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Back-calculation of keratometer index based on OCT data and raytracing - a Monte Carlo simulation
Achim Langenbucher1, Nóra Szentmáry2,3, Johannes Weisensee1
1Department of Experimental Ophthalmology, Saarland University, Homburg/Saar, Germany.
Acta Ophthalmologica
|February 12, 2021
Summary
This study introduces a raytracing method to accurately calculate corneal power using optical coherence tomography (OCT) data. The new approach determines an individual keratometer index, improving precision beyond traditional methods.
Area of Science:
- Ophthalmology
- Biomedical Optics
- Corneal Biomechanics
Background:
- Traditional keratometry relies on assumptions that may not hold true for all corneas.
- Accurate corneal power calculation is crucial for refractive surgery and intraocular lens implantation.
Purpose of the Study:
- To develop a raytracing strategy for calculating corneal power from anterior segment optical coherence tomography (OCT) data.
- To extract an individual keratometer index for improved corneal power calculation.
Main Methods:
- A large OCT dataset (10,218 eyes) was analyzed using custom MATLAB scripts.
- Raytracing through the cornea was performed using radius of curvature, asphericity, central corneal thickness, and pupil size.
- The keratometer index was back-calculated and analyzed using a multivariate linear model.
Main Results:
- The average keratometer index was 1.3317 ± 0.0017.
- Corneal front surface asphericity was the only significant factor in a univariate model.
- A multivariate model incorporating 6 parameters showed high performance (R²: 0.90, RMS error: 5.54e-4).
Conclusions:
- Classical keratometer index calculations are based on simplifying assumptions.
- Corneal power cannot be accurately determined from front surface radius alone.
- A multivariate model using measured tomographic data provides a more accurate corneal power calculation.
