Non-Contact and Contact Tonometry in Corneal Edema

Abstract

Purpose To compare the intraocular pressure (IOP) values by Goldmann applanation tonometry (GAT) and Reichert 7 CR noncontact tonometry (R7CR-NCT) in patients with postsurgical corneal edema and to examine the impact of postoperative corneal edema on these values.

Methods Forty-six patients with grade 4 and 5 cataracts were included in this study. Intraocular pressure was measured using GAT and R7CR-NCT before and 1 day after phacoemulsification. Central corneal thickness (CCT) was determined before and after surgery to quantify postsurgical corneal edema. The R7CR-NCT provided a Goldmann-correlated IOP (IOPg) and corneal-compensated IOP (IOPcc).

Results The CCT increased significantly 1 day after surgery (the mean preoperative CCT, 543.5 25.4 m; the mean postoperative CCT, 681.5 +/- 19.8 m; p < 0.001), a mean increase of 26.7%. The preoperative R7CR-NCT measurements (the mean IOPcc, 18.8 +/- 5.6 mm Hg; the mean IOPg, 17.8 +/- 4.5 mm Hg) were significantly higher than GAT measurements (the mean GAT-IOP, 16.0 +/- 3.4 mm Hg) (p < 0.001). On postoperative day 1, the R7CR-NCT measurement (the mean IOPcc, 27.0 +/- 9.8 mm Hg; the mean IOPg, 25.1 +/- 8.9 mm Hg) were significantly higher than GAT measurements (the mean GAT-IOP, 18.3 +/- 7.9 mm Hg) (p < 0.001). The difference between postoperative R7CR-NCT and GAT-IOP values were significantly higher than the difference between preoperative R7CR-NCT and GAT-IOP values (p < 0.001 for both IOPcc to GAT-IOP and IOPg to GAT-IOP). The difference between postoperative IOPcc and GAT-IOP was significantly correlated to the change in CCT (r = 0.526, p < 0.001). Similarly, the difference between postoperative IOPg and GAT-IOP was significantly correlated to the change in CCT (r = 0.536, p < 0.001).

Conclusions The R7CR-NCT IOP values were high in patients with postsurgical intensive corneal edema. Consequently, the difference between R7CR-NCT IOP and GAT-IOP increased in edematous corneas.