Variability of CLMI-X parameters, zonal Kmax, and single-point Kmax in keratoconus progression

Area of Science:

• Ophthalmology
• Corneal Imaging
• Keratoconus Research

Background:

• Keratoconus (KC) diagnosis and monitoring rely on accurate corneal measurements.
• Assessing the repeatability of various corneal parameters is crucial for reliable clinical application.
• Existing methods like maximum single point keratometry (Kmax) may have limitations in repeatability.

Purpose of the Study:

• To compare the repeatability of novel corneal parameters: 2mm zone of greatest corneal curvature (Cspot-Axi) and 1mm zone of thinnest pachymetry (Spot-Pach).
• To evaluate these against established metrics: maximum single point keratometry (Kmax), 3mm Zonal Kmax (Z-Kmax3), and thinnest single point pachymetry (TP).
• To determine the most reliable parameters for keratoconus diagnosis and follow-up.

Main Methods:

• A comparative repeatability study involving 36 eyes of normal individuals and 72 eyes of KC patients.
• Corneal imaging was performed six times per eye with breaks to ensure data integrity.
• Within-subject standard deviation (Sw) was calculated for each parameter to assess repeatability.

Main Results:

• In normal and KC groups, Cspot-Axi and Z-Kmax3 showed significantly higher repeatability than Kmax (p < 0.0001).
• The repeatability of Spot-Pach was found to be similar to that of TP across all study groups (p > 0.05).
• Differences in repeatability were statistically significant between Cspot-Axi and Z-Kmax3 in the normal group (p = 0.0482).

Conclusions:

• Zonal averages of Cspot-Axi and Z-Kmax3 offer superior repeatability compared to single point Kmax for KC management.
• Spot-Pach and TP exhibit comparable repeatability, making them equally suitable for clinical use.
• These findings support the use of zonal measurements for more reliable keratoconus assessment.