OCT angiography guided by SLO eye tracker

Abstract

Purpose: To demonstrate applicability of recently developed Scanning Laser Ophthalmoscope combined with Optical Coherence Tomography technique for noninvasive visualization of retinal microcapillary network (RMN) in retinal diseases. RMN maps are provided by OCT technology while SLO provides fast eye tracking system.

Methods: The study was performed with high resolution and high speed spectral OCT (100 kHz A-scan rate, 4.5 um axial resolution, 91 dB detection sensitivity). Constant 30 Hz retinal preview is provided by SLO device and is used to guide the OCT scanning to the region of interest. Dedicated algorithm is used to detect eye motion on SLO images and calculate the translation to update the OCT scanner trajectory to compensate the motion of the eye. Complex difference and phase-variance algorithms are used to provide flow contrast on RMN maps. To increase RMN visualization area mosaic protocols were used. In case of eye blink or data corruption OCT guided by SLO can still provide good quality RMN maps as corrupted B-scans are rejected and reacquired.

Results: RMN maps obtained in the eyes of healthy volunteers and 12 patients with diabetic retinopathy, branch retinal vein occlusion and central retinal vein occlusion will be presented. 3D data will be visualized including depth color-coded projection. We will show that OCT can easily identify no perfusion areas and can visualize superficial and deep capillary plexus independently. We compare complex difference and phase-variance algorithms for RMN maps generation.

Conclusions: Recent reports on OCT angiography techniques show that these methods are well suited for visualization of 3D RMN in the healthy and pathologic eyes as well. However data acquisition time still needs to be shortened in order to provide good quality maps. Having no possibility to dramatically shorten time measurement we focused on small tracked areas that can be finally integrated on wide field mosaic. Our data suggest that OCT angiography has potential in the early diagnosis of retinal vascular diseases. Moreover real time eye tracking system highly improves data acquisition quality.