Purpose:
To compare the scattering properties of different retinal segments in optical frequency domain imaging (OFDI) at 850nm and 1050nm.
Methods:
OFDI systems at 850nm and 1050nm were constructed for in vivo retinal imaging at 30k A-line rate. Retinal images were acquired on the same subject using the same human interface. We present a comprehensive image process solution that matches the scattering pixels in three-dimensional retinal volumes acquired at the two wavelenths to facilitate more accurate comparison of layered ocular fundus scattering.
Results:
Retinal volumetric images were taken from 850nm and 1050nm OFDI. The overlapped common volumes were sectioned and point-wise matched. The relative scattering intensity from different layers such as retinal nerve fiber layer (RNFL), photoreceptor, retinal pigment epithelium (RPE) and choroid were estimated. When the scattering intensity measurements were normalized on the total optical power backscattered from the retinal layers above the RPE, the 1050nm system has at least 6 dB more signal from choroidal tissues compared to the 850nm system. The relative scattering intensity in the RNFL (IRNFL) and RPE (IRPE) was determined at 850 and 1050 nm. The scattering intensity ratio of IRNFL / IRPE at 1050 nm was about 4 to 5 dB smaller than at 850nm.
Conclusions:
By fine matching the structures of scattering points, important optical properties such as scattering, absorption, and attenuation of the layered human retinal segments can be characterized. 1050nm and 850nm OFDI systems have different scattering and attenuation properties for different structures in human retina. As a result, they produce different tissue imaging contrast.
Fig. 1: One fine-matched cross sectional human retina image pair from 850nm (left) and 1050nm (right) OFDI systems.
Keywords: retina • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • image processing