Abstract
Purpose::
Standard (UV-blocking) intraocular lenses (IOLs) transmit more blue light than the normal adult lens. The increased blue light is a possible a risk factor for macular degeneration. Blue-blocking IOLs (BBIOLs) were developed to decrease blue light exposure and reduce this risk. While the BBIOL has no reported effect on color vision measured by FM 100 Hue and D15, color-related problems can occur in patients with a standard IOL in one eye and the BBIOL in the other. Our purpose was to determine if the BBIOL impacts color vision on a range of tests including those which isolate cone-specific mechanisms.
Methods::
Color vision was assessed in 23 visually-normal phakic adults in a repeated-measures design across three test conditions: YF (yellow filter with color & luminance transmittance of BBIOL), GF (luminance-matched grey filter), and NF (no-filter baseline). Tests included: PIP plates (Dvorine, SPP2, SPP3), Rayleigh and Moreland anomaloscope, Farnsworth lantern, Lanthony desaturated D15, FM 100 Hue, and cone specific contrast sensitivity (CCS). Four pseudophakes with standard IOLs and two color deficient observers were also tested.
Results::
There was no significant difference in performance across the three conditions (YF, GF, NF) on PIP, lantern or on FM 100 hue (total error, RG, BY; p=0.9). Yet separate analysis of FM 100 hue box 3 (blue hues) showed a trend for increased error for YF (p<0.07), and the desaturated D15 confusion index for YF was significantly elevated (p<0.03). The Moreland anomaloscope match, specific to the blue (S) cone system, was significantly shifted toward blue (tritan) for YF (p<0.0001), and CCS revealed a selective and significant decrease in S cone CS for YF. Pseudophakes with standard IOLs and color deficient observers showed similar tritan effects when tested with YF. In contrast to these selective tritan defects, there was no difference between YF, GF and NF on the Rayleigh (red-green) anomaloscope or on red and green cone CS.
Conclusions::
A yellow filter with color and luminance transmittance of the BBIOL induces a tritan color defect on the Moreland anomaloscope and S cone CS; with increased errors on the desaturated D15 and box 3 of the FM 100 hue test. The tritan effect, observed in color normal (phakic) subjects, pseudo-phakes (standard IOLs), and in red and green color deficiency, is due to a selective decrease in stimulation of S cones. Compared to the adult lens, the YF chromophore decreases retinal illumination between 430-460 nm (hence the tritan defect) but increases illumination between 400-425 nm, perhaps confounding a blue-light protective effect.
Keywords: color vision • intraocular lens • contrast sensitivity