Third- and fourth-generation formulas for intraocular lens power calculation before and after phakic intraocular lens...

To determine the effect of Visian Implantable Collamer Lens phakic intraocular lens (pIOL) insertion on biometric parameters and IOL power calculation.

Beirut Eye and ENT Specialist Hospital, Beirut, Lebanon.

Prospective case series.

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).

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.

Phakic IOL insertion did not affect IOL power calculation. If preoperative data are not available, postoperative values can be used in IOL calculation formulas.