About this tool
Disclaimer: This tool is theoretical and has not been verified in a prospective clinical trial. This calculator is not intended to be a substitute for surgical judgment. Surgeons should always use their own judgment when deciding upon treatment based on all factors available. User discretion is advised. This calculator is designed to aid ophthalmologists in accurately determining the size of an Implantable Collamer Lens (ICL) for their patients. Based on a comprehensive study of measurement variability across different biometric devices, this nomogram adjusts measurements to align with those from the Orbscan II, ensuring consistency and precision in ICL sizing based on the original ICL sizing recommendations.
How to use this calculator:
- Select Your Device: Choose your biometry device.
- Enter Measurements: Input the white-to-white (WTW), anterior chamber depth (ACD) and, if prompted, central corneal thickness (CCT). This calculator will automatically adjust ACD based on the biometer to calculate true ACD (endothelium to anterior capsule).
- Calculate: The nomogram will adjust your measurements based on our study's findings and estimate the most suitable ICL size.
Predicted Vault Calculation
The predicted vault calculation is based on the geometric relationship between the adjusted white-to-white (WTW) measurement, the true anterior chamber depth (ACD), and the ICL size, utilizing theoretical equations like the iterative Newton-Raphson method to determine the radius of curvature. It involves solving for the chord length and arc length, and applying empirical scaling factors to estimate the vault height. While these calculations are based on ideal geometric conditions, they may not always reflect real-world clinical findings due to anatomical variations and measurement discrepancies.
About the calculator and the study:
The original guidelines and nomograms for ICL sizing were developed using data from the Orbscan II. However, with the advent of new-generation biometric devices, variations in measurements have been observed. These discrepancies could potentially impact the accuracy of ICL sizing, thereby affecting surgical outcomes.
Our study, "Assessment of Measurement Variability Across Automated Biometry Devices," involved 408 eyes and sought to understand how measurements from current-generation devices compare to those from the Orbscan II. The goal was to ensure that the advancements in device technology could be seamlessly integrated into existing ICL sizing practices without compromising accuracy.