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I.F. Leung, S. Caldarella, D.M. Snodderly; The Repeatability of Macular Pigment Measurement Using Flicker Photometry . Invest. Ophthalmol. Vis. Sci. 2003;44(13):406.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:: To determine the reliability of macular pigment optical density (MPOD) measured across the foveal region of normal older subjects in multiple measurements. Methods:Twenty five healthy subjects (age: 67 ± 6, mean ± SD) were recruited for psychophysical measurement of macular pigment optical density by a free viewing flicker photometer. The test light at 460 nm (blue, maximal absorption by macular pigment) and 550 nm (green, no absorption by macular pigment) were compared and adjusted in luminance until no flicker perceived. The profile of the pigment density was measured by circular or ring targets with radii of 0.25, 0.5, 1 and 1.75 degrees . The reference point was located 7 degrees from fixation. The measurement was repeated (except for two subjects with 3 repeated measurements) on 4 different days for each individual. The total luminance of the targets were kept constant when the luminance of the blue and green varied. Results:Standard deviation of the MPOD decreased significantly from first to last visit (P< 0.05). However, the mean MPOD of the population did not change significantly from visit to visit (P > 0.1). Forty percentage of the subjects had within-subject variance ≥ between-subject variance when all 4 visits were included for statistical analysis. This value decreased to 4% when the data from the first visit was eliminated. The mean MPOD at 0.5 degree eccentricity was 0.50 ± 0.18 (Mean ± SD). A second peak or flattened profile were observed in 24 % of the subjects. Conclusions:The variability of this test could be reduced by repeated measurement and practice in this population. In spite of the variability of individual settings in the early tests, the mean values for each subject appear to be relatively robust.
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