Color Differences in Violet- and Blue-Blocking IOLs

Abstract

Purpose:: Some new intraocular lenses (IOLs) block ultraviolet (UV) radiation and either violet light or violet and blue light. Differences have been reported in anomaloscope and cone-specific contrast sensitivity tests and a case report has documented explantation of a blue-blocking IOL for color disparity problems. This study is a colorimetric analysis of how visible light blocking IOLs potentially affect color difference discrimination.

Methods:: Standard illuminants, IOL transmittance spectra, and CIE color matching functions were used to compute tristimulus values and chromaticity coordinates for light transmitted by visible-light blocking and UV-only blocking IOLs. The spectra of the absorbed light were analyzed similarly. Several color difference formulae were evaluated for pairs of IOLs and compared to criteria for color discrimination. Adjustments were made to investigate the effects of intensity and some artificial light sources.

Results:: Transmitted light through the visible light blocking IOL has yellow or orange chromaticity coordinates on a standard CIE chromaticity diagram. Transformations to more perceptually-uniform color spaces yield coordinate differences between pairs of transmitted spectra that are 6 times higher than typically perceptible thresholds. These could be considered acceptable color matches, so this level of color difference may not be demonstrable with standard clinical color vision tests. Calculations show greater differences for pairs of the complementary colors in hues of violet and blue. Specifically for the blocked-light spectra, the coordinate differences between IOL pairs are at least 2 times greater than color differences for transmitted light, and possibly much higher depending on the simulated illuminants.

Conclusions:: Colors transmitted by IOLs can appear similar for high-pass chromophores with either gradual or sharp cut-offs in spectral transmittance. Standard color vision testing methods do not detect the color differences, and most individuals readily adjust to vision with visible light blocking IOLs. Colorimetric analysis provides insight into the colors blocked by different spectral filters, and determined that color discrimination is possible. These tools could improve color vision tests and IOL evaluations.

Keywords: color vision • intraocular lens • color appearance/constancy