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Scattering properties of the retina and the choroids determined from OCT-A-scans
H Hammer1, D Schweitzer, E Thamm
1University of Jena, Department of Ophthalmology, Germany.
Goal:
To determine the coefficient and the anisotropy of scattering as well as the refractive indices in the retina and in the choroid noninvasively in vivo.
Methods:
The power of coherent reflected light versus fundus depth is recorded in OCT-A-scans. The ratio of refractive indices is derived from the height of the reflection peaks. Provided that the absorption coefficient is known from fundus reflectometry, the scattering coefficient and anisotropy are calculated from the offset and the slope of the signal behind the reflection peaks on the basis of a single backscattering model.
Results:
We found scattering coefficients of 12/mm (retina) and 27.5/mm (choroid) as well as anisotropy values of 0.97 (retina) and 0.90 (choroid).
Discussion:
The OCT is usually employed for the measurement of intraocular distances. The new technique described here gives the unique opportunity to determine further interesting parameters of single ocular layers. The values given above are in good agreement with in vitro results.