title: Using the arteriolar Pressure Attenuation Index to predict ocular hypertension progression to open-angle glaucoma.
abstract: BACKGROUND
  Vascular phenomena are considered important to optic nerve and visual field progression in open-angle glaucoma (OAG). A recently described formulation, the Pressure Attenuation Index (PAI), links arteriolar caliber variations to pressure loss along the retinal arteriolar system.
  
  
  OBJECTIVE
  To examine whether the PAI could predict ocular hypertension (OHT) progression to OAG.
  
  
  METHODS
  The PAI was calculated for 27 eyes of 14 patients with OHT using initial and final digitized optic disc photographs taken during a follow-up interval of 5 to 18 years. Serial stereo color disc photographs and visual fields were analyzed to determine progression.
  
  
  RESULTS
  At baseline, the arteriolar tree of 8 subjects with OHT that progressed to OAG (n = 8 eyes) demonstrated a 45.8% greater mean PAI value than that of 7 subjects who did not progress (n = 7 eyes) (mean +/- SEM, 5.31 +/- 0.93 vs 3.64 +/- 0.34; r = 0.83). Progression was independent of baseline cup-disc ratio. The PAI values of subjects with stable OHT remained stable after a median follow-up interval of 12.0 years. The PAI values of subjects with OHT that progressed demonstrated a further increase of 19.97% +/- 11.24% during a median follow-up period of 6.0 years.
  
  
  CONCLUSIONS
  The results support the hypothesis that low end-arteriolar pressure predicts the progression from OHT to OAG. The PAI provides a new, early, reproducible, and physiological method to study vascular phenomena in glaucoma.
authors.affiliation: Department of Ophthalmology, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada. v.cohen@sympatico.ca
authors.forename: Shawn L
authors.initials: SL
authors.lastname: Cohen
authors.forename: Paul P
authors.initials: PP
authors.lastname: Lee
authors.forename: Leon W
authors.initials: LW
authors.lastname: Herndon
authors.forename: Pratap
authors.initials: P
authors.lastname: Challa
authors.forename: Olga
authors.initials: O
authors.lastname: Overbury
authors.forename: R Rand
authors.initials: RR
authors.lastname: Allingham
mesh_terms: D000328:Adult; D001160:Arterioles; D001794:Blood Pressure / Q000502:physiology; D018450:Disease Progression; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007429:Intraocular Pressure; D009798:Ocular Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D009898:Optic Disk / Q000098:blood supply; D010781:Photography; D012161:Retinal Artery / Q000502:physiology*; D014794:Visual Fields