Abstract
Purpose :
This presentation aims at introducing an optical coherence tomography (OCT)-based en face retinal imaging modality; pigment-and-flow imaging (PAF). Its concept, underlying technologies, and clinical cases are shown.
Methods :
PAF imaging is based on three key technologies including polarization diversity OCT (PD-OCT), multi-contrast three-dimensional (3D) image processing, and a motion-free imaging based on Lissajous scan.
The PD-OCT is a simplified version of polarization sensitive OCT, which provides 3D OCT, OCT angiography (OCTA), and degree-of-polarization-uniformity (DOPU) images. The DOPU image is known to highlight melanin in the retina and choroid.
The multi-contrast image processing generates a pseudo-color en face retinal image by using fully 3D information of OCTA and DOPU. The generated image simultaneously highlights vascular and RPE abnormality.
The en face image is totally motion free due to the Lissajous scan method, which is a combination of non-standard scanning trajectory and a specially designed 3D motion correction algorithm.
The combination of these three technologies finally gives a motion-free en face image which is sensitive to the abnormalities of the RPE and flow (PAF image).
126 cases were investigated by PAF imaging.
Results :
In the PAF image [Fig. 1(a)], the vessels are appeared with different colors according to the total amount of melanin above the vessels (yellow-red-blue from less to more melanin). So, retinal and choroidal vessels are respectively appeared as yellow and blue in normal eyes.
Figure 1 shows an example of myopic choroidal neovascularization. The en face OCT (b) presents abnormal hyper scattering (red circle), while it is not shown in OCTA (c). The PAF image (a) shows this abnormality as reddish appearance of retinal vessels and relatively yellowish appearance of choroidal vessels. The PAF image also highlights another abnormality (yellow circle) which are not appeared in the en face OCT and OCTA. The cross-sectional OCT (d) shows a hyper penetration in the choroid at this region, it would indicate melanin reduction at the RPE. Although it is hardly seen in the cross-sectional OCT (d), it is clearly highlighted in the PAF image (a).
Conclusions :
Three new OCT technologies enabled motion-free PAF imaging. Cases showed its quick highlighting ability of RPE and vasculature abnormality.
This is a 2020 Imaging in the Eye Conference abstract.