Measurement of Carotenoids in Perifovea using the Macular Pigment Reflectometer

The macular pigment reflectometer (MPR) objectively measures the overall macular pigment optical density (MPOD) and further provides the lutein optical density (L-OD) and zeaxanthin optical density (Z-OD) in the central 1 degree of the fovea. A modification of the technique was developed to evaluate in vivo carotenoid density eccentric to the fovea. An adjustable track system with red LED lights was placed 6.1 m away from the participant to facilitate ocular fixation. Lights were spaced appropriately to create increments of 1 degree retinal disparity during the reflectometry measurements. All reflectometry measurements were obtained with pupillary dilation. The mean MPR-MPOD value for the central measurement was 0.593 (SD 0.161) with an L-OD to Z-OD ratio of 1:2.61. The MPR-MPOD value at 1 degree was 0.248 and the mean MPR-MPOD value at 2 degrees in the parafoveal region was 0.143. The L-OD to Z-OD ratio at 1 degree and 2 degrees off center was 1.38:1.0 and 2.08:1.0, respectively. The results demonstrate that MPOD measurements obtained using the MPR decrease as a function of retinal eccentricity and that there is a higher concentration of zeaxanthin centrally compared to lutein. The L-OD to Z-OD ratio changes with foveal eccentricity, with twice more lutein than zeaxanthin at 2 degrees off center. Our technique successfully provides a quick in vivo method for the measurement of macular pigment optical density at various foveal eccentricities. The results agree with prior published in vivo and in vitro xanthophyll carotenoid density distribution measurements.