A Cross-Sectional Study to Evaluate the Usefulness of ‘Pressure to Cornea Index’ in Prediction of Primary Open Angle Glaucoma

Abstract

BACKGROUND The prevalence of glaucoma blindness is about 8% of global blindness and in India is about 4.4%. The Intraocular Pressure (IOP) is a single major modifiable risk factor in glaucoma. In order to integrate IOP and CCT as a single risk factor, a new index 'Pressure-to-Cornea Index' (PCI) was proposed. But studies regarding the fact that the increased values of PCI will be a risk factor for glaucoma are limited. This study attempts to describe the role of PCI as a predictive risk factor in clinical POAG. The aims and objectives of this study are to determine the PCI values in POAG, OHT and NTG and to determine whether PCI can be used as a predictive value in clinical Primary Open Angle Glaucoma (POAG). MATERIALS AND METHODS This observational, cross-sectional type of study was conducted over a period of six months, in 478 eyes of patients attending the outpatient at Govt. Rajaji Hospital, Madurai, who satisfied the inclusion-exclusion criteria. IOP estimation by GAT and CCT measurement by Ultrasound Pachymetry was done in all of them. After routine glaucoma evaluation, they were segregated as Group 1: Normotensives (374), Group 2: Ocular Hypertension (29), Group 3: Normal Tension Glaucoma (28) and Group 4: Primary Open Angle Glaucoma (47). Data collected were entered in Master Chart and statistical analysis was done using software IBM SSPS Ver 21.0 (Armonk, NY) by our statistician. The study groups without clinical POAG are Group 1 and Group 2 (mean PCI value of 92 and 117). The study groups with clinical POAG are Group 3 and Group 4 (mean PCI value of 134 and 171). This study demonstrates a significant correlation between PCI levels and glaucomatous changes in eyes. The PCI value may be also useful in the management of glaucoma for setting a target IOP. RESULTS The obtained 'P' value is < 0.001 which is statistically significant says that there is a difference in the IOP measurements and CCT measurements between the 4 groups (Normal, Ocular Hypertension, Normotensive Glaucoma and Primary Open Angle Glaucoma). CONCLUSION The value of PCI is significantly increased in glaucomatous (POAG and NTG) eyes. This emphasises that PCI can be used as a predictive index in development of glaucomatic changes in optic disc in the population.