Central Corneal Thickness and Its Association with the Severity of Primary Open-Angle Glaucoma

Understanding the relationship between central cornea thickness and glaucoma severity will help in assessing individualised risk and will enhance evidence-based decision-making in the early diagnosis and management of glaucoma.

We aimed to determine the correlation between central corneal thickness (CCT) and the severity of glaucoma at different stages of primary open-angle glaucoma (POAG) at the Federal Medical Centre (FMC), Lokoja, Nigeria.

A cross-sectional study of POAG patients at presentation to FMC, Lokoja. Biodata, use of anti-glaucoma medications, and family history of glaucoma were obtained. Examinations included visual acuity, central visual fields, slit lamp examination, pachymetry, gonioscopy, indirect fundoscopy, and fundus photograph. The correlation between CCT and the above parameters was ascertained. Using the mean deviation, the severity of glaucoma was classified: as mild glaucoma <-6 dB, moderate glaucoma -6 to -12 dB, severe glaucoma -12 to -18 dB, and end-stage glaucoma >-18 dB.

A total of 242 eyes of 121 POAG patients were studied. The male-to-female ratio was 1.5:1. The mean age was 55 ± 10 years (range = 40-78 years). Most (65.7%) had not used anti-glaucoma medications and 17.4% gave a positive family history of glaucoma. There was no clinical correlation between positive family history and CCT (P = 0.71) and no correlation between family history and glaucoma severity (P = 0.96). The patients were classified as mild glaucoma 63(29.9%), moderate glaucoma 95(45%), severe glaucoma 30 (14.2%), and end-stage glaucoma 23 (10.9%). The mean CCT was 508.0 ± 32μm. There was a decrease in CCT from 517.94 ± 26μm in mild glaucoma to 504.96 ± 40μm in end-stage glaucoma; this difference was statistically significant (P = 0.031). The mean intraocular pressure (IOP) was 24 ± 7 mm Hg, whereas the mean corrected IOP was 27 ± 8 mm Hg.

There was a negative significant correlation between CCT and glaucoma severity and between CCT and true IOP. CCT did not correlate with age, sex, family history, or laterality of POAG.