A Study Of Correlation Between Central Corneal Thickness And Intra Ocular Pressure Measurement Using Goldmann Applanation Tonometer And Rebound Tonometer

Abstract

Introduction: The purpose of this study was to note the influence of central corneal thickness on the intraocular pressure measurementand to compare rebound tonometer and Goldmannapplanation tonometerduring the recent 2 years in Ophthalmology OPD of JSS Hospital. Objectives:  To compare rebound tonometer and Goldmannapplanation tonometer  Influence of central corneal thickness on the intraocular pressure measurement Methodology:A total of 409 patients inclusive of normal controls, proven glaucoma cases and glaucoma suspects were evaluated prospectively, from October 2010 to June 2012. They were studied for their presentation, clinical features and intraocular pressure readings and central corneal thickness were measured. Results: A total of 797 eyes were included in the study. 199 eyes were examined under glaucoma group, out of which 33 patients had closed angle glaucoma and 166 had open angle glaucoma. Majority of the patients in the study population were males in both control and glaucoma group (54.03%). In the glaucoma group consisting of proven glaucoma cases and glaucoma suspects majority had open angle (83.41%). More number of participants belonged to the age group of 40-50 years (45%). The highest mean GAT, RBT and CCT values were obtained for the age group between 61-70 years. The minimum intraocular pressure value obtained using rebound tonometer was 9 mm Hg and maximum value was 56 mm Hg in the entire study group. The minimum intraocular pressure value obtained using Goldmannapplanation tonometer was 8 mm Hg and maximum value was 50 mm Hg in the entire study group. The minimum value for central corneal thickness was 443µm and maximum value was 675µm for the entire study group. For the entire study group intraocular pressure values obtained by rebound tonometer(14.81±2.81mm Hg in normal group and 20.55±8.74mm Hg In glaucoma group) was more than Goldmannapplanation tonometer (14.47±2.98mm hg and 19.88±8.74mm Hg). For central corneal thickness ≤ 530µm, Rebound tonometer values were more than Goldmannapplanation tonometer values in both control and control group. The mean difference was 0.4± 3.9mm Hg and 0.3 mm Hg which was not statistically significant (p values-0.74, 0.792). For central corneal thickness ≥ 531µm, Rebound tonometer values were less than Goldmannapplanation tonometer values in both control and control group. The mean difference was 0.0811mm Hg and0.96 mm Hg which was not statistically significant (p values-0.811,0.93). At higher corneal thickness, Goldmannapplanation tonometer gave higher values than rebound tonometer but the difference was not statistically significant. As the central corneal thickness increased the intraocular pressure value recorded by both the tonometers increased. Conclusion:Central corneal thickness can influence the intraocular pressure recordings of both rebound tonometer and Goldmannapplanation tonometer and thicker corneas yield higher intraocular pressure values. Therefore correction for central corneal thickness will provide a more accurate IOP reading and aid...