Accuracy of Icare Rebound Tonometer and Its Comparison with Goldman Applanation Tonometer

Purpose:  To determine accuracy of iCare rebound tonometer (IRT) in terms of agreement with Goldman Applanation Tonometer (GAT) and effect of Central corneal thickness (CCT) on its accuracy. Study Design:  Comparative cross sectional study. Place and Duration of Study:  Ophthalmology Department of Ittefaq Hospital Lahore from September 2022 to May 2023. Methods:  Participants of the study were recruited through non-probability convenient sampling. With Icare PRO® rebound tonometer (IRT), two consecutive sets of measurements with 6 measurements for each set were made, and the averaged values were used for the statistical analyses. After 5 minutes GAT measurement was taken for intraocular pressure (IOP). CCT was measured by ultrasound pachymetry from mean of 2 measurements noted. Data was analyzed by Bland-Altman plots for determining agreement of GAT-IOP and IRT-IOP. Pearson correlation coefficient determined the correlation of GAT-IOP and IRT-IOP with CCT. Results:  Out of 200 participants there were 76 (38%) males and 124 (62%) females. Mean age of participants was 27.84 ± 6.1 years. Mean IOP with IRT was 16.24 ± 2.02 (range 12.1 – 20.3 mmHg). Mean IOP with GAT was 14.40 ± 1.98 (range 11.00 – 19 mmHg). Mean IOP with adjusted CCT using GAT was 14.40 ± 1.64 (range 11 – 18 mmHg). Mean CCT was 544.81 ± 42.04 (range 615 – 471 um). Mean IOP-GAT & IOP-IRT with adjusted CCT showed normal distribution. Mean difference of IOP-GAT and IOP-IRT with t test was 1.83 ± 1.12 (p = .079). Conclusion:  There is a strong agreement between IOP-GAT and IOP-IRT. CCT had a strong impact on IOP measurements with both tonometers. However, CCT affected IOP reading of GAT more than IRT.