title: Methodological variations in estimating apparent progressive visual field loss in clinical trials of glaucoma treatment.
abstract: OBJECTIVE
  To compare methods to estimate the incidence of visual field progression used by 3 large randomized trials of glaucoma treatment by applying these methods to a common data set of annually obtained visual field measurements of patients with glaucoma followed up for an average of 6 years.
  
  
  METHODS
  The methods used by the Advanced Glaucoma Intervention Study (AGIS), the Collaborative Initial Glaucoma Treatment Study (CIGTS), and the Early Manifest Glaucoma Treatment study (EMGT) were applied to 67 eyes of 56 patients with glaucoma enrolled in a 10-year natural history study of glaucoma using Program 30-2 of the Humphrey Field Analyzer (Humphrey Instruments, San Leandro, Calif). The incidence of apparent visual field progression was estimated for each method. Extent of agreement between the methods was calculated, and time to apparent progression was compared.
  
  
  RESULTS
  The proportion of patients progressing was 11%, 22%, and 23% with AGIS, CIGTS, and EMGT methods, respectively. Clinical assessment identified 23% of patients who progressed, but only half of these were also identified by CIGTS or EMGT methods. The CIGTS and the EMGT had comparable incidence rates, but only half of those identified by 1 method were also identified by the other.
  
  
  CONCLUSIONS
  The EMGT and CIGTS methods produced rates of apparent progression that were twice those of the AGIS method. Although EMGT, CIGTS, and clinical assessment rates were comparable, they did not identify the same patients as having had field progression.
authors.affiliation: Department of International Health, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205-2103, USA.
authors.forename: J
authors.initials: J
authors.lastname: Katz
authors.forename: N
authors.initials: N
authors.lastname: Congdon
authors.forename: D S
authors.initials: DS
authors.lastname: Friedman
mesh_terms: D018450:Disease Progression; D004358:Drug Therapy; D018463:Filtering Surgery; D005500:Follow-Up Studies; D005902:Glaucoma, Open-Angle / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D015994:Incidence; D053685:Laser Therapy; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D014786:Vision Disorders / Q000175:diagnosis* / Q000503:physiopathology; D058609:Visual Field Tests / Q000379:methods* / Q000592:standards; D014794:Visual Fields