title: Validation of point-wise exponential regression to measure the decay rates of glaucomatous visual fields.
abstract: OBJECTIVE
  This study was conducted to validate a recently described technique for measuring the rates of visual field (VF) decay in glaucoma.
  
  
  METHODS
  A pointwise exponential regression (PER) model was used to calculate average rates of faster and slower deteriorating VF components, and that of the entire VF. Rapid progressors had a faster component rate of >25%/year. Mean deviation (MD) and visual field index (VFI) forecasts were calculated by (1) extrapolation of linear regression of MD and VFI, and (2) calculation de novo from the PER-predicted final thresholds.
  
  
  RESULTS
  The mean (± SD) years of follow-up and number of VFs were 9.2 (± 2.7) and 13.7 (± 5.8), respectively. The median rates of the decay were -0.1 and 3.6 (%/year) for the slower and the faster components, respectively. The "rapid progressors" (32% of eyes) had a mean decay rate of 52.2%/year. In comparison with actual values, the average absolute difference and the mean squared error for MD forecasts with linear extrapolation of indices were 3.58 dB and 31.91 dB(2), and with the de novo recalculation from PER predictions were 2.95 dB and 17.49 dB(2), respectively. Similar results were obtained for VFI forecasts. Comparisons of the prediction errors for both the MD and VFI favored the PER forecasts (P < 0.001).
  
  
  CONCLUSIONS
  PER for measuring rates of VF decay is a robust indicator of rates across a wide range of disease severity and can predict future global indices accurately. The identification of "rapid progressors" identifies high-risk patients for appropriate treatment.
authors: Jules Stein Eye Institute, University of California at Los Angeles School of Medicine, Los Angeles, California 90095, USA.
authors: Parham
authors: P
authors: Azarbod
authors: Dennis
authors: D
authors: Mock
authors: Elena
authors: E
authors: Bitrian
authors: Abdelmonem A
authors: AA
authors: Afifi
authors: Fei
authors: F
authors: Yu
authors: Kouros
authors: K
authors: Nouri-Mahdavi
authors: Anne L
authors: AL
authors: Coleman
authors: Joseph
authors: J
authors: Caprioli
mesh_terms: D000368:Aged; D018450:Disease Progression; D005500:Follow-Up Studies; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D008954:Models, Biological; D012044:Regression Analysis; D012720:Severity of Illness Index; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*