Comparison of Goldmann Applanation Tonometry and Icare Rebound Tonometry in Eyes of Varied Corneal Thickness

INTRODUCTION: The aim of the present study was to compare intraocular pressure (IOP) level as measured with Goldmann applanation tonometry (GAT) and Icare rebound tonometry (RBT; Icare Finland Oy, Vantaa, Finland) in patients with varied central corneal thickness (CCT).
METHODS: Total of 138 eyes of 138 consecutive patients from glaucoma department were studied. Ultrasound pachymeter was used to measure CCT in all cases and patients were divided into 3 groups according to CCT. Group 1 comprised patients with thin CCT (<520 μ), Group 2 was made up of patients with normal CCT (520-570 μ), and patients with thick CCT (>570 μ) composed Group 3. IOP was measured with RBT, which uses average of 6 readings, followed by GAT. Measurements of groups were compared.
RESULTS: Mean age of patients was 59.4±10.9 years. Mean CCT value was 494.9±15.9 μ in Group 1 (n=40), 549.1±16.3 μ in Group 2 (n=52), and 604.0±22.2 μ in Group 3 (n=46). Mean IOP measurement obtained by GAT and RBT was 13.2±4.0 and 13.8±3.9 mmHg, respectively, in Group 1 (p=0.013), 16.9±3.2 and 16.8±3.1 mmHg in Group 2 (p=0.745), and 18.1±3.4 and 18.4±3.8 mmHg in Group 3 (p=0.359). Mean difference in IOP for entire study group between GAT and RBT was -0.21±1.7 mmHg (p=0.15). This difference was statistically significant only in Group 1 (p=0.013). Positive correlation was found between CCT and measurement via both GAT and RBT (p<0.01). There was no correlation between CCT and difference in IOP obtained by RBT and GAT.
DISCUSSION AND CONCLUSION: Icare RBT demonstrated agreement with Goldmann applanation tonometry, except in thin corneas.