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.

Repeatability of corneal and epithelial thickness measurements with anterior segment optical coherence tomography in keratoconus

“…In the present study, there was no clear pattern of lower repeatability in the peripheral corneal measurements, which suggests that the REVO-NX AS-OCT generates more consistent peripheral corneal and epithelial thickness measurements. However, the ICC values of central and peripheral CT and ET using REVO-NX were similar when compared to SD-OCT and AS-OCT coupled with placido disc technology [29,30]. Therefore, whilst the REVO-NX generated more consistent measurements across the central and peripheral cornea, the repeatability of measurements compared to other devices should be directly compared and investigated in future studies.…”

“…Several studies have reported lower CT repeatability in the peripheral cornea compared to the central cornea using optical, ultrasound, and Visante OCT devices [28,29]. Dutta et al speculated that this is likely due to the increase in thickness towards the limbus which generates more variable measurements [28].…”

Effect of Demographic Variables on the Regional Corneal Pachymetry

“…Finally, the reproducibility of whole-corneal thickness mapping shows values comparable to previous OCT studies. 28 The superior reproducibility of OCT-based techniques likely relates to an element of enhanced precision and lesser dependence on examiner expertise in comparison with other methods such as ultrasound pachymetry, 1,2 thus supporting the role of SD-OCT in the diagnosis of corneal disease and preoperative management before corneal surgery.…”