Dynamic contour tonometry: a new way to assess intraocular pressure in ectatic corneas.

PURPOSE

To compare intraocular pressure (IOP) measurements in patients with keratoconus (KC), pellucid marginal degeneration (PMD), and unilateral penetrating keratoplasty (PK) for KC by Goldmann applanation tonometry (GAT), Tono-Pen tonometry (TP), and Pascal dynamic contour tonometry (DCT).

METHODS

Patients with KC, PMD, or PK were included in a prospective study. IOPs were measured by GAT, TP, and DCT. Severity of ectasia was determined by the steep curvature by corneal topography and central thinning by contact ultrasound pachymetry. IOP measurements were compared and correlated with disease severity.

RESULTS

Fifty-three eyes of 36 patients were enrolled. Mean age was 45.3 +/- 12.5 years (range: 28-72 years). Twenty-nine eyes had KC, 21 eyes had a PK for KC, and 3 eyes had PMD. Mean DCT, GAT, and TP readings were 16.1 +/- 2.9, 14.3 +/- 4.1, and 13.8 +/- 4.1 mm Hg, respectively. The differences of mean IOP between GAT and DCT and TP and DCT were statistically significant, whereas the difference between GAT and TP was not. Both GAT and TP readings were significantly higher in the PK eyes than the KC and PMD eyes, whereas DCT readings were not. DCT measurements were not significantly different in PK versus non-PK eyes.

CONCLUSION

DCT is a newly Food and Drug Administration (FDA)-approved device that is designed to measure IOP, independent of corneal thickness, corneal curvature, and ocular rigidity. DCT gave significantly higher IOP readings than GAT and TP in this study. DCT readings were not affected by corneal thickness. DCT may be more accurate in IOP measurement in eyes with KC and PMD.