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M. L. Salvetat, F. Miani, C. Tosoni, L. Parisi, M. Zeppieri, P. Brusini; Comparison of ICare and Goldmann Applanation Tonometry in Normal Subjects and Patients That Underwent Automated Lamellar and Penetrating Keratoplasties. Invest. Ophthalmol. Vis. Sci. 2009;50(13):610.
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To compare the intraocular pressure (IOP) readings taken with Goldmann applanation tonometry (GAT) and ICare tonometry in subjects with normal corneas and in patients that underwent lamellar or penetrating keratoplasty. The influence of central corneal thickness (CCT), corneal curvature (CC) and corneal astigmatism (CA) on IOP measurements were also assessed.
This prospective observational cross-sectional study included 4 groups of subjects (1 eye per patient): 94 subjects with normal corneas (controls); 44 patients that underwent penetrating keratoplasty (PKP); 20 patients that underwent automated-lamellar-therapeutic-keratoplasty (ALTK); and, 22 patients after Descemet-stripping-automated-endothelial-keratoplasty (DSAEK). All subjects underwent GAT and ICare IOP measurements and CCT, CC and CA ultrasound measurements. The agreement between tonometers was assessed using the Bland-Altman method. Multivariate regression analysis was used to evaluate the influence of CCT, CC and CA on IOP measurements.
The mean IOP differences (GAT minus ICare) were 1.7±3.7 mmHg, 1.6±3.5, 1.4±3.1 and 1.2±4.2 in the control, PKP, ALTK and DSEAK groups, respectively. The IOP differences were within ±3 mmHg in 64.5% of eyes. In the control group, GAT and ICare IOP measurements were respectively slightly (p=.07) and significantly (p=.01) related to CCT. The IOP measurements taken with both tonometers were significantly inversely related to CCT in all post-keratoplasty eyes and significantly inversely related to CC in the PKP and ALTK groups; this relationship appeared slightly higher for GAT.
GAT and ICare showed a good inter-method agreement overall, although GAT significantly overestimated ICare measurements in all groups. GAT and ICare overestimated IOP values in thicker corneas in controls, which appeared to be greater for ICare. Both devices underestimated IOP in thick and steep post-keratoplasty corneas, and this tendency was higher with GAT. ICare seemed less dependent on biomechanical properties of post-keratoplasty corneas than GAT, and appeared to be clinically useful in eyes with corneal graft.
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