In vivo Evidence for Reduced Autofluorescence Efficiency at the Fovea: Implications for Assessment of Macular Pigment

Abstract

Abstract: : Purpose: To optimise optical density measurements of macular pigment made by fundus autofluorescence by comparison with those made by motion photometry. Methods: Fundus autofluorescence images were obtained through a high-pass barrier filter (1 x10^-5 transmission at 495nm) using a modified scanning laser ophthalmoscope (488nm radiation). Optical density values were derived from fundus autofluorescence images at 12 retinal locations between 0 and 7 degrees relative to values at 7 degrees eccentricity. MP profiles derived from minimum motion matches were made in the same subjects and over the same retinal eccentricities. Results: Comparison of mean relative optical density values obtained using the psychophysical and imaging methods revealed a linear relationship over para-foveal areas (>1.8 degrees eccentricity) but deviation over central areas (<1.8 degrees). A second order polynomial regression provided the best fit for all data (r²=0.99). Differences between linear and polynomial regressions were used as an eccentricity-dependent correction. Conclusions: Assessment of MP optical density using fundus autofluorescence imaging requires the introduction of an eccentricity-dependent correction due to reduced autofluorescence efficiency at the fovea.

Keywords: macular pigment • age-related macular degeneration • image processing