Purpose:
To demonstrate the ability to obtain Doppler flow images of the human choroid with high speed Optical Frequency Domain Imaging (OFDI) at 1 µm.
Methods:
High-speed, high-resolution 1-µm OFDI was applied in vivo to the human eye of a healthy volunteer. Data acquisition was done at a speed of 100,000 axial scans/s over a depth range of 2.7 mm with an axial resolution of 5.0 µm in tissue. B-scans were acquired with 1500 axial scans over a lateral distance of 1.42 mm to obtain sufficient correlation of the speckle noise in subsequent axial scans. The Doppler phase accuracy of the system is measured to be 0.4 degrees as evaluated on a mirror. Phase difference maps were obtained to visualize the bi-directional blood flow in the choroid and retina.
Results:
Bi-directional blood flow was observed in both the choroidal and retinal regions. The imaging can pick up blood flow on blood vessels that are as small as 35 µm in diameter and as deep as the lower part of the choroid. Particularly in the choroidal region, blood flow can be detected in areas where the intensity image does not reveal the presence of blood vessel structures (see Figure 1).
Conclusions:
Doppler images from high-speed, high-resolution 1 µm OFDI measurements can be used to reveal bi-directional blood flow in the human choroid. Because it reveals additional information apart from the intensity images, it has the potential for better visualization and therefore better evaluation of the blood perfusion in the choroid.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • choroid • retina