Intraocular lens power calculation after excimer laser corneal refractive surgery: A retrospective study to compare the predictability and the efficacy of commonly used and modified formulas.

Purpose: Our article aims to assess the accuracy of modified and commonly used formulas of intraocular lens (IOL) power calculation after excimer laser corneal refractive surgery.

Methods: This is a retrospective study, with data retrieved for 50 eyes of 32 patients who underwent uncomplicated cataract surgery after excimer laser corneal refractive surgery. The expected spherical equivalent was calculated using the American Society of Cataract and Refractive Surgeons (ASCRS) IOL power calculator for Shammas and Barrett True-K, using three-fourth generation formulas (Haigis-L, Barrett True-K no history, and Holladay 2), and using three-third generation formulas (SRKT, Holladay 1, and Hoffer Q) with single k, as a reference, and adjusting these formulas by calculating the keratometry readings by two methods (Jarade's index and formula). The mean refractive error and mean absolute refractive error (MARE) were calculated at the 1 postoperative month.

Results: When all data was available (eight eyes), 13 formulas were compared. Holladay 1 as modified by Jarade's index and formula, and Hoffer Q as modified by Jarade's formula resulted in MARE <0.75D ( < 0.05). In the group of 25 eyes with only ablation available, the formulas with MARE <0.75D were Haigis L, Barrett TK (from ASCRS), Hoffer Q, and the three conventional formulas in Jarade's index ( < 0.001). In the group of 17 eyes with no available prerefractive data, only Haigis-L and Barret TK (no history) had a MARE <0.75 D.

Conclusion: The use of Hoffer Q or Holladay 1, when prerefractive data are available, gives reliable results with Jarade's index.