Diagnostic Efficacy of Normalization of Corneal Deformation Variables by the Intraocular Pressure in Glaucomatous Eyes

To analyze the diagnostic efficacy of normalization of corneal deformation variables by the IOP in healthy, primary-angle closure (PACG), and primary open angle glaucoma (POAG) patients. Fifty-nine healthy, 83 POAG, and 57 PACG eyes, matched for age and pachymetry, were included in a prospective, observational, cross-sectional study. Goldmann applanation tonometry (GAT-IOP), Corvis-ST IOP, IOPg (Goldmann correlated), and IOPcc (cornea compensated) from the ocular response analyzer were acquired. Corneal hysteresis (CH) and corneal resistance factor (CRF) from the ORA, and deformation amplitude (DA) from Corvis-ST were analyzed. Further, ratios of CH, CRF, and DA to IOP were assessed among the groups and defined as new variables (e.g., ratio [CH, IOPcc] was the ratio of CH to IOPcc). Goldmann applanation tonometry-IOP, IOPcc, and IOPg of PACG and POAG eyes were significantly higher than normal (P < 0.05). Corvis-ST IOP of healthy eyes was similar to POAG (P > 0.05) but lower than PACG (P = 0.02). Corneal hysteresis and CRF of PACG and POAG were significantly lower than normal (P < 0.0001). The ratio (CH, IOPcc), ratio (CRF, IOPcc), and ratio (DA, IOPcc) of healthy eyes were significantly higher than those of PACG and POAG eyes (P < 0.0001). The sensitivity and specificity of ratio (CRF, IOPcc) and ratio (DA, IOPcc) was significantly better than CRF and DA alone in PACG eyes (P < 0.001). However in POAG, only the sensitivity and specificity of ratio (DA, IOPcc) was significantly better than DA alone (P < 0.001). Presence of glaucoma may be indicated better by ratio variables than by CH, CRF, or DA alone.