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Heterochromatic Flicker Photometry (heterochromatic + flicker_photometry)
Selected AbstractsMacular pigment optical density at four retinal loci during 120 days of lutein supplementationOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2007Adam J. Wenzel Abstract Background:, Increased consumption of lutein and zeaxanthin has been shown to increase macular pigment optical density (MPOD) in some individuals. Most interventions either obtained infrequent measures of MPOD or measured MPOD at a single retinal locus. Purpose:, The aim of this study was to measure acute changes in MPOD at four retinal loci during lutein intervention. Methods:, For 120 days, three subjects consumed 30 mg of lutein and 2.7 mg of zeaxanthin supplement per day. MPOD was measured with heterochromatic flicker photometry at 20,, 30,, 60, and 120, eccentricity three or four times per week. High-performance liquid chromatography was used to measure serum carotenoid concentrations in blood samples collected at baseline and at 30-day intervals. Results:, At the two most central loci, MPOD significantly increased in all three subjects with a mean change of approximately 0.09 log units at 20, eccentricity and 0.08 log units at 30, eccentricity. MPOD significantly increased in two subjects at 60, eccentricity, and in one subject at 120, eccentricity. The increases in MPOD appeared to be linear and continued after treatment was ended. In all three subjects, log sensitivity at the reference locus decreased linearly. Serum lutein and serum zeaxanthin increased from baseline, reaching peak concentrations after 30 days of supplementation. Conclusion:, The changes in MPOD suggest that carotenoid deposition occurs linearly and may be biased towards the central retina. Further, carotenoid deposition may occur outside the central fovea in interventions with pharmacological doses of carotenoid, resulting in underestimations of psychophysical measures of MPOD. [source] Compensation for light loss due to filtering by macular pigment: relation to hue cancellationOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2007James M. Stringham Abstract Background:, A long-standing question in colour vision research is how the visual system is able to correct for the significant absorbance of short wave light by the crystalline lens and macular pigment (MP). Such compensation must be required in order to maintain colour constancy across the retina where MP levels are changing quickly and dramatically. Objective:, We studied this compensation mechanism by measuring MP spatial density profiles and hue cancellation functions across the central retina in a sample of six young healthy subjects. Method:, Yellow (Y, 575 nm)/blue (B, 440 nm) and red (R, 600 nm)/green (G, 501 nm) cancellation functions were obtained at 0, 1, 1.75, 3 and 7° eccentricity. The MP optical density at 460 nm was measured at these same eccentricities using heterochromatic flicker photometry. One subject was assessed repeatedly over a 4-month period during daily supplementation with 30 mg of lutein (L). Results:, Hue cancellation values for the Y/B system did not change across the retina (r = 0.09). In contrast, R/G sensitivity changed as a direct function of MP absorbance (r = 0.99). The Y/B values did not change in the one subject supplemented with 30 mg L daily, despite increases in MP of about 50% over 4 months. Conclusions:, Despite large variations in MP across the retina, hue cancellation values for the Y-B system across the central retina were constant. For example, one subject's MP density declined from a central peak of 0.99 to near zero at 7° (near 90% transmission difference) yet thresholds for the Y/B system were unaffected. In contrast, the G lobe of the R/G system was directly correlated with MP density. Taken together, these results confirm that the Y/B system compensates for MP density, but the R/G system does not. [source] Repeated measures of macular pigment optical density to test reproducibility of heterochromatic flicker photometryACTA OPHTHALMOLOGICA, Issue 2 2010Stefan Hagen Abstract. Purpose:, To report the reproducibility of macular pigment optical density (MPOD) values assessed with heterochromatic flicker photometry (HFP) in healthy individuals. Methods:, Twenty-four volunteers from our department underwent MPOD testing of both eyes by flicker photometry on three separate occasions. To test reproducibility of MPOD, the coefficient of variance was calculated separately for right and left eyes. In addition, we investigated MPOD averages of right and left eyes and interocular correlations (Pearson's r) at every visit. Results:, The mean MPODs at the first visit were 0.61 ± 0.24 and 0.72 ± 0.27 in right and left eyes, respectively. Mean values of 0.58 ± 0.29 and 0.60 ± 0.21 (second visit) and 0.62 ± 0.27 and 0.63 ± 0.24 (third visit) were assessed for right and left eyes, respectively. Differences of the mean values between eyes were not significant. Correlations were weak at visits one and two (r = 0.49, p < 0.014 and r = 0.43, p < 0.038, respectively) and moderate at visit three (r = 0.58, p < 0.003). The coefficients of variance were 36.1% and 23% for right and left eyes, respectively. Conclusion:, Our mean MPODs are higher and the interocular correlations weaker compared to the literature. The coefficient of variance in both eyes is high and does not imply good reproducibility of obtained MPOD values. [source] | ||||||||||