Abstract
Purpose :
The high scattering mass, for example calcified drusen, often casts a scattering tail artifact that masks the ability to delineate Bruch’s membrane and choriocapillaris in the OCT imaging. The purpose of this study is to examine the influence of scattering tail artifacts on the measurement of the structures and blood flow beneath by purposely-designed phantom experiments.
Methods :
A three-layer phantom was designed and fabricated to mimic the optical properties of the retinal pigment epithelium (RPE) complex with the inclusions of high scattering masses, for example calcified drusen and hyperreflective foci. The top layer consisted of agar and 1-5% titanium oxide (TiO2) droplets, which provided high scattering properties to simulate intraretinal hyperreflective foci and calcified drusen. The middle layer was a thin empty channel for liquid flow representing the choriocapillaris or choroidal flow. And the bottom layer was a highly scattering solid base to mimic the sclera. 5% intralipid was injected into the channel to create dynamic flow. The phantom was imaged using a home-built SS-OCT with a central wavelength of 1310nm, and 3D OCT, and OCTA images were obtained.
Results :
The phantom model showed that the high scattering mass generated scattering tails below it due to its multiple light scattering properties (Fig 1a, e). The tails attenuated the probing light, reducing the OCT and OCTA signals detected from structures beneath (Fig 1a-f). When the concentration of high scattering mass exceeds a certain threshold, the OCT and OCTA signals beneath cannot be detected as shown by the red arrow in Figure 2. However, the artifact did not create artificial OCTA signals, and real flow below the mass was indicated even with apparent scattering tails (Fig 1g and Fig 2e).
Conclusions :
The results of this study suggest that the detection of blood flow within the high scattering tail is possible, but only to a level when the OCT light can survive high scattering mass to reach the structures beneath. The experimental results imply that the detection of the choriocapillaris under the highly scattering mass, such as calcified drusen, is complicated, highlighting the need for compensation and additional scrutinization in the quantification of choriocapillaris flow deficits.
This abstract was presented at the 2023 ARVO Imaging in the Eye Conference, held in New Orleans, LA, April 21-22, 2023.