Comparing central corneal thickness among primary open angle glaucoma and non-glaucoma patients at the university teaching hospitals eye hospital, Lusaka, Zambia.

Abstract

Background: Intraocular pressure (IOP) remains the only modifiable risk factor in the management of glaucoma. Accurate measurement of IOP is key in determining individuals at risk of glaucoma. Goldmann applanation tonometry (GAT) is the gold standard method for measuring IOP. In designing the GAT, it was assumed that the Central Cornea Thickness (CCT) was constant at 520 μm. CCT has been noted to vary greatly from one race to another and from one individual to another. The study compared CCT among POAG and non-glaucoma patients, and evaluated the correlation of CCT with Humphrey Visual Field (HVF) parameters (Mean Deviation (MD), Pattern Standard Deviation (PSD)) and Retinal Nerve Fibre Layer (RNFL) thickness based on Spectral Domain Optical Coherence Tomography (SD-OCT) in Primary Open Angle Glaucoma (POAG) patients. Objective: To determine if there is a difference in the central corneal thickness between patients with Primary Open Angle Glaucoma (POAG) and non-glaucoma patients. Methodology: A cross-sectional study was conducted in 2020 from February to March. The participants who met the inclusion criteria were POAG and non-glaucoma patients attending the University Teaching Hospitals – Eye Hospital during the study period. Using simple random sampling, patients were aged 40 years and above were recruited. Ophthalmic history was taken and a comprehensive eye examination done on all participants. The CCT was measured using contact ultrasound system and IOP was measured by GAT. Analyses were carried out considering the level of significance at 5%. Results: One hundred six patients were recruited. The mean CCT of the right eye for the POAG patients was 525.19 ± 36.10 μm and non-glaucoma patients was 549.23 ± 35.45 μm. The mean CCT of the left eye for the POAG patients was 527.51 ± 42.71 μm and for the non-glaucoma was 546.91 ±34.91 μm. We found no significant correlation between CCT and MD, PSD and RNFL (P > 0.05). We found a slight negative correlation between CCT and CDR in the RE (r = -0.28, P = 0.04). Conclusion: There was significant difference in the CCT of POAG and non-glaucoma patients in both the right eyes and left eyes, with CCT being thinner in POAG patients.