[Evaluation of dynamic contour tonometry in penetrating keratoplasties]

The PASCAL dynamic contour tonometer (DCT) adapted to the corneal geometry is a new approach for digital measurement of intraocular pressure (IOP). The purpose of this study was to evaluate the DCT vs Goldmann applanation tonometry (GAT) in penetrating keratoplasties.

We included 92 consecutive eyes after penetrating keratoplasty (57 without sutures, 32 with 2 running sutures, 3 with 1 running suture) in this prospective cross-sectional study. The mean outcome measurements were central corneal power (Zeiss ophthalmometer) and central corneal thickness (ultrasound pachymetry Tomey AL-1000). IOP was evaluated in consecutive measurements including 3x DCT and 1x GAT.

The mean IOP measured with DCT was 18.3+/-4.0 mmHg in contrast to GAT with 14.3+/-4.1 mmHg (p<0.001). Both methods showed a strong correlation of IOP values (r=0.74, p<0.001). The quality of measurement in keratoplasties after complete suture removal was between Q1 and Q3 in 88% with DCT in contrast to 59% with two running sutures. Three values with a reproducibility of 0.97 (Cronbach's alpha) could be obtained in 53 eyes without sutures and with a reproducibility of 0.94 (Cronbach's alpha) in 20 eyes (62.5%) with 2 running sutures. DCT or GAT did not correlate with central corneal thickness. The mean astigmatism did not differ between keratoplasties without sutures (4.86+/-3.35 D) or with two running sutures (4.2+/-2.8 D, p=0.38).

The DCT provides reproducible IOP measurements in penetrating keratoplasties with significantly higher values in comparison to GAT. Nevertheless, as known for GAT, postoperative intrastromal corneal sutures after penetrating keratoplasty disturb the exact DCT measurement as well.