Macular pigment density and quantitative fundus autofluorescence in young healthy subjects

Abstract PURPOSE: To measure macular pigment (MP) and find possible correlation between heterochromatic flicker photometry (HFP) and quantitative autofluorescence (qAF) in young healthy subjects. METHODS: We enrolled 80 eyes of 40 young healthy subjects. Macular pigment optical density (MPOD) was automatically calculated with a macular pigment screener (MPS; MPODHFP). We calculated qAF comparing gray levels (GL) of qAF images with GL of internal reference of a confocal scanning laser ophthalmoscopy. A raster of concentric rings was used to automatically calculate foveal qAF (qAFF) values (0°-1.2°); inner ring (1.3°-4.3°; qAF3); middle ring (4.5°-7°; qAF6); and outer ring (7.2°-9.7°; qAF8). The test-retest coefficient of repeatability was calculated with Bland-Altman method. The between-eyes coefficient of agreement and correlation between the two techniques were calculated. Finally, an estimation of MPOD from qAF was performed (MPOD-AF), to find possible direct correlations with MPODHFP obtained with the MPS II. RESULTS: Paired data sets of repeated measurements were not statistically different for MPS II (P = 0.66); log qAFF (P = 0.95); log qAF3 (P = 0.48); log qAF6 (P = 0.4); and log qAF8 (P = 0.56). Stepwise regression analysis showed negative correlation between MPS II and log qAFF values (R2 = 0.35) with Spearman coefficient (ρ) of -0.60 (P < 0.01) and log qAF3 (R2 = 0.18; ρ = -0.38.; P < 0.01). No correlation was found between MPS II and log qAF6 (ρ = 0.01, P = 0.93), neither with log qAF8 (ρ = -0.05, P = 0.66). CONCLUSIONS: In young healthy subjects, a negative correlation between qAF values and MPODHFP was found in the central degrees. However, qAF and HFP do not seem to be interchangeable: they represent two opposite ways of estimating MP.