Lutein and zeaxanthin measured separately in the living human retina with fundus reflectometry

To separately measure the optical densities of lutein (L) and zeaxanthin (Z) in the human retina in vivo. L and Z are the basic constituents of the macular pigment (MP).

Spectral fundus reflectance was measured in 23 subjects (group 1) at 0 degrees , 1 degrees , 2 degrees , 4 degrees , and 8 degrees eccentricity with a modified macular pigment reflectometer. A model generated the optical densities of L (LOD) and Z (ZOD), using their slightly different absorption spectra. Three other subjects (group 2) took 20 mg/d zeaxanthin for 6 months; they were measured approximately monthly for 18 months.

Mean LOD for group 1 at the central fovea was 0.200 +/- 0.061 (range, 0.085-0.305), mean ZOD was 0.494 +/- 0.169 (range, 0.169-0.806), resulting in a mean Z fraction [ZOD/(LOD + ZOD)] of 0.71. ZOD dropped faster toward the periphery than LOD, measuring 0.044 and 0.010 (Z fraction 0.18) at 8 degrees , respectively. Zeaxanthin supplementation in group 2 caused a significant increase in ZOD, and no or minor changes in LOD. ZOD further increased over a 10-month period after supplementation in all subjects.

LOD and ZOD had different spatial profiles that, apart from scaling factors, showed similarity to in vitro literature data. Supplementation with Z caused LOD to decrease and ZOD to increase. These results strongly suggest that the optical densities of L and Z can be assessed in vivo by fundus reflectometry, opening new ways of investigating the putative protective roles of L and Z in retinal disease.