Role of central corneal thickness measurement in management of open angle glaucoma and glaucoma suspects in Calabar, Nigeria

Introduction: Central Corneal Thickness (CCT) is gaining increasing significance in the management of glaucoma patients due to the recognized relationship between CCT and intraocular pressure (IOP) levels. The Objective of this study was to evaluate to what extent CCT modified Goldmann Applanation Tonometry (GAT), and thus management decisions in the care of glaucoma patients and suspects in Calabar, Nigeria. Materials and methods: All consenting patients seen from January to December 2015 in University of Calabar teaching Hospital (UCTH) eye clinic and Zerah Eye Hospital and Laser Center, Calabar who were diagnosed as Glaucoma suspects/patients were included. IOP was measured by Goldmann Applanation Tonometry (GAT), and CCT measured by handheld contact ultrasound pachymetry. Data entry and analysis was performed using STATA 12 software. Results were summarized in frequencies, percentages and means while comparison was done using 95% confidence interval. Results: The study sample was 256 with 133(51%) females and 123(48%) males. The mean age was 45.52years ±17.82. The mean CCT was 530µm. An inverse relationship between CCT and age was seen; mean CCT of 518.29µm and 548.93µm for the oldest age and youngest age groups respectively. Increasing age is a known risk factor for glaucoma, but it remains to be elucidated if the progressive thinning in CCT with age confers an independent risk factor. The mean IOP was 15.835 and CCT adjusted values for IOP varying from -7 to +7 mmHg with mean IOP adjustment of 0.84mmHg ± 2.66mmHg for right eye and mean IOP adjusted value of 0.98mmHg ± 2.69mmHg for the left eye. Over 50% had adjusted IOP values of ≥1.5mmHg, while 36% had adjusted values of ≥3mmHg. Conclusion: Measurement of CCT was important for management decisions as 36% of study subject required IOP adjusted values of ≥3mmHg, thus affecting diagnostic criteria and modifying decisions on ‘Target IOP' during management. Routine CCT measurement at diagnosis should be part of a minimum package of care even in low resource settings, for the glaucoma patients to avoid under-treatment/overtreatment from ‘falsely' elevated or lowered IOPs.