Spectral absorbance and spatial distribution of macular pigment using heterochromatic flicker photometry

Purpose. The validity of the heterochromatic flicker photometric (HFP) technique for measuring macular pigment (MP) was assessed by evaluating the spatial density and spectral absorption curves of normal subjects. Methods. Standard Maxwellian view optics were used to measure MP spatial density and spectral absorption curves. Four subjects with normal color vision and one protanope were tested. All of the subjects were experienced psychophysical observers. Results. Spatial density profiles for all subjects were nearly symmetric. The width of the spatial distribution, at half maximal density, averaged 0.70 degrees (standard deviation = 0.15). A first-order exponential decay with eccentricity described the distribution profile well (average r(2) = 0.95). The shape of the spectral absorption curves matched an ex vivo template closely at wavelengths greater than approximately 430 nm. Stimulus size did not influence the derived spectral curves. Conclusion. Based on data from this study and others, the HFP method appears to be a valid method for measuring MP density in subjects without retinal disease.