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EA Ponce, J Nieto, R Rosen, J Garcia, P Garcia, R Gentile; Macular Pigment Density Determination: Heterochromatic Flicker Photometry and Scanning Laser Reflectometry . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2573.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare the Heterochromatic Flicker Photometry (HFP) and Scanning Laser Reflectometry (SLR) techniques of Macular Pigment Density (MPD) determination. Methods: The study included 7 normal eyes (6 patients). MPD was first determined at 10 min, 30 min, 1deg and 2deg eccentricity with HFP. After dilating with Tropicamide 1%, patients were dark-adapted for 15 min. Digital images were acquired using a Scanning Laser Ophthalmoscope (RodenstockR SLO 101 model 680 462) using separate Argon green (514 nm), and Argon blue (488 nm) wavelengths. Photoreceptor photopigment was bleached for 2 min. Images were aligned and averaged using Photoshop 5.5R, then converted to tables representing their 8-bit greyscale numeric values with Impuls-Imaging Vision XXLR v 2.01, and MPD was calculated in Microsoft ExcelR. Mean MPD was determined in concentric 3-pixel, 10 min wide rings, centered on the peak of the distribution. Results: Mean MPD with HFP and SLR were 0.51 and 0.40 at 10 min (SD 0.06), 0.43 and 0.32 at 30 min (SD 0.04), 0.29 and 0.22 at 1deg (SD 0.03), and 0.07 and 0.09 at 2deg (SD 0.02) respectively. There was minimal variation in mean MPD differences, with the differences being 0.11 for 10min (p < 0.19), 0.11 for 30 min (p < 0.11), 0.07 for 1deg(p < 0.11) and -0.02 for 2deg (p < 0.40). Conclusion: SLR yielded a lower mean MPD when compared to HFP. The differences between methods were consistent within the central two loci that might suggest an offset factor may be needed to compare the methods to each other. Larger numbers of subjects should reveal if this relationship is accurate.
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