Citation: Millán MS, Vega F, Ríos-López I. Polychromatic image performance of diffractive bifocal intraocular lenses: longitudinal chromatic aberration and energy efficiency. Invest Ophthalmol Vis Sci. 2016;57:202157: -202857: . DOI:10.1167 PURPOSE. The study evaluated-theoretically and experimentally-the longitudinal chromatic aberration (LCA) and through-focus energy efficiency (TF-EE) of diffractive-refractive bifocal intraocular lenses (2f-IOLs).METHODS. Four aspheric 2f-IOLs (Tecnis þ4.00 diopter [D] ZMA00, þ2.75 D ZKB00, and AcrySof þ4.0 D SN6AD3, þ2.5 D SV25T0) of same base power 30 D, but different design, additional (add) power, and different material, were tested in vitro in terms of TF-EE when illuminated by 3 red (k R ¼ 625 nm), green (k G ¼ 530 nm), and blue (k B ¼ 455 nm) lights. The LCA affecting the distance and near foci was derived theoretically and measured experimentally from the contributions of the IOLs' refractive and diffractive powers. Longitudinal chromatic aberration was evaluated in a pseudophakic schematic eye.
RESULTS.The distance focus of all 2f-IOLs showed lower energy efficiency (EE) for the blue than for the red light. AcrySof IOLs showed the largest amount of positive LCA in the distance focus that, combined with corneal LCA, would increase the resulting distance LCA in a pseudophakic eye. The near focus of all 2f-IOLs showed higher EE for the blue than for the red light. Better compensation for the LCA of a pseudophakic eye at near focus is obtained with Tecnis than with AcrySof 2f-IOLs.CONCLUSIONS. The energy distribution between the foci of diffractive 2f-IOLs depends on the lens design, the illumination wavelength, and to a lesser extent, the add power. In distance vision, 2f-IOLs' refractive base power increases the positive LCA of prior ocular media, and the resulting LCA may even surpass the natural LCA of human eye. In near vision, however, the achromatizing effect of diffractive 2f-IOLs may compensate, in part, the natural eye's LCA.
SummaryAn increasing demand of spectacle independence after cataract surgery or clear lens extraction has greatly stimulated the development of multifocal intraocular lenses (MIOLs). Optical design has played an essential role in this progress. Based on the principle of simultaneous vision, MIOLs overcome the loss of accommodation by providing at least two primary powers intended for distance and near vision. Diffraction‐based MIOLs have proved better optical performance than multizonal refractive MIOLs and accommodative IOLs. Some new designs of diffractive MIOLs attempt to direct light either to an intermediate focus location or to an extended focal segment for an improved visual acuity at intermediate distances. Although the patient primarily perceives the focused image, they can also experience disturbing visual phenomena, such as halos and glare. The optical imaging performance of MIOLs, as referred to some quality metrics, is assessed using in‐vitro as well as in‐vivo testing methods. This work reviews the objective imaging quality of a variety of MIOLs measured in an optical bench and compares the experimental results with those obtained in the clinical practice.
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