title: Visual field progression in glaucoma: estimating the overall significance of deterioration with permutation analyses of pointwise linear regression (PoPLR).
abstract: OBJECTIVE
  To establish a method for estimating the overall statistical significance of visual field deterioration from an individual patient's data, and to compare its performance to pointwise linear regression.
  
  
  METHODS
  The Truncated Product Method was used to calculate a statistic S that combines evidence of deterioration from individual test locations in the visual field. The overall statistical significance (P value) of visual field deterioration was inferred by comparing S with its permutation distribution, derived from repeated reordering of the visual field series. Permutation of pointwise linear regression (PoPLR) and pointwise linear regression were evaluated in data from patients with glaucoma (944 eyes, median mean deviation -2.9 dB, interquartile range: -6.3, -1.2 dB) followed for more than 4 years (median 10 examinations over 8 years). False-positive rates were estimated from randomly reordered series of this dataset, and hit rates (proportion of eyes with significant deterioration) were estimated from the original series.
  
  
  RESULTS
  The false-positive rates of PoPLR were indistinguishable from the corresponding nominal significance levels and were independent of baseline visual field damage and length of follow-up. At P < 0.05, the hit rates of PoPLR were 12, 29, and 42%, at the fifth, eighth, and final examinations, respectively, and at matching specificities they were consistently higher than those of pointwise linear regression.
  
  
  CONCLUSIONS
  In contrast to population-based progression analyses, PoPLR provides a continuous estimate of statistical significance for visual field deterioration individualized to a particular patient's data. This allows close control over specificity, essential for monitoring patients in clinical practice and in clinical trials.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Neil
authors.initials: N
authors.lastname: O'Leary
authors.forename: Balwantray C
authors.initials: BC
authors.lastname: Chauhan
authors.forename: Paul H
authors.initials: PH
authors.lastname: Artes
mesh_terms: D000368:Aged; D000465:Algorithms; D018450:Disease Progression; D005189:False Positive Reactions; D005901:Glaucoma / Q000503:physiopathology*; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D015233:Models, Statistical; D011237:Predictive Value of Tests; D014786:Vision Disorders / Q000503:physiopathology*; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*