Central corneal thickness and Diaton transpalpebral tonometry
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Background To examine the effects of central corneal thickness on the measures obtained from transpalpebral tonometry (Diaton), and to identify correlations between intraocular pressure (IOP) measurements with Diaton and the Goldmann applanation tonometer (GAT). Methods In this cross-sectional study, 162 eyes of 81 participants were included. Intraocular pressure measurements were obtained in all patients using Diaton and GAT. Central corneal thickness was determined by ultrasound pachymetry. The participants were stratified by corneal thickness: group I < 530 mu m (n=56), group II 530-560 mu m (n=65), and group III > 560 mu m (n=41). Results There were moderate correlations between IOP readings obtained using the Diaton and corrected GAT (C-GAT) (r=0.303; P < 0.0001), and between corrected Diaton (C-Diaton), and C-GAT (r=0.399; P0.0001). The mean Diaton tonometer readings were lower than C-GAT measurements (Diaton-corrected GAT mean difference, 0.9 +/- 3.8 mmHg; c-Diaton-corrected GAT mean difference, 0.7 +/- 3.5 mmHg). Differences were detected between the groups of patients for the GAT values [2.4 +/- 3.6 mmHg for those with the thinnest corneas (< 530 mu m), 0.7 +/- 3.6 mmHg for those with moderate corneas (between 531 mu m and 560 mu m), and -0.6 +/- 3.6 mmHg for those with the thickest (> 560 mu m) corneas], whereas a significantly lower difference (0.9 +/- 3.8 mmHg) was noted for the Diaton values of all individuals. Conclusions The Diaton measurements show moderate correlation with those provided by applanation tonometry. The Diaton tonometer seems to be more affected by the corneal thickness, especially in the thinnest corneas.