The Effect of a Yellow Filter on Visual Performance and Its Relationship With Macular Pigment Optical Density

Abstract

Purpose: : Macular pigment (MP) filters short-wave light, counteracting the deleterious effects on foveolar resolution of chromatic aberration and scattering in the ocular media.Large individual differences in MP might also be expected to lead to variations in visual function and forward light scatter. The latter can produce disability glare and reduce contrast in the retinal image. These effects become even more important at lower light levels in the mesopic range. To increase the filtering properties of the eye, especially in subjects with low MP density, we can use a yellow filter that absorbs the amount of blue light striking the retina. This study was performed a) to assess the effect of a yellow filter on mesopic visual function and light scattering and b) to relate variations in these two factors provoked by the yellow filter to MP density levels in young subjects.

Methods: : Measurements were obtained from 40 healthy young subjects aged 23.3 ± 3.0 years. The optical density of the MP was estimated at the fovea using the Metropsis Test (Cambridge Research System), which is based on the apparent motion photometry method and employs a CRT monitor for stimulus presentation. Visual acuity, contrast sensitivity and scattered light were measured in the right eye with and without a yellow filter under mesopic luminance conditions (0.1 to 0.2 cd/m²). Visual acuity (logMAR in steps of 0.02 log units) was measured using high-contrast (96%) and low-contrast (5%) logMAR letter charts. Contrast sensitivity was determined using the Pelli-Robson chart. Scattered light on the retina was measured using a computerized straylight meter (C-Quant, Oculus) according to the psychophysical compensation comparison method. Values are expressed as logs (of the straylight parameter) for which higher values indicate more scattered light and more sensitivity to glare.

Results: : Mean foveal MP optical density was 0.40 density units (SD 0.14; range 0.11 to 0.7). Light scattering in the eye, low-contrast visual acuity and contrast sensitivity were significantly worse, albeit slightly, with the yellow filter (Table 1). However, no correlation was detected between foveal MP density and the changes in visual acuity, contrast sensitivity and light scatter attributable to the yellow filter.

Conclusions: : The variations in mesopic visual function and light scatter produced by the yellow filter showed no correlation with inter-subject differences in MP density in young subjects.

Keywords: macular pigment • contrast sensitivity • visual acuity