The impact of central corneal thickness on intraocular pressure among Ethiopian glaucoma patients: a cross-sectional study

BACKGROUND Raised intraocular pressure (IOP) is the only causal risk factor for glaucoma that can be therapeutically manipulated to change the course of the disease process. Though Goldman applanation tonometry (GAT) is the "gold standard" for IOP measurement, readings of IOP with GAT are affected by central corneal thickness (CCT). The aim of this study is to determine the impact of CCT on IOP among Ethiopian glaucoma patients. METHODS It was a multicenter cross-sectional study and all glaucoma patients visiting their respective eye clinic during the study period were included. A total of 199 randomly selected glaucomatous eyes from 199 patients aged 18 years and above were employed. The CCT was measured by OcuScan™ RxP Ophthalmic Ultrasound and IOP was measured with Goldmann applanation tonometer. Linear regression and bivariate correlation analysis were carried out and level of significance was taken at 5%. RESULTS The mean IOP was 19.46(± 7.05) mmHg and mean CCT was 508.07(± 33.26) μm. The mean IOP for primary open angle glaucoma (POAG), ocular hypertension (OHT), normal tension glaucoma (NTG), pseudoexfoliative glaucoma (PXG) and primary chronic angle closure glaucoma (PCAG) patients was 19.22 mmHg, 21.39 mmHg, 14.33 mmHg, 33.25 mmHg and 14.75 mmHg respectively. The mean CCT values were 502.24 μm (POAG), 524.32 μm (OHT), 500.75 μm (NTG), 579.00 μm (PXG) and 530.25 μm (PCAG). Age of the patient and glaucoma surgery had an influence on corneal thickness. A positive relationship was found between CCT and IOP (p<0.001). CONCLUSIONS The mean CCT of Ethiopian glaucoma patients is thin in comparison to other ethnic groups and patients with OHT have thicker corneas than POAG patients. Hence determination of CCT for each patient is necessary in the up-to-date glaucoma management.