On the longitudinal chromatic aberration of the intraocular lenses

Primary properties of the optical materials used for intraocular lenses (IOLs) are biocompatibility and stability over time after implantation. Additionally, modern IOLs need to be flexible to be implanted through a small incision. Several compounds are usually added to existing materials (such as acrylic) to enhance the above-mentioned properties. Moreover, UV-absorbing substances are added in the IOL materials to mimic the spectral transmittance of the natural lens. Although manufacturers usually provide information for the geometry of IOLs, chromatic dispersion data are usually not available. The purpose of this study was to estimate the dispersion properties of a few materials used for IOLs.

We measured the chromatic focal shift of two common types of IOLs using a simple, optical method. From the chromatic focal shift, we calculated the dispersion properties of the materials (polymethylmethacrylate and acrylic) used for the IOLs under investigation.

The results deviate from the existing data in the literature for the corresponding pure materials.

The presence of the UV absorber in the optical material significantly affects its dispersive properties. Longitudinal chromatic aberration (LCA) of the IOLs is approximately three times higher than LCA of the natural crystalline lens. It is expected that eyes implanted with IOLs suffer from increased LCA in comparison with intact eyes. It remains to be investigated if this increase in LCA has a significant impact on visual function.