title: Pressure-cornea-vascular index (PCVI) for predicting disease progression in normal tension glaucoma.
abstract: BACKGROUND
  It has been shown that the pressure-to-cornea index (PCI), which estimates the relative effects of intraocular pressure (IOP) and central corneal thickness (CCT), may differentiate between glaucoma and non-glaucoma states. The authors investigated the utility of the pressure-cornea-vascular index (PCVI) in predicting field-progression in patients with normal tension glaucoma (NTG).
  
  
  METHODS
  PCVI was constructed from PCI (maximum IOP/CCT(3)) extended with risk factors identified as associated with field-progression in a prospective NTG cohort. Receiver operator characteristics and area under the curve (AUC) of a range of constructs were calculated to arrive at an optimal PCVI.
  
  
  RESULTS
  415 eyes from 415 NTG subjects (184 field-progressed and 231 field-stable) with 3 years of follow-up were analysed. The construct PCVI=(maximum pretreatment office IOP × age at presentation × vertical cup-to-disc ratio at presentation × (1.5 if presence of systemic hypertension; 2.5 if presence of disc haemorrhage; 3.5 if presence of both; 1.0 if none))/(CCT(3)×100) (CCT in mm) gave the highest AUC at 0.71 (95% CI 0.66 to 0.76, p<0.001). The mean PCVI were 113.1±76.8 and 69.7±39.7 for progressed and stable NTG groups, respectively (p<0.001).
  
  
  CONCLUSIONS
  PCVI may be useful for predicting progression in NTG with a satisfactory AUC comparable to established scoring systems in neurovascular medicine. Validation of PCVI in other NTG cohorts, preferably of different ethnicity, is necessary. Trial registration number NCT00321386.
authors.affiliation: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, 2/F, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong. dexleung@alumni.cuhk.net
authors.forename: Dexter Y L
authors.initials: DY
authors.lastname: Leung
authors.forename: Milko E
authors.initials: ME
authors.lastname: Iliev
authors.forename: Poemen
authors.initials: P
authors.lastname: Chan
authors.forename: Nafees
authors.initials: N
authors.lastname: Baig
authors.forename: Stanley C C
authors.initials: SC
authors.lastname: Chi
authors.forename: Clement C Y
authors.initials: CC
authors.lastname: Tham
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D003315:Cornea / Q000473:pathology / Q000502:physiology*; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D018450:Disease Progression; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D057066:Low Tension Glaucoma / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D008875:Middle Aged; D008954:Models, Biological; D009798:Ocular Hypertension / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012166:Retinal Hemorrhage / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D012307:Risk Factors