Agreement of corneal thickness measurement using slitlamp and ultrasound pachymetry

To estimate central corneal thickness (CCT) using a slitlamp biomicroscope and analyze its agreement with ultrasonic pachymetry.

Based on the clinical estimation of CCT on slitlamp examination, 133 eyes of 123 patients were assigned to 3 groups: CCT less than 500 μm, 500 to 600 μm, and greater than 600 μm. An average of three readings was obtained for each patient using an ultrasound pachymeter.

The primary diagnoses at the time of presentation were glaucoma (42, 31.5%), corneal opacity (20, 15%), keratoconus (14, 10.5%), corneal edema (14, 10.5%), and postkeratoplasty eyes (8, 6%). Thirty-five (26.5%) eyes had no known ophthalmic diseases. There was an overall agreement of 86.5% in qualifying CCT into each of the 3 groups (kappa 0.76). The sensitivity and specificity of clinical estimation of CCT were found to be 96.26% (95% confidence interval [CI], 76.1%-94.2%) and 92.31% (95% CI, 78.7%-92.2%), respectively. The agreement was highest in patients with corneal edema (100%, kappa 1.00) and postkeratoplasty eyes (100%, kappa 1.00). The agreement was 82.9% (kappa 0.3) in normal eyes.

Estimation of CCT by slitlamp examination is a reliable tool in clinical practice. In our study, there was a substantial agreement between clinically estimated CCT and ultrasonic pachymetry. This agreement was higher in eyes with abnormal corneal thickness compared with normal eyes.