Update on Biometry and Lens Calculation - A Review of the Basic Principles and New Developments

Area of Science:

• Ophthalmology
• Optical Engineering
• Medical Biometry

Background:

• Accurate intraocular lens (IOL) power calculation is vital for successful refractive outcomes after cataract surgery.
• Traditional optical formulas are increasingly supplemented by advanced computational methods and online calculators.

Purpose of the Study:

• To review the principles behind artificial lens calculation.
• To update on recent study findings regarding novel IOL calculation approaches.

Main Methods:

• Utilizing optical biometry for computational basis of various formulas (theoretical, ray tracing, AI-based).
• Evaluating performance of newer formulas (Kane, EVO 2.0, Castrop, PEARL-DGS, OKULIX) and established ones (Barrett Universal II).
• Considering advancements like manufacturer IOL data, improved axial length measurement, and thick cornea models.

Main Results:

• Newer formulas and software demonstrate consistently good results, achieving ~80% accuracy within 0.50 D in selected populations.
• Barrett Universal II performs well in normal and long eyes but may require reconsideration for short eyes.
• Second Eye Refinement can be beneficial for short eyes with classic formulas.

Conclusions:

• Modern IOL calculation methods, including optical biometry and advanced formulas, significantly enhance refractive predictability.
• Specific formulas show superior performance in different axial length ranges, necessitating tailored selection.
• Continued refinement in measurement and calculation techniques promises further improvements in patient outcomes.