Laboratory Evaluation of the Influence of Decentration and Pupil Size on the Optical Performance of a Monofocal, Bifocal, and Trifocal Intraocular Lens

Abstract

Purpose: To assess the influence of decentration and aperture size on the optical quality of different intraocular lenses (IOLs) of the same material, body design, and refractive power using standardized optical bench testing.

Methods: Using an optical bench set-up, an aspheric monofocal (CT ASPHINA 409M; Carl Zeiss Meditec, Jena, Germany), an aspheric diffractive bifocal (AT LISA 809M; Carl Zeiss Meditec), and an aspheric diffractive trifocal (AT LISA 839M; Carl Zeiss Meditec) intraocular lens (IOL) were evaluated, each with the same distance power, body design, and material. Modulation transfer function (MTF) values were measured at spatial frequencies of 50 lp/mm and aperture sizes of 3 and 4.5 mm. Each IOL was measured while centered, then decentered by 0.25, 0.5, 0.75, and 1 mm.

Results: MTF values for the monofocal IOL at far focus with 3- and 4.5-mm aperture size were 0.80/0.80 with maximum reduction to 0.77/0.73 for 1-mm decentration, respectively. Centered IOL MTFs of the bifocal and trifocal IOLs were lower for the far focus at 0.46/0.41 and 0.39/0.26, with reduction at 1-mm decentration to 0.35/0.25 and 0.25/0.18, respectively. Values for near focus of the bifocal and trifocal IOLs reduced from 0.27/0.31 and 0.19/0.18 to 0.2/0.21 and 0.12/0.13, respectively. The trifocal intermediate focus MTF reduced from 0.15/0.10 to 0.12/0.08. MTF values of all three lenses decreased significantly under all conditions with decentration of 0.5 to 0.75 mm.

Conclusions: Monofocal lenses were least negatively affected by decentration, with mean optical quality reduction of less than 10% for 1-mm decentration at physiological pupil sizes. For diffractive bifocal and trifocal lenses, optical quality at all distances was significantly reduced if decentration exceeded 0.75 mm, with intermediate focus showing the least reduction. [J Refract Surg. 2017;33(12):808-812.].