Abstract
BackgroundRaised 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.MethodsIt 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%.ResultsThe 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).ConclusionsThe 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.
Highlights
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 most widely used and current “gold standard” for IOP measurement [4], readings of IOP made with GAT are affected by central corneal thickness (CCT) [5]
In this study it was found that the mean CCT and IOP among Ethiopian glaucoma patients were 508.07 μm and 19.46 mmHg respectively
Summary
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. Though Goldman applanation tonometry (GAT) is the most widely used and current “gold standard” for IOP measurement [4], readings of IOP made with GAT are affected by central corneal thickness (CCT) [5]. Studies have shown that there is variation in the mean CCT among individuals with healthy eyes [5,7], in patients with different types of glaucoma [8], and presence of pseudo-exfoliation syndrome [5]. Several studies have suggested 0.014–0.179 mmHg/0.01 mm increase in CCT This small change could be clinically significant especially in individuals predisposed to glaucoma [9,10]. Failure to adjust IOP for CCT variation could lead to inappropriate targeting of IOP and setting targets very high for patients having thinner corneas and very low for those with thicker corneas
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