Comparative Analysis of Twenty Intraocular Lens Power Calculation Formulas in Medium-Long Eyes

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optics

Background:

• Accurate intraocular lens (IOL) power calculation is crucial for refractive outcomes after cataract surgery.
• Formula selection for IOL power calculation is often dependent on ocular axial length.
• Medium-long eyes present unique challenges for IOL power calculation accuracy.

Purpose of the Study:

• To compare the predictive accuracy of twenty different IOL power calculation formulas.
• To evaluate formula performance specifically in eyes with medium-long axial lengths (24.50-25.99 mm).
• To identify the most accurate formulas for this patient cohort.

Main Methods:

• Retrospective review of 95 eyes with medium-long axial lengths undergoing uneventful phacoemulsification.
• Preoperative IOL power calculated using six standard formulas (Barrett Universal II, Haigis, Hoffer Q, Holladay 1, Holladay 2, SRK/T).
• Postoperative refraction measured, and IOL power recalculated using fourteen additional formulas, including newer AI-based options.

Main Results:

• The SRK/T formula exhibited the lowest standard deviation of prediction error (0.179) and highest percentage of eyes within ±0.50 D (98.95%).
• Holladay 1 formula also showed high accuracy, performing significantly better than most other formulas evaluated.
• Olsen (OLCR) and Castrop formulas demonstrated the lowest accuracy among the twenty tested.

Conclusions:

• The SRK/T formula is recommended as the most accurate for IOL power calculations in medium-long eyes.
• Holladay 1 formula offers comparable accuracy and is a reliable alternative.
• While performance varied, all tested formulas achieved prediction errors within ±0.50 D in over 74% of cases.