Rebound, applanation, and dynamic contour tonometry in pathologic corneas.

PURPOSE

To compare the practicability of using an Icare rebound tonometer (RT) versus a Goldmann applanation tonometer (GAT) or a Pascal dynamic contour tonometer (DCT) for measuring intraocular pressure (IOP) in patients with corneal abnormalities and, furthermore, to study the influence of central corneal thickness, corneal diameter, corneal radius, and axial length.

METHODS

One hundred seventy-one pathologic eyes with corneal abnormalities and 26 nonpathologic control eyes of 99 patients were included. Pathologic corneas were divided into subgroups: previous keratoplasty, keratoconus, corneal scars, corneal dystrophies, and bullous keratopathy.

RESULTS

Although IOP was successfully measured using the RT in all pathologic eyes, successful measurement of IOP was only possible in 98.2% when using the GAT and in 73.1% with the DCT. Mean IOP for all enrolled eyes was 12.7 ± 4.1 mm Hg for RT, 15.5 ± 4.4 mm Hg for GAT, and 16.3 ± 4.1 mm Hg for DCT. The mean difference between RT and GAT was ≤ 1 mm Hg (≤ 2 mm Hg) [≤ 3 mm Hg] in 23.4% (41.8%) [62.0%] of cases. Correlation analysis showed a moderate correlation between RT and GAT (r = 0.566; P < 0.001) and between RT and DCT (r = 0.364; P < 0.001). Bland-Altman analysis revealed a bias between RT and GAT and between RT and DCT of -2.8 and -3.8 mm Hg, with limits of agreement of -10.5 to 4.9 mm Hg and -12.2 to 4.6 mm Hg, respectively.

CONCLUSION

In pathologic corneas, IOP was difficult to obtain with GAT and DCT, whereas RT was able to determine IOP in all pathologic corneas. RT significantly underestimated IOP in all groups in relation to GAT and DCT. The agreement between the methods was clinically acceptable in corneal dystrophy and keratoconus but poor in eyes after keratoplasty.