Comparison of Heterochromatic Flicker Photometry and Fundus Autofluorescence as Methods of Measuring Levels of Macular Pigment in vivo

Abstract

Abstract: : Purpose:Evidence suggests that macular pigment (MP) has a protective role in the development of age related macular degeneration and different methods have been used to measure the levels of MP in vivo. The purpose of this study was to examine the correlation between a psychophysical method (Heterochromatic Flicker Photometry) and a quantitative method using fundus autofluorescence (FAF). Methods: 240 healthy volunteers, aged between 17 and 50 (mean age 39.5, SD 8.03) were recruited. A comprehensive ocular history and examination was performed on all subjects. Macular pigment optical density (MPOD) was initially determined using heterochromatic flicker photometry (HFP). Following the HFP test, subjects’ pupils were dilated with 1% tropicamide and FAF images were acquired at 488 nm and 514 nm, using a modified Heidelberg Retinal Angiograph (HRA). FAF MPOD values were calculated from MPOD maps, within 1 degree around the foveal centre. MPOD for each subject was calculated as the mean MPOD for the two eyes. MPOD values calculated from the HFP method and FAF method were compared and the degree of correlation examined. Results: MPOD values of subjects’ right and left eyes were highly correlated using both HFP and FAF methods (intraclass correlation coefficients: 0.76 and 0.96 respectively). Mean MPOD using HFP was 0.43 (SD 0.20). Mean MPOD measured using FAF was 0.28 (SD 0.10). MPOD values derived from HFP and FAF methods were significantly correlated, with an intraclass correlation coefficient of 0.35 (p<0.001). Conclusions: MPOD values derived from heterochromatic flicker photometry and fundus autofluorescence were significantly correlated. Further research is required to explain the variation in values derived from the 2 methods.

Keywords: macular pigment • age-related macular degeneration • nutritional factors