Light scattering in intraocular lenses explanted 15 to 40 years after surgery

Abstract

The optical quality of intraocular lenses (IOLs) of different materials that have been implanted from 16 to 44 years in human eyes was studied. The IOLs were explanted due to other causes than loss of transparency. The scattered light from the IOLs was assessed in two angular regimes by using dark field images (for wide angles) and the optical integration method (for narrower angles). No evident differences were found in the scattering intensities processed from the dark images. The explanted lenses presented slightly increased amounts of straylight between 1 and 5.1° when compared to a reference new unused lens.

Fig. 1.

Setup for the dark field photography. Only the scattered light is captured by the camera.

Fig. 2.

Instrument for the assessment of the straylight as function of θ for the tested IOLs. Solid ray tracing depicts the light trajectory when IOLs with positive power are tested. In the case of negative IOLs, the light is focused in the camera by incorporating the L6 lens in a conjugated plane with the IOL, as represented by the dashed tracing. The focusing for each IOL is manually adjusted by the axial displacement of the camera.

Fig. 3.

Acquired and quantified scattering from dark field photography. (a) Dark field images. (b) Mean of the scattered intensities (MSI) within the optical area of IOLs and supporting slide (without IOL). (c) MSI values as function of the time since implantation for IOLs with this information available (see Table 1). The dashed blue line depicts the linear fitting (R²=0.06).

Fig. 4.

Straylight in tested IOLs. Angular distribution of the (a) positive and (b) negative IOLs, the non-implanted Tecnis IOL, a biconvex lens (i.e., baseline) and an elderly (70 y.o.) eye according to the CIE standards. (c) Area under the straylight profiles, preserving the order from Fig. 3(b). (d) Areas, referred to the corresponding baseline value, as function of the time since implantation of the IOLs with this available data. The units of the area under the s(θ) profile are deg³/sr.