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DM Snodderly, JA Mares-Perlman, BR Wooten, L Oxton, M GruberCAREDS Macular Pigment Study Group; Carotenoids and Age-Related Eye Disease: Evaluation of a Method for Measurement of Macular Pigment in Large Samples of Older Subjects . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4394.
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Purpose: To develop and evaluate a standard procedure for measurement of macular pigment density (MPOD) and spatial distribution for use in large studies of carotenoids and eye health. Methods: MPOD was measured by heterochromatic flicker photometry using a small stimulus system (Wooten et al, IOVS 40: 2481) suitable for use by support staff at multiple study sites. Fifty four women over age 50y were tested. 16 of the subjects had one or more self-reported eye diseases (mostly cataract, n = 12). The standard protocol included the following: 1) An instructional video introducing the task. 2) A measurement of critical flicker frequency to assist choice of the test frequency. 3) Measurement of MPOD at 460 nm at 4 eccentricities in the right eye relative to a baseline at 7 deg. 4) Measurement of MPOD at 2 eccentricities in the left eye. 5) Use of an additional wavelength (∼490 nm) as a check for consistency (subset of subjects). In a second session 1 to 20 days later, 48 subjects were retested in both eyes. Results: MPOD test-retest correlations in the right eye were high for both the single point at 0.5 deg eccentricity (r = 0.91) and a measure of area under the MP profile (r = 0.88). Right eye-Left eye correlations were high as well (r ∼ 0.8). In 89% of 28 subjects tested, the ratio of density at 460:490 nm was consistent with a valid measurement of retinal xanthophylls. Conclusion: Heterochromatic flicker photometry can be used with a standardized protocol to measure MPOD in representative samples of older adults. Its main limitation is the time necessary to conduct the measurements. A shorter protocol may be developed to reduce the testing time.
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