Third- and fourth-generation formulas for intraocular lens power calculation before and after phakic intraocular lens insertion in high myopia

Purpose: To determine the effect of Visian Implantable Collamer Lens phakic intraocular lens (pIOL) insertion on biometric parameters and IOL power calculation. Setting: Beirut Eye and ENT Specialist Hospital, Beirut, Lebanon. Design: Prospective case series. Methods: The IOLMaster 500 biometer was used to measure axial length (AL), keratometry (K), and anterior chamber depth (ACD) values before and 2 months after pIOL implantation. The IOL power was calculated using third-generation formulas (SRK/T, Holladay 1, Hoffer Q) and fourth-generation formulas (Haigis, Barrett Universal II). Results: The study comprised 24 eyes (12 patients). The preoperative and postoperative AL were comparable (27.35 mm ± 1.51 [SD] versus 27.36 ± 1.6 mm; P =.91), as were the K values. There was a significant difference between the preoperative and postoperative ACD (3.67 ± 0.46 mm versus 3.4 ± 0.56 mm; P =.008). The mean IOL power calculation did not change significantly using the Haigis (10.04 ± 3.42 diopters [D] versus 10.1 ± 3.59 D; P =.69), SRK/T (9.85 ± 3.41 D versus 9.94 ± 3.58 D; P =.44), Holladay 1 (9.70 ± 3.47 D versus 9.80 ± 3.64 D; P =.45), Hoffer Q (9.70 ± 3.40 D versus 9.85 ± 3.59 D; P =.37), or Barrett Universal II (9.29 ± 3.52 D versus 9.35 ± 3.71 D; P =.63) formula. Conclusions: Phakic IOL insertion did not affect IOL power calculation. If preoperative data are not available, postoperative values can be used in IOL calculation formulas.