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Macular pigment density estimated with Fourier-domain fundus reflectometry


Purpose : Since the macular pigment may have a protective role, the determination of its density is of clinical interest. Current methods for the measurement of macular pigment density (MPD) are either psychophysical, based on heterochromatic flicker photometry, or reflectometric, based on the analysis of multispectral images of the macula and the surrounding areas. While these techniques present some drawbacks, we proposed a new fast optical reflectometric method where there is no imaging of the fundus involved.

Methods : The method consists in projecting temporally modulated light of different wavelengths (blue: 480nm and green: 540nm) at two different areas of the fundus. Each source is divided in one disk and one concentric annulus that can be modulated independently. Both sources are projected simultaneously. The light returning from the fundus is detected with a photomultiplier. The Fourier transform of the signal reveals the relative reflectance of the macula and the surrounding area in each of the used wavelengths. The illumination and light-sensing arms are spatially separated at the pupil plane to eliminate unwanted effects of backscatter light and Purkinje reflections. The required pupil diameter for measurement is 4-mm and the total duration of the measurement was 270 msec. In this way the signal can be acquired within the latency interval of the pupillary response to the flash. An analysis of the signals provides with a direct estimate of MPD.

Results : The instrument was first calibrated using artificial eyes with colour absorption filers resembling the macular pigment. The instrument was also applied to healthy volunteers without the need of pupil dilation. The measurement procedure was brief and comfortable for the subjects. MPD estimates ranged from 0.22 to 0.32. Coefficients of variation ranged from 0.06 to 0.12 (or 6 to 12%).

Conclusions : A new optical instrument to perform in-vivo measurements of MPD was developed. It uses a simplified methodology over conventional multispectral imaging techniques. Since the instrument is easy to use and comfortable for patients it could be used in clinical environments to control MPD in patients

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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