title: Towards an optimal perimetric strategy for progression detection in glaucoma: from fixed-space to adaptive inter-test intervals.
abstract: BACKGROUND
  The aim was to compare two perimetric strategies for progression detection in glaucoma.
  
  
  METHODS
  Two perimetric strategies for progression detection were compared by means of a thought experiment in a theoretical cohort. In strategy I, visual field testing is performed with fixed-space inter-test intervals at a frequency of two tests per year. In strategy II, the frequency of visual field testing is set to one test per year as long as the fields are apparently unchanged, whereas as soon as progression is suspected, confirmation or falsification is performed within a short time span. Outcome measures were the time delay between the progression event and the diagnosis of definite progression, and the number of visual field tests performed per patient per year.
  
  
  RESULTS
  Average time delay between the actual progression event and the final diagnosis of definite progression was 15 months in the case of strategy I and 6 months in the case of strategy II. Maximum time delays were 18 and 12 months respectively. The frequency of visual field testing was 2 tests per patient per year for strategy I and 1.45 tests per patient per year for strategy II.
  
  
  CONCLUSIONS
  Perimetry in glaucoma can be optimised by postponing the next test in the case of an apparently stable field and accelerating the next test in the case of a suspected progression. This results in an earlier diagnosis, a lower perimetric frequency and a shorter period of uncertainty for the patient.
authors.affiliation: Department of Ophthalmology, University of Groningen Medical Center, P.O. Box 30.001, 9700 RB, Groningen, The Netherlands. n.m.jansonius@ohk.umcg.nl
authors.forename: Nomdo M
authors.initials: NM
authors.lastname: Jansonius
mesh_terms: D001499:Bayes Theorem; D018450:Disease Progression; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D008962:Models, Theoretical; D011237:Predictive Value of Tests; D013997:Time Factors; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields