IOL Power Calculation Formulas in Post-LASIK Eyes Using Two Biometry Systems in Vietnam

Area of Science:

• Ophthalmology
• Refractive Surgery
• Biomedical Engineering

Background:

• Cataract surgery replaces the clouded lens with an intraocular lens (IOL) to restore vision.
• Precise IOL power calculation is essential for achieving desired postoperative refractive results.

Purpose of the Study:

• To compare the predictive accuracy of various IOL power calculation formulas.
• To evaluate these formulas in eyes with prior LASIK surgery.
• To assess the impact of two biometric devices (LenStar 900 and IOLMaster 500 with ultrasound) on formula accuracy.

Main Methods:

• Retrospective observational study of 37 eyes from 29 patients with prior LASIK and subsequent cataract surgery.
• Biometric data (axial length, keratometry, etc.) collected using LenStar 900 or IOLMaster 500 with ultrasound.
• IOL power calculated using Shammas PL, Haigis-L, Barrett TK no history, Shammas Cooke, and EVO 2.0 formulas.
• Mean Absolute Error (MAE) assessed at 3 months postoperatively for each formula and device.

Main Results:

• For LenStar 900, MAE ranged from 0.389 D (Barrett TK no history) to 0.574 D (Shammas Cooke).
• For IOLMaster 500 + US, MAE ranged from 0.423 D (Barrett TK no history) to 0.601 D (Shammas Cooke).
• LenStar 900 showed significantly lower MAE for Shammas PL, Shammas Cooke, and EVO 2.0 compared to IOLMaster 500 + US.

Conclusions:

• IOL power prediction accuracy in post-LASIK eyes depends on the biometry device used.
• Barrett TK (no history) and EVO formulas performed well with LenStar 900.
• Haigis-L demonstrated consistent accuracy across both devices, suggesting its reliability with non-synchronous biometry systems.