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).
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.