Resonance Raman measurement of macular carotenoids in a European population

Purpose: Increasing evidence has linked the Macular Pigment (MP) to the risk of age–related macular degeneration (AMD). This study quantifies the MP using Resonance Raman Spectroscopy (RRS) and compared MP levels in the young and the elderly, including those with age–related macular degeneration, in subjects from a Mediterranean area. Methods: Sixty–nine eyes from 69 subjects (age range = 25–80 years) living in the Veneto Region have been recruited for this study; 39 subjects had no retinal lesions (among these 7 were pseudo–phakic) and 30 were patients with early non–exudative AMD in the eligible eye. RRS has been obtained by illuminating the macular area for 0.25 seconds with a 1–mm spot of 488–nm, 1.0–mW argon laser light. Results: Among normal individuals the MP level shows a significant decline with age and the population’s values are best fit with an exponential curve (R2=0.39, p<0.05). We also divided this sample into 2 subgroups, one with subjects whose age was 55 years or less and the other with subjects over 55 years. In the younger subgroup the Resonance Raman Intensity (counts+SD) was 2136+789, significantly higher than the older subgroup (1231+461, p<0.0001). Pseudo–phakic subjects with no retinal signs of AMD had MP levels within normal values (1248+612). Among patients with early non–exudative AMD the Raman signal evidenced a statistically significant reduction (871+522) compared to age–matched normal individuals (p<0.011). This observation accounts for a 29% decrease of the MP among patients with early AMD. Conclusions: Normal young subjects show a wide variation of MP levels as measured by the RRS. As age increases, an exponential reduction of macular carotenoids is apparent, even without clinically evident signs of AMD. The MP is significantly lower in the patients with early non–exudative AMD, compared to age–matched controls. These data confirm other studies carried out with the RRS, even though are in contrast with other studies made with flicker photometry which suggest that MP does not change with age, even when elderly subjects with AMD are considered. This difference could be explained by the need of a good compliance for psycophysical tests, such as flicker photometry, compared to more objective measurements such as given by the Raman method. Also, by comparing the data of this study within aged normals to other studies carried out in United States, it is evident that European population has a higher amount of carotenoids as measured by Raman (p<0.0001). This supports the hypothesis that genetics, diet and environment could account for the difference of the prevalence of AMD in Europe.