Abstract
Purpose: :
Schültze (1866) proposed that macular pigment (MP) serves to improve acuity by reducing the deleterious effects of chromatic aberration. In a recent study by Mengles et al (2007), the hypothesis was tested using resolution (gap) acuity and hyperacuity tasks. The results of this study indicated that there is no relation between MP and acuity as assessed with those specific conditions. Those previous tasks, however, only tested the highest spatial frequencies of the contrast sensitivity function (CSF) leaving the possibility that MP might be related to other components of the larger CSF. The present study was designed to assess the complete CSF using spectral conditions that are influenced by MP (broad-band white light) and are not (yellow light produced by a step filter).
Methods: :
MPOD will be measured using HFP. The CSF will be evaluated using sinusoidal gratings presented at six spatial frequencies (2.0, 4.0, 8.3, 16.2, 19.8, and 39.6 cycles/degree) using light produced by a 1000-W xenon-arc lamp and light of equal luminance rendered yellow using a Corning filter. A criterion-free forced choice method will be used to measure CSF thresholds.
Results: :
As noted, our initial empirical data suggest that MP is not related to the high-frequency components of the CSF.
Conclusions: :
Careful modeling of the Acuity Hypothesis suggests that no or little improvement should be expected. This hypothesis, however, is still frequently cited and has a long history. Thus, we are empirically evaluating the entirety of the CSF under carefully controlled optical conditions (results to be presented) in order to definitively determine whether MP influences contrast sensitivity based on reducing the effects of chromatic aberration.
Keywords: macular pigment • optical properties • contrast sensitivity