Macular Pigment Density and Quantitative Fundus Autofluorescence in Young Healthy Subjects

To measure macular pigment (MP) and find possible correlation between heterochromatic flicker photometry (HFP) and quantitative autofluorescence (qAF) in young healthy subjects.

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.

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).

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.