Reliability of Entire Corneal Thickness Mapping in Normal Post-Laser in situ Keratomileusis and Keratoconus Eyes Using Long Scan Depth Spectral Domain Optical Coherence Tomography

Abstract

Purpose: To investigate the repeatability and reproducibility of mapping the entire corneal thickness using spectral domain optical coherence tomography (SD-OCT). Methods: Thirty normal eyes, 30 post-laser in situ keratomileusis (LASIK) surgery eyes, and 30 keratoconus eyes were analyzed. A custom-built long scan depth SD-OCT device was used to obtain entire corneal images. Ten-millimeter-diameter corneal thickness maps were generated by an automated segmentation algorithm. Intraclass correlation coefficients of repeatability (ICC₁) and reproducibility (ICC₂), and coefficients of repeatability (CoR₁) and reproducibility (CoR₂), were calculated to quantify the precision and accuracy of corneal pachymetry measurements using the Bland-Altman method. Results: For SD-OCT measurements in healthy subjects, CoR₁ and CoR₂ were less than 5.00 and 5.53 μm. ICC₁ and ICC₂ were more than 0.997 and 0.996. For SD-OCT measurements in LASIK patients, CoR₁ and CoR₂ were less than 5.09 and 5.34 μm. ICC₁ and ICC₂ were more than 0.997 and 0.996. For SD-OCT measurements in keratoconus patients, CoR₁ and CoR₂ were less than 11.57 and 10.92 μm. ICC₁ and ICC₂ were more than 0.995 and 0.996. Conclusions: The measurements of corneal pachymetric mapping by long scan depth SD-OCT can be assessed over the entire corneal area with good repeatability and reproducibility.