The effect of contact lens-induced corneal edema on Goldmann applanation tonometry and dynamic contour tonometry

Abstract

To evaluate the effect of contact lens-induced corneal edema on intraocular pressure (IOP) measurements using Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) in Asian subjects. The study included 40 eyes of 20 normal volunteers with no evidence of ocular disease. Forty eyes of 20 healthy volunteers were required to wear soft contact lenses for 2 hours to induce corneal swelling. Central corneal thickness (CCT) and IOP were measured before and immediately after contact lens wear using specular microscope, GAT, and DCT. The IOP measurements by GAT and DCT were compared. The changes in the CCT and the IOP measurements after wearing contact lenses were assessed. The mean CCT of the 40 eyes evaluated was 532.6 +/- 31.6 mu m. The mean IOP was 11.78 +/- 2.04 mmHg for the GAT and 14.46 +/- 1.89 mmHg for the DCT, and the difference was statistically significant (P < 0.001). After wearing contact lenses, the mean CCT was 553.2 +/- 34.3 mu m, which was 20.6 +/- 12.9 mu m greater than before wearing them (P < 0.001). The mean IOP measurements of the GAT and DCT were decreased after wearing the contact lenses. The mean decrease of the GAT values was 0.43 +/- 1.95 mmHg, which was not statistically significant (P = 0.175). However, the mean decrease of the DCT readings, which was 0.75 +/- 1.74 mm Hg, was statistically significant (P = 0.010). The IOP measurements with DCT were significantly higher than those with GAT in healthy Asian eyes. Although the mean IOP measurements of both the GAT and the DCT were decreased in the edematous cornea, IOP measurements of the DCT were more affected by corneal edema than were the GAT.