title: A comparison of global indices between the Medmont Automated Perimeter and the Humphrey Field Analyzer.
abstract: BACKGROUND
  Two commonly used perimeters in Australia are the Humphrey Field Analyzer II (HFA) and the Medmont Automated Perimeter (MAP). Each device describes the visual field in terms of numerical values called global indices; however, these values are not interchangeable between devices. This study was designed to directly compare the global indices of HFA and MAP visual fields.
  
  
  METHODS
  63 subjects who had suspected glaucoma, ocular hypertension or glaucoma, or were normal controls were recruited selectively. Each patient was tested with the MAP and HFA. Global indices were then compared between tests. These included mean deviation (MD) and pattern standard deviation (PSD) from the HFA and average defect (AD) and pattern defect (PD) from the MAP.
  
  
  RESULTS
  The MD and PSD results were strongly correlated with the AD and PD results, respectively. The relationship between them could be described in terms of two polynomial equations: AD = 0.94+1.31(MD)+0.02(MD)(2) and PD = 2.21(PSD)-0.05(PSD)(2)-0.006. These non-linear relationships may be the result of differences in testing method (test stimulus spectrum, number of testing locations or background luminance) or differences in the way each global index was calculated.
  
  
  CONCLUSIONS
  The AD and PD results obtained from the MAP may be substituted for the MD and PSD results from the HFA after appropriate conversion.
authors: Eye Associates, Park House, Sydney, Australia. john.landers@bigpond.com
authors: John
authors: J
authors: Landers
authors: Alok
authors: A
authors: Sharma
authors: Ivan
authors: I
authors: Goldberg
authors: Stuart
authors: S
authors: Graham
mesh_terms: D005260:Female; D005901:Glaucoma / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000503:physiopathology; D058609:Visual Field Tests / Q000295:instrumentation* / Q000379:methods; D014794:Visual Fields / Q000502:physiology