Impact of Primary Calcification in Segmented Refractive Bifocal Intraocular Lenses on Optical Performance Including Straylight

Abstract

Purpose: To describe and analyze the impact of calcification on the optical quality of segmented refractive bifocal intraocular lenses (IOLs).

Methods: Eight segmented refractive bifocal IOLs made of hydrophilic acrylic were explanted from 8 patients due to opacification (and one opacified IOL that was not explanted) and analyzed in a cross-sectional study with laboratory analysis. Nine cases comprised three IOL models: LS-313 MF30 (5 cases), LS-312 MF30 (3 cases), and LS-313 MF15 (1 case). Material analysis with scanning and transmission electron microscopy confirmed IOL calcification. Measurements of modulation transfer function (MTF) and straylight permitted assessment of the IOL optical quality. Values were compared to a control lens.

Results: Except for one case of Nd:YAG (neodymium:yttrium-aluminum-garnet) capsulotomy, there was no secondary surgical procedure in the patients' histories. Eight of nine patients reported deteriorated visual quality, ultimately requiring IOL exchange. Material evaluation revealed fine granules of a calcium phosphate. Despite calcification, all but one lens still showed two distinct foci on the MTF measurements. Straylight values were higher than in a cataractous lens (33.1 deg²/sr) in all cases, with an average value of 170.1 ± 71.5 deg²/sr.

Conclusions: Optical quality assessment showed that IOL calcification had a small effect on the MTF of segmented refractive bifocal lenses but a large impact on the straylight levels. Accordingly, in the clinical case, straylight levels were elevated. [J Refract Surg. 2020;36(1):20-27.].