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Considerations on the Haigis formula: Are better outcomes possible with tuning?
Achim Langenbucher1, Nóra Szentmáry2,3, Jascha Wendelstein1,4
1Department of Experimental Ophthalmology, Saarland University, Homburg, Saar, Germany.
Acta Ophthalmologica
|March 29, 2025
Summary
This study enhanced the Haigis formula for intraocular lens (IOL) power calculation, achieving clinically relevant improvements in refractive prediction accuracy. Further prospective studies are needed to confirm these benefits in a larger patient population.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Optical Engineering
Background:
- The Haigis formula is a widely used method for intraocular lens (IOL) power calculation.
- Optimizing IOL power prediction is crucial for achieving desired refractive outcomes after cataract surgery.
- Existing formulas may have limitations in accuracy across diverse patient populations and lens types.
Purpose of the Study:
- To develop a vergence-based IOL power formula by modifying the classical Haigis formula.
- To improve refractive prediction accuracy while maintaining the original formula's architectural integrity.
- To assess the performance of new formula variants using real-world biometric data.
Main Methods:
- Four novel formula variants (A-D) were designed, incorporating adjustments for axial length and corneal radii.
- Specific variants included modifications to the keratometer index and an additional term for effective lens position.
- Formula constants and keratometer indices were optimized using nonlinear iterative techniques to minimize root mean squared prediction error (RMSPE).
- Performance was evaluated using four datasets of biometric data from eyes implanted with different IOL models.
Main Results:
- All four developed formula variants demonstrated a reduction in RMSPE compared to the original Haigis formula, with improvements ranging from 2.8% to 12.6%.
- Variants B and D, which included an additional constant (a3) for lens thickness, outperformed variants A and C.
- Variants C and D, featuring an adjusted keratometer index, showed slightly better performance than variants A and B, respectively, across all datasets.
Conclusions:
- The modified Haigis formula variants show promising reductions in refractive prediction error, suggesting potential clinical relevance.
- The observed improvements in RMSPE warrant further investigation.
- Prospective, multicenter studies with large sample sizes are recommended to validate the clinical benefits of these enhanced formulas.
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