Repeatability of Scheimpflug Corneal Tomography in Patients with Keratoconus and Different Body Mass Indices

Objective: To evaluate the repeatability of corneal tomographic parameters in keratoconus patients across different body mass index (BMI) categories. Methods: This prospective study was conducted at the University of Auckland, New Zealand, from June 2021 to June 2022. A total of 243 eyes from keratoconus patients aged 18-45 years were categorized into normal (BMI ≤24.9; n=55), overweight (BMI 25.0-29.9; n=58), and obese (BMI ≥30.0; n=130) groups. Patients underwent three consecutive scans using the Pentacam AXL. The repeatability of flat simulated keratometry (K1A), steep simulated keratometry (K2A), maximum keratometry (Kmax), central corneal thickness (CCT), and thinnest corneal thickness (TCT) was assessed using within-subject standard deviation (Sw), repeatability limits, and intraclass correlation coefficients (ICC). A subgroup analysis was performed by matching patients for keratoconus severity to assess the influence of disease stage on repeatability. Results: Repeatability decreased significantly with higher BMI across all parameters. K1A and K2A had the highest repeatability (ICC 0.992-0.998), while TCT had the lowest (ICC 0.983-0.988). Notably, the obese group showed greater variability in CCT and TCT compared to the normal and overweight groups. After adjusting for keratoconus severity, these differences were no longer statistically significant between BMI groups. Conclusions: Tomographic parameter repeatability in keratoconus patients is excellent across BMI categories. Although repeatability decreases with increasing BMI, this effect is not significant after accounting for disease severity. These findings underscore the importance of using the most reliable tomographic parameters for monitoring keratoconus progression, particularly in patients with higher BMI and advanced stages of the disease.