Correlation between Intra Ocular Pressure, Central Corneal Thickness and Glaucoma Stage in Patients with Primary Open Angle Glaucoma

Purpose: To determine the correlation between central corneal thickness (CCT), Intra Ocular Pressure (IOP) and glaucoma stage as assessed by cup to disc ratio (CDR) in patients with primary open angle glaucoma (POAG) Material and Method: Patients with Primary open angle glaucoma were included. Patients under 35 years of age, with some corneal and retinal problems and secondary open angle glaucoma were excluded from study. After ultrasound pachymetry, intraocular pressure was measured using Goldmann applanation tonometry. Cup to disc ratio was assessed and disc photograph taken. Pearson’s correlation coefficients were calculated to assess the associations between central corneal thickness, intra ocular pressure and vertical cup to disc ratio. P value lower than 0.05 was defined as statistically significant. Results: One hundred and fifty three eyes of 86 patients with POAG were examined. Mean corneal thickness was 535 um and mean Intra ocular pressure was 30mmHg. A significant negative correlation was detected between central corneal thickness and cup to disc ratio (r=-0.204, P=0.031). Eighty-eight percent of patients with CCT<500um and 80% patients with CCT 500-519um presented with 0.7 to total cupping but as the CCT increases, this ratio became equal or reverse. Conclusion: Glaucoma patients with thin central corneal thickness are more likely to be found at an advanced stage of the disease. Under estimation of intra ocular pressure by Goldmann applanation tonometry could be one causative factor.