title: Factors that influence standard automated perimetry test results in glaucoma: test reliability, technician experience, time of day, and season.
abstract: OBJECTIVE
  To determine the influence of several factors on standard automated perimetry test results in glaucoma.
  
  
  METHODS
  Longitudinal Humphrey field analyzer 30-2 Swedish interactive threshold algorithm data from 160 eyes of 160 glaucoma patients were used. The influence of technician experience, time of day, and season on the mean deviation (MD) was determined by performing linear regression analysis of MD against time on a series of visual fields and subsequently performing a multiple linear regression analysis with the MD residuals as dependent variable and the factors mentioned above as independent variables. Analyses were performed with and without adjustment for the test reliability (fixation losses and false-positive and false-negative answers) and with and without stratification according to disease stage (baseline MD).
  
  
  RESULTS
  Mean follow-up was 9.4 years, with on average 10.8 tests per patient. Technician experience, time of day, and season were associated with the MD. Approximately 0.2 dB lower MD values were found for inexperienced technicians (P < 0.001), tests performed after lunch (P < 0.001), and tests performed in the summer or autumn (P < 0.001). The effects of time of day and season appeared to depend on disease stage. Independent of these effects, the percentage of false-positive answers strongly influenced the MD with a 1 dB increase in MD per 10% increase in false-positive answers.
  
  
  CONCLUSIONS
  Technician experience, time of day, season, and the percentage of false-positive answers have a significant influence on the MD of standard automated perimetry.
authors.affiliation: Department of Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Francisco G
authors.initials: FG
authors.lastname: Junoy Montolio
authors.forename: Christiaan
authors.initials: C
authors.lastname: Wesselink
authors.forename: Marijke
authors.initials: M
authors.lastname: Gordijn
authors.forename: Nomdo M
authors.initials: NM
authors.lastname: Jansonius
mesh_terms: D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis; D009881:Ophthalmic Assistants / Q000193:education*; D015203:Reproducibility of Results; D012621:Seasons; D013997:Time Factors; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests / Q000592:standards*; D014794:Visual Fields