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Clinical science
Original article
Pressure–cornea–vascular index (PCVI) for predicting disease progression in normal tension glaucoma
  1. Dexter Y L Leung1,
  2. Milko E Iliev2,
  3. Poemen Chan1,
  4. Nafees Baig1,
  5. Stanley C C Chi1,
  6. Clement C Y Tham1,
  7. Dennis S C Lam1
  1. 1Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Kowloon, Hong Kong, The People's Republic of China
  2. 2Department of Ophthalmology, University of Bern, Inselspital, Bern, Switzerland
  1. Correspondence to Dr Dexter Y L Leung, Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, 2/F, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong; dexleung{at}alumni.cuhk.net

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/CCT3) 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))/(CCT3×100) (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).

Conclusion 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.

  • Normal glaucoma pressure risk
  • intraocular pressure

https://doi.org/10.1136/bjo.2009.175992

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    Footnotes

    • Competing interests None.

    • Patient consent Obtained.

    • Ethics approval This study was conducted with the approval of the Research Ethics Committee (Kowloon East/Kowloon Central Cluster), Hospital Authority, Hong Kong. The study followed the principles in the Declaration of Helsinki and International Conference on Harmonisation – Good Clinical Practice (ICH-GCP) guidelines.

    • Provenance and peer review Not commissioned; externally peer reviewed.