Reliability of Pentacam HR Thickness Maps of the Entire Cornea in Normal, Post–Laser In Situ Keratomileusis, and Keratoconus Eyes

Abstract

To measure the repeatability and reproducibility of Pentacam HR system thickness maps for the entire cornea in normal, post-laser insitu keratomileusis (post-LASIK), and keratoconus (KC) eyes. Reliability study. Sixty normal subjects (60 eyes), 30 post-LASIK subjects (60 eyes), and 14 KC patients (27 eyes) were imaged with the Pentacam HR system by 2 well-trained operators. For pachymetry the cornea was divided into 4 zones: a central zone (2-mm diameter) and concentric pericentral zone (2-5mm), transitional zone (5-7mm), and peripheral zone (7-10mm). The 3 concentric zones were subdivided into 8 sectors. Intraobserver repeatability and interobserver reproducibility of entire corneal thickness maps were tested by the repeatability and reproducibility coefficients, intraclass correlation coefficients, coefficient of variation, and 95% limits of agreement. From central to peripheral zones, the precision of corneal thickness measurements became gradually smaller. Central zone repeatability and reproducibility were the best in the normal, post-LASIK, and KC groups. The peripheral superior sectors showed poorer repeatability and reproducibility for all subjects. The intraobserver repeatability and interobserver reproducibility for all zones were ≤19.3μm, ≤22.1μm, and ≤20.7μm, in the normal, post-LASIK, and KC groups, respectively. The intraobserver and interobserver coefficients of variation for all zones were ≤1.3%, ≤1.6%, and ≤1.6% for all 3 groups. Pentacam HR system pachymetry of the entire cornea provided good precision in normal, post-LASIK, and KC corneas. Thickness measurements in the peripheral cornea should be interpreted with caution in abnormal corneas after surgery or with diseases.