Purpose: The macular pigment is thought to have a protective role to the retina and recently it has been related to Age-related Macular Degeneration. Despite its potential importance in retinal health, the assessment of the amount of pigment is not yet routinely performed. This is partially due to the lack of a fast and accurate instrument that could measure the Macular Pigment Optical Density (MPOD) objectively. In this work, we present a new objective optical method for the rapid and accurate measurement of MPOD.
Methods: The retinal fundus is illuminated using light sources of two different wavelengths, 450nm and 550nm, and two field shapes, a foveal disk and a concentric peripheral annulus. Each source flickered at a distinct temporal frequency. The reflected light from the fundus was focused on a high-speed photodetector and the amplitude of the signal’s components, corresponding to the four sources, was extracted using Fourier analysis. The measured amplitudes were then used to calculate the MPOD. The optical system also featured a fundus camera, which allowed the reconstruction of the spatial distribution of the MP. The measurement process lasts less than a minute for each eye, including alignment. We measured the MPOD of both eyes of 13 healthy volunteers of mean age 33.4±8.3 years. For two of the volunteers, we also estimated the MPOD spatial distribution. The MPOD of ten of the volunteers was also measured using a psychophysical commercial device (MPSII; Electron Technology) for comparison.
Results: The average MPOD value for the 13 subjects using our method was found to be 0.37±0.07D.U., similar to those values found by in previous studies using the reflectometry method. We assessed the repeatability of the instrument using the Bland Altman analysis and it showed a very low bias (0.004) and narrow limits of agreement (0.048-0.040). The instrument was compared for 10 subjects (19 eyes) against a commercially available instrument. It has shown good correlation (p<0.005) but low agreement that can partially be attributed to the difference in the parameters of each instrument.
Conclusions: We have designed and built a new optical method to measure the macular pigment density. The instrument has shown high repeatability and good correlation with a commercial psychophysical instrument. It can potentially serve as a non-midriatic, low-cost and quick standalone setup for the clinical measurement of macular pigment optical density.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 – May 2, 2019.