Tonometry in corneal edema after cataract surgery: dynamic contour tonometry versus Goldmann applanation tonometry

INTRODUCTION: Intraocular pressure (IOP) determination using dynamic contour tonometry (DCT) has been considered to be independent of central corneal thickness (CCT), while Goldmann applanation tonometry (GAT) is known to be influenced by various corneal properties. In this study, IOP was measured before and 1 day after cataract surgery using GAT and DCT to investigate the possible effects of corneal edema on IOP measurements. METHODS: Thirty patients with advanced cataracts were included in a pilot study. IOP was measured using GAT and DCT before and 1 day after phacoemulsification. CCT was determined before and after surgery to quantify postsurgical corneal edema. RESULTS: CCT increased significantly (by 89.7 ± 107.4 μm, P < 0.0001) 1 day after surgery. No significant difference was found for IOP measurements using GAT and DCT before surgery (mean IOP GAT: 17.5 ± 5.7 mmHg; mean IOP DCT: 17.9 ± 6.4 mmHg; P = 0.67) and 1 day after surgery (mean IOP GAT: 16.1 ± 6.6 mmHg; mean IOP DCT: 16.8 ± 8.3 mmHg; P = 0.69). IOP values using GAT and DCT were significantly correlated before as well as 1 day after surgery (before surgery: r = 0.82, P < 0.0001; after surgery r = 0.83, P < 0.0001). Bland–Altman plots showed a high variability in the difference in IOP measurements between methods before and 1 day after surgery. CONCLUSION: GAT and DCT seem to be equally valuable in IOP determination in postsurgical central corneal edema, although large differences between both methods are present in individual patients. IOP evaluation in corneal edema remains a difficult clinical challenge.