Macular pigment optical density measurement by heterochromatic flicker photometry: Challenging a basic premise
Department of Physics, Florida International University, Miami, FL 33199, USA.
Research Article
World Journal of Advanced Research and Reviews, 2023, 18(01), 488–493
Publication history:
Received on 25 February 2023; revised on 10 April 2023; accepted on 12 April 2023
Abstract:
Measurement of macular pigment optical density (MPOD) in the human eye is important due to the protection it provides against certain eye diseases such as age-related macular degeneration. A commonly used psychophysical technique is heterochromatic flicker photometry (HFP). This technique assumes a uniformity in the retinal spectral sensitivity from the central fovea to the surrounding parafovea, areas of the retina employed in HFP. We show here that the MPOD spectrum obtained by HFP is characteristic of the carotenoids of which the macular pigment is composed, but only in the blue part of the spectrum. At longer wavelengths, in the red part of the spectrum, the measured MPOD was found to rise with increasing wavelength. We propose that this artefact is due to different contributions to retinal spectral sensitivity in the fovea and parafovea from long- (LWS) and medium-wavelength-sensitive (MWS) cones. By adjusting the LWS/MWS ratio, we could calculate potential retinal spectral sensitivities for the fovea and parafovea that would account for the apparent MPOD in the red part of the spectrum. An LWS/MWS ratio of 4.15 in the parafovea, relative to the fovea, provided the necessary correction, and had the additional effect of providing an increase in the measured peak MPOD at 460 nm. Caution is therefore warranted when using HFP to measure only the peak MPOD, as is commonly the case.
Keywords:
Macular Pigment; Heterochromatic Flicker Photometry; Retina; Fovea; Spectral Sensitivity
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Copyright © 2023 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0