title: The repeatability of mean defect with size III and size V standard automated perimetry.
abstract: OBJECTIVE
  The mean defect (MD) of the visual field is a global statistical index used to monitor overall visual field change over time. Our goal was to investigate the relationship of MD and its variability for two clinically used strategies (Swedish Interactive Threshold Algorithm [SITA] standard size III and full threshold size V) in glaucoma patients and controls.
  
  
  METHODS
  We tested one eye, at random, for 46 glaucoma patients and 28 ocularly healthy subjects with Humphrey program 24-2 SITA standard for size III and full threshold for size V each five times over a 5-week period. The standard deviation of MD was regressed against the MD for the five repeated tests, and quantile regression was used to show the relationship of variability and MD. A Wilcoxon test was used to compare the standard deviations of the two testing methods following quantile regression.
  
  
  RESULTS
  Both types of regression analysis showed increasing variability with increasing visual field damage. Quantile regression showed modestly smaller MD confidence limits. There was a 15% decrease in SD with size V in glaucoma patients (P = 0.10) and a 12% decrease in ocularly healthy subjects (P = 0.08).
  
  
  CONCLUSIONS
  The repeatability of size V MD appears to be slightly better than size III SITA testing. When using MD to determine visual field progression, a change of 1.5 to 4 decibels (dB) is needed to be outside the normal 95% confidence limits, depending on the size of the stimulus and the amount of visual field damage.
authors: Department of Ophthalmology, University of Iowa,College of Medicine, 200 Hawkins Drive, Iowa City, IA 52242-1053, USA. michael-wall@uiowa.edu
authors: Michael
authors: M
authors: Wall
authors: Carrie K
authors: CK
authors: Doyle
authors: K D
authors: KD
authors: Zamba
authors: Paul
authors: P
authors: Artes
authors: Chris A
authors: CA
authors: Johnson
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D005901:Glaucoma / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012607:Scotoma / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D012684:Sensory Thresholds; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields / Q000502:physiology*