Abstract
Purpose :
Motion and blinking create unacceptable artifacts in optical coherence tomography angiography (OCTA). Commercial systems have deployed optical tracking systems to detect blinks and motion to allow extended scan time, but they add to the cost and complexity of the system. An extended field-of-view (FOV) OCTA requires a longer acquisition time and has a greater likelihood of these artifacts, making it essential that the system can minimize these artifacts. We present a novel, OCTA-based tracking method without hardware modification that achieves high-resolution, 75-degree field-of-view (FOV) OCTA with minimal motion artifacts.
Methods :
We developed a 400-kHz swept-source prototype OCT with a 1060 nm center wavelength and 100 nm bandwidth and a custom wide-field sample arm to realize 10-µm lateral resolution with a maximum 75-degree FOV. We scanned healthy and diabetic eyes with a high sampling density (2304 x 1408 lines over 23 × 12-mm), and instructed the participants to fixate in primary gaze and blink as needed. Highly efficient, graphic processing unit (GPU)-based software generated OCTA volume in real time. The algorithm included an instantaneous motion index that evaluates the strength of motion artifact on en face OCTA images and automatically rescans the areas with suprathreshold motion and eye blinking artifacts in real-time.
Results :
High-resolution 75-degree OCTA images were acquired from 52 diabetic retinopathy (DR) and 12 healthy participants. Each scan required less than one minute with self-tracking engaged. En face inner retinal OCTA were generated (Fig. 1). In 5% of subjects, excess motion prevented complete scan acquisition. The tracking system detected and eliminated 91.5% of motion artifacts. The resulting OCTA demonstrated capillary dropout, microaneurysms, and intraretinal microvascular abnormalities in high resolution with a FOV that exceeds the current commercial OCT systems.
Conclusions :
We have demonstrated an OCTA-based tracking system that generates high-resolution 75-degree FOV wide-field OCTA with minimal residual motion artifacts. This approach does not require additional optical hardware, and may be generalizable to a broad range OCTA systems.
This is a 2020 Imaging in the Eye Conference abstract.