Comparison of iCare tonometer and Goldmann applanation tonometry in normal corneas and in eyes with automated lamellar and penetrating keratoplasty

Abstract

Purpose To compare intraocular pressure (IOP) measurements with Goldmann applanation tonometry (GAT) and iCare tonometry in normal and post-keratoplasty corneas and to assess the influence of central corneal thickness (CCT), corneal curvature (CC), and corneal astigmatism (CA) on IOP. Methods This prospective cross-sectional study included one eye of 101 subjects with normal corneas (58 healthy subjects, 43 glaucoma); and 90 post-keratoplasty patients: 34 penetrating keratoplasties (PK); 20 automated-lamellar-therapeutic keratoplasties (ALTK); 19 Descemet-stripping-automatedendothelial keratoplasties (DSAEK); 17 edematous grafts. All subjects underwent GAT and iCare IOP measurements in random order, and CCT, CC, and CA evaluation. The Bland-Altman method and multivariate regression analysis were used to assess inter-tonometer agreement and the influence of CCT, CC, and CA on IOP.Results iCare significantly underestimated IOP in all groups compared with GAT (GAT minus iCare of 3.5±3.5 mm Hg, Po0.001), but overestimated IOP in the edematous grafts (GAT minus iCare of À6.5 ± 1.9 mm Hg, Po0.001). In normal corneas, both tonometer measurements were directly related to CCT values; iCare readings appeared inversely related to CC. There was no significant relationship between IOP and CCT, CC and CA in post-keratoplasty eyes, except between CC and iCare measurements for PK eyes. Conclusions The agreement between GAT and iCare was clinically acceptable in control, ALTK and DSAEK groups, and poor in PK and edematous grafts eyes. In normal corneas, GAT was significantly affected by CCT; iCare was influenced by CCT and CC. The iCare appeared less influenced by corneal edema when compared with GAT. High IOP readings taken with both tonometers in grafts should raise suspicion of true elevated IOP.

Comparability of Icare Pro Rebound Tonometer with Goldmann Applanation and Noncontact Tonometer in a Wide Range of Intraocular Pressure and Central Corneal Thickness

“…Strikingly, Sahin et al [18] found an IOP increase of 1 mm Hg and 8 mm Hg for every 100-µm increase in CCT for the IRT and the GAT, respectively. In the present study, the deviation of the IRT readings from the GAT is only 0.097 mm Hg for every 10 µm of CCT and is comparable with the work of Salvetat et al [19] who reported a deviation of 0.09 mm Hg for every 10-µm increase in CCT. Perhaps, biomechanical properties of the cornea, namely corneal hysteresis and corneal resistance factor, are more influential on the IRT measurements than CCT [20,31,32,33].…”

“…Iliev et al [2] reported a mean difference of 1.0 ± 2.17 mm Hg (95% limit of agreement: -3.2 to 5.2) in their mixed group of patients with minor complaints and open-angle glaucoma; Kim et al [7], in their study group with various pathologies, found a mean difference of 1.92 ± 3.29 mm Hg (95% limit of agreement: -4.52 to 8.37) between the IRT and the GAT; Salim et al [15] reported a mean difference of 2.45 ± 2.12 mm Hg (95% limit of agreement: -1.79 to 6.69) in their study group consisting of glaucoma patients only; Martinez-de-la-Casa et al [16] found a median difference of 1.8 ± 2.8 mm Hg (95% limit of agreement -3.7 to 7.3) in their group consisting of subjects with glaucoma and controls; in a study of normal population, Fernandes et al [17] reported a mean difference of 1.34 ± 2.03 mm Hg (95% limit of agreement: -2.64 to 5.31) between the 2 devices. Conversely, the mean IRT was significantly lower than the GAT, with statistical significance, in a study of normal eyes and eyes with primary open-angle glaucoma [19]. Eyes with glaucoma had a higher mean IOP difference between the GAT and the IRT than healthy eyes, in this study.…”

Retinal oxygen metabolism in healthy subjects and glaucoma patients

“…In Iceland, IOP was measured with iCare TAO1 tonometer (Tiolat Oy, Helsinki, Finland). Comparisons have shown that IOP readings with iCare are clinically reproducible12 and in agreement with those obtained by Goldmann applanation tonometry 13–15…”

Comparison Of Goldmann Applanation Tonometry and Icare Rebound Tonometry In Eyes With Different Corneal Thicknesses

“…Conversely, another study demonstrated that mean IOP measurement was significantly lower with RBT device compared with GAT in study of normal eyes and eyes with primary open-angle glaucoma (18). This study also found that IOP readings with RBT and GAT were significantly directly related to CCT in subjects with normal cornea.…”