Macular Pigment Quantification with Multispectral Retinal Image Analysis

Objective: Variations in macular pigment (MP) have been linked with changes in the risk of visual loss secondary to macular pathology. MP density can be modified by diet; however there doesn’t appear to be a direct link between dietary intake of MP components and MP density in the retina and clinicians therefore need a reliable and objective method for MP measurement to establish if any intervention is yielding the required results. The objective of this study was to investigate whether multispectral retinal image analysis (MRIA), a new technique for mapping retinal pigments, is useful for measuring levels and distribution of MP to find differences between individuals with no clinical evidence of macular pathology and those diagnosed with Age-related Macular Degeneration (AMD). Methods: The study involved 90 volunteers from three subject groups: aged under 50 without AMD, aged 50 and over without AMD and aged 50 and over with AMD. The experiments yielded 607 usable data sets that were used for analysis. Multispectral image data was acquired at six selected wavelengths using a modified fundus camera. MRIA maps of MP were computed from 3 × 3 mm regions of interest (approximately 10 degrees of visual angle) centred at the fovea. Indices characterising MP distribution were computed both for individuals and for the three subject groups. For comparison Macular Pigment Optical Density (MPOD) measurements were acquired from the Macular Pigment Screener 9000 (MPS) based on the heterochromatic flicker photometry (HFP). Correlations for MP quantities measured with the two methods were computed between MP quantity and age, MP quantity and AMD diagnosis, and between the two methods. Results: MP maps obtained from MRIA were consistent with known histology and in agreement with expectations based on previous studies. Pooled results from the three groups suggest that the overall levels of MP across both the fovea and the parafovea are on average higher in healthy under-50 individuals than that over-50 with or without AMD. MP distribution might be more irregular in the over-50 groups than in the younger group. The correlation between age and MP levels was weak as measured individually by both techniques. The MRIA indices were not correlated with HFP-MPOD measurements for individuals, but high correlation was found between mean HFP-MPOD and mean MRIA peak value for pooled results. Conclusion: MRIA has potential to offer an objective, fast and reliable method of measuring MP throughout the posterior pole.