Assessment of central corneal thickness in normal, keratoconus, and post-laser in situ keratomileusis eyes using Scheimpflug imaging, spectral domain optical coherence tomography, and ultrasound pachymetry.

PURPOSE: To compare the central corneal thickness (CCT) in normal eyes, eyes with keratoconus, and eyes after laser in situ keratomileusis (LASIK) using 3 methods.

SETTING

Cornea Clinic, Grewal Eye Institute, Chandigarh, India.

METHODS

In this study, CCT was measured by sequential Scheimpflug imaging, spectral-domain anterior segment optical coherence tomography (AS-OCT), and ultrasound (US) pachymetry.

RESULTS

Each of the 3 groups comprised 50 eyes. There were no differences between the 3 groups in age, sex, or intraocular pressure. In normal eyes, CCT was statistically significantly higher by US pachymetry (mean 525.8 microm +/- 41.4) [SD] than by Scheimpflug imaging (mean 519.4 +/- 40.9 microm) and AS-OCT (mean 517.9 +/- 41.5 microm) (both P<.001). In keratoconus eyes, CCT by US pachymetry (mean 446.4 +/- 57.9 microm) was statistically significantly higher than by Scheimpflug imaging (mean 439.6 +/- 62.1 microm) (P = .002) and AS-OCT (mean 441.8 +/- 58.4 microm) (P = .007). In post-LASIK eyes CCT by US pachymetry (mean 462.4 +/- 44.7 microm) was significantly higher than by Scheimpflug imaging (mean 457.9 +/- 33.6 microm) (P = .012) and AS-OCT (mean 455.4 +/- 43.2 microm) (P<.001). In all groups, CCT measured by Scheimpflug imaging and AS-OCT was similar.

CONCLUSIONS

There was a statistically significant difference between Scheimpflug imaging and US pachymetry and AS-OCT, with US pachymetry measurements being consistently thicker. Thus, CCT should be interpreted in the context of the instrument used.