Corneal multifocality after penetrating keratoplasty or deep anterior lamellar keratoplasty is associated with intraocular lens power calculation error.

Abstract

The purpose of this study is to investigate the accuracy of intraocular lens (IOL) power calculation after penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK) and to identify the causes of predictive errors (PEs) in relation to the subjective keratometric (K) value (SK) in eyes with corneal multifocality. This retrospective study included 74 eyes that underwent cataract surgery after PK or DALK. PEs were compared between SRK/T, Haigis, Barrett Universal II (BUII) and Kane formulas. In 27 eyes with postoperative anterior segment optical coherence tomography (AS-OCT) data, SKs were calculated based on postoperative refraction, IOL position, IOL power and axial length using Zemax. This was compared with K values obtained using AS-OCT. Mean absolute PE was 1.50±1.60 dioptre in SRK/T, 1.96±1.80 in Haigis, 1.84±1.71 in BUII and 1.83±1.86 in Kane. SK was significantly correlated with true K (TK) (r=0.86, p<0.001). The difference between SK and TK showed a significant correlation with PE in SRK/T (r=0.53, p=0.001). The PE in SRK/T was modelled as a function of the change in preoperative and postoperative K values as well as the difference between TK and SK, with significant improvement in the PE after factoring in these parameters. Multifocal corneas, such as those after PK or DALK, may have SK values that differ significantly from K values obtained from AS-OCT. Therefore, traditional IOL formulas that use standard K values may lead to a refractive surprise after cataract surgery.