 (group means between 0.13 and 0.36) log units, and CS measures had mean CR.95 of 0.35 (group means between 0.19 and 0.48) log units.
  
  
  CONCLUSIONS
  The established reliability of VA and CS tests in subjects with severe visual impairments will allow investigators to determine whether a significant change in vision has occurred during future clinical trials to reverse, halt, or slow vision loss. The criterion for change needs to be larger than for normally sighted controls, i.e., approximately two to three lines for VA and between eight to 11 letters for CS.
authors.affiliation: Lions Vision Center, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Ava K
authors.initials: AK
authors.lastname: Kiser
authors.forename: Derek
authors.initials: D
authors.lastname: Mladenovich
authors.forename: Fariba
authors.initials: F
authors.lastname: Eshraghi
authors.forename: Debra
authors.initials: D
authors.lastname: Bourdeau
authors.forename: Gislin
authors.initials: G
authors.lastname: Dagnelie
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015350:Contrast Sensitivity / Q000502:physiology*; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D010775:Photic Stimulation; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014787:Vision Tests / Q000379:methods; D015354:Vision, Low / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology*