Comparison of Corneal Tomography: Repeatability, Precision, Misalignment, Mean Elevation, and Mean Pachymetry.

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Medical Imaging

Background:

• Corneal tomography is crucial for diagnosing and monitoring eye conditions.
• Accurate and precise measurements are essential for effective clinical decision-making.
• Understanding the performance of different tomographic devices is vital for reliable patient care.

Purpose of the Study:

• To compare the precision and repeatability of corneal tomography measurements from three devices: Pentacam HR, CASIA SS-1000, and TMS-5.
• To evaluate the statistical uncertainty associated with each tomographer's data.
• To assess the interchangeability of data generated by these clinically used systems.

Main Methods:

• Utilized repeated measurements on 34 normal eyes for each of the three corneal tomographers.
• Estimated repeatability (standard deviation) and precision (corrected for misalignment) for corneal elevation and pachymetry maps.
• Applied Zernike polynomial fitting to mean data-maps for inter-device comparison.

Main Results:

• Pentacam HR demonstrated superior repeatability and precision for anterior corneal elevation (<3 µm and <1.6 µm).
• CASIA SS-1000 showed excellent repeatability and precision for posterior corneal elevation and the best repeatability for pachymetry (<3 µm).
• TMS-5 exhibited similar anterior elevation repeatability to CASIA SS-1000 (<6 µm), but data-maps were not interchangeable, with significant differences in pachymetry and posterior elevation.

Conclusions:

• Device-specific misalignment significantly impacted the repeatability of TMS-5 and Pentacam HR, but not CASIA SS-1000.
• The performance variations indicate that data from these tomographers cannot be directly interchanged for clinical use.
• Choosing the appropriate tomographer depends on the specific measurement priority (e.g., anterior vs. posterior cornea, pachymetry).