Comparison of Legacy and New No-History IOL Power Calculation Formulas in Postmyopic Laser Vision Correction Eyes

Area of Science:

• Ophthalmology
• Refractive Surgery
• Biomedical Optics

Background:

• Accurate refractive prediction is crucial for successful cataract surgery, especially in eyes with prior myopic laser vision correction (M-LVC).
• Legacy formulas often struggle with the altered corneal geometry post-M-LVC, leading to refractive surprises.
• Advancements in biometry and formula development aim to enhance predictability in these challenging eyes.

Purpose of the Study:

• To compare the refractive prediction accuracy of traditional (legacy) versus novel (new) no-history formulas in eyes previously treated with myopic laser vision correction (M-LVC).
• To evaluate the performance of different new formulas based on the inclusion of standard keratometry (K), posterior keratometry (PK), or total keratometry (TK) values.

Main Methods:

• A retrospective cohort study involving 576 eyes (400 patients) that underwent cataract surgery after M-LVC.
• Biometric measurements, including K, PK, and TK, were obtained using a swept-source OCT (SS-OCT) biometer.
• Refractive prediction errors for 11 no-history formulas (legacy and new) were calculated and compared using heteroscedastic testing, ranked by root mean square error (RMSE).

Main Results:

• New no-history formulas demonstrated superior refractive accuracy compared to legacy M-LVC formulas.
• Formulas incorporating posterior corneal power (PK/TK) showed better performance than those using K values alone.
• Among formulas using PK/TK, EVO 2.0-PK was superior to Hoffer QST-PK (P < 0.005). Among formulas using K only, Pearl DGS-K and EVO 2.0-K outperformed Hoffer QST-K and Barrett True K NH-K (all P < 0.005).

Conclusions:

• New no-history formulas are recommended over legacy formulas for post-myopic laser vision correction (M-LVC) cataract surgery.
• The top-performing formulas, including EVO 2.0-PK, Pearl DGS-PK, and Barrett True K-TK, utilized posterior corneal power data.
• For formulas relying solely on standard keratometry, EVO 2.0-K and Pearl DGS-K provided the best refractive outcomes.