Purpose
This study compares in vivo measurements of MP obtained using customized heterochromatic flicker photometry (cHFP) (Densitometer), dual-wavelength autofluorescence (Heidelberg Spectralis) and single-wavelength reflectance (Zeiss Visucam).
Methods
MP was measured in one eye of 49 subjects using each of the three devices. Agreement between the Densitometer and Spectralis devices was investigated at various eccentricities (circa 0.25, 0.50, 1.00, and 1.75 degrees eccentricity), using a variety of quantitative and graphical methods (including Pearson correlation to measure degree of scatter (precision [prcn]), accuracy coefficient (acc) to measure shifts in location or scale, concordance correlation coefficient (ccc) calculated from the acc and prcn coefficients, paired t-test, and Bland-Altman plot). Because data at different eccentricities is not yielded from the Visucam, agreement between central MP using the Visucam and each of the other devices was investigated using regression methods.
Results
Agreement was strong between the Densitometer and Spectralis at all central eccentricities (e.g. at circa 0.25 degrees eccentricity: acc= 0.97, prcn= 0.90, ccc= 0.87). Regression analysis showed a very weak relationship between the Densitometer and the Visucam data (e.g. multiple regression of max MP from the Visucam on Densitometer MP at eccentricities 0.25 and 0.5 degrees had an associated R2 value of just 0.008 and was not statistically significant, p=0.843). Regression analysis also showed a weak relationship between MP measurements from the Spectralis and Visucam devices (e.g. multiple regression of max MP from the Visucam on Spectralis MP at eccentricities 0.23 and 0.27 degrees had an associated R2 value of just 0.047 and was not statistically significant, p=0.348). Regression results between readings obtained on the Visucam and those obtained on each of the other two instruments remained poor when orthogonal regression was used in place of ordinary least squares.
Conclusions
MP values obtained using the Heidelberg Spectralis are comparable to MP values obtained using the Densitometer. In contrast, MP values obtained using the Zeiss Visucam are not comparable with either the Densitometer or the Spectralis MP measuring devices. Taking cHFP as the current gold standard, the Spectralis is suitable for use in a clinical and research setting, whereas the Visucam is not.
Keywords: 587 macular pigment •
465 clinical (human) or epidemiologic studies: systems/equipment/techniques