Comparative accuracy of Barrett true-K and Haigis-L formulas for intraocular lens power calculation in post-laser-assisted <i>in situ</i> keratomileusis cataract surgery

Objectives: The objective of the study is to compare the refractive accuracy of the Barrett true-K total keratometry (TK) and Haigis-L intraocular lens (IOLs) power calculation formulas in post-laser-assisted in situ keratomileusis (LASIK) eyes undergoing cataract surgery. Materials and Methods: This retrospective comparative study included 60 eyes of 40 patients with a history of LASIK who underwent uneventful phacoemulsification with monofocal IOL implantation at a tertiary eye care centre in Gujarat, India (2024–2025). IOL power was calculated using Barrett True-K TK in 30 eyes (Group 1) and Haigis-L in 30 eyes (Group 2). The cohort comprised 44 myopic LASIK eyes (73.3%) and 16 hyperopic LASIK eyes (26.7%). Outcome measures included post-operative uncorrected distance visual acuity (UDVA), best-corrected visual acuity (BCVA), spherical equivalent (SE), mean absolute error (MAE), prediction error (PE) and residual astigmatism. PE was defined as achieved minus predicted post-operative SE. Statistical analysis included paired and independent t -tests or non-parametric equivalents, Chi-square tests for categorical variables and age-adjusted analysis of covariance with generalised estimating equations to account for baseline age differences and inter-eye correlation. Results: Both formulas produced significant post-operative improvement in UDVA and BCVA (all P &lt; 0.001). At 1 month, UDVA was significantly better with Barrett true-K TK (0.04 ± 0.08 logMAR) compared with Haigis-L (0.12 ± 0.19 logMAR; P = 0.021), while BCVA was comparable between groups (0.01 ± 0.03 logMAR; P = 0.82). Mean post-operative SE was closer to emmetropia with Barrett true-K TK (−0.29 ± 0.34 D) than with Haigis-L (−0.44 ± 0.54 D). Barrett True-K TK demonstrated significantly lower MAE (0.34 ± 0.12 D) compared with Haigis-L (0.54 ± 0.21 D; P = 0.038) and a higher proportion of eyes within ±0.50 D of target refraction (80% vs. 63%). Subgroup analysis showed consistently lower MAE with Barrett true-K TK across axial length categories and LASIK types, with greater variability observed in post-hyperopic LASIK eyes. Conclusion: Both formulas yielded satisfactory outcomes in post-LASIK cataract patients; however, Barrett true-K TK demonstrated superior refractive predictability and accuracy. Its independence from historical refractive data supports its use as the preferred IOL calculation formula in post-refractive eyes.