Directional and nondirectional spectral reflection from the human fovea

Abstract

A model of the directional and nondirectional reflection spectrum of the human fovea is developed, incorporating reflectors, absorbers, and a wavelength-dependent optical Stiles-Crawford effect (OSCE). Data from 102 healthy subjects between 18 and 75 years obtained with the fundus reflection analyzer (FRA), an imaging spectrograph that measures the directional reflection profile of the human fovea in the pupil plane from 400 to 950 nm, were analyzed. Subgroups of young (<40 years) and old (>50 years) observers were defined. Mean results of the young group defined a template for directionality versus wavelength. For the whole group, mean reflection at 550 nm from the cones was 2.12%, from the retinal pigment epithelium 0.56%, and from the choroid 7.92%. Lens density, cone disc reflection, and blood layer thickness showed significant trends versus age. The model for the first time simultaneously describes the spectra of the directional and nondirectional reflection of the human fovea. Rayleigh scatter losses of the media and in preretinal layers were assumed zero in the nondirectional pathway. Mean density of the macular pigment of a subgroup (53 subjects, 19 to 75 years) correlated significantly with independent data from reflectance and autoflourescence images obtained by scanning laser ophthalmoscope (SLO) and data from flicker photometry.

Intraocular scattering compensation in retinal imaging

“…For the longer wavelengths, however, there is an additional parameter that needs to be taken into account: melanin pigmentation. As shown in previous studies, fundus reflectance at longer wavelengths depends heavily on melanin pigmentation [22][23][24][25]. Low pigmentation individuals show a much higher fundus diffusion at longer wavelengths that significantly affect the PSF even for larger angles.…”

Macular pigment optical density measurements: evaluation of a device using heterochromatic flicker photometry

“…Using known spectral characteristics of the different absorbers within the eye (lens, MP, melanin, blood), the densities of the pigments and percent reflectance at the interfaces are optimized to fit the measured data at all wavelengths. 25,26 For a detailed discussion of this analysis see Berendschot et al 27,28 …”

Measuring macular pigment optical density in vivo: a review of techniques

“…Berendschot and van Norren [141] also used a newer version of the device, the FRA 2, which has a number of differences from the first version, including being smaller, which makes it desktop-mountable. Kanis et al [143,148] and van de Kraats and van Norren [139] have also used the FRA 2 in their studies.…”

“…To achieve this, a detailed optical model of the pathways of light in the eye is required. A number of optical models of increasing complexity have been proposed over the years, from van Norren and Tiemeijer [133] through to van de Kraats and van Norren [139]. Probably the most familiar optical model is that derived by van de Kraats, Berendschot and van Norren [140], which has been used to work out MPOD in several studies [e.g., 58,136,[141][142][143][144].…”