RT Journal Article
A1 Vienola, Kari
A1 Braaf, Boy
A1 Sheehy, Christy
A1 Yang, Qiang
A1 Tiruveedhula, Pavan
A1 Arathorn, David
A1 de Boer, Johannes
A1 Roorda, Austin
T1 Imaging of optic nerve head pore structure with motion corrected deeply penetrating OCT using tracking SLO
JF Investigative Ophthalmology & Visual Science
JO Invest. Ophthalmol. Vis. Sci.
YR 2013
VO 54
IS 15
SP 1452
OP 1452
SN 1552-5783
AB  PurposeTo remove the eye motion and stabilize the optical frequency domain imaging (OFDI) system for obtaining high quality images of the optic nerve head (ONH) and the pore structure of the lamina cribrosa. MethodsAn optical coherence tomography (OCT) instrument was combined with an active eye tracking system to compensate for eye motion in OCT imaging. The OCT system was a phase-stabilized deeply penetrating OFDI system operating at center wavelength of 1040 nm and the eye tracker was an 840 nm scanning laser ophthalmoscope (SLO). Retinal tracking was performed using real-time analysis of the distortions within SLO frames. OFDI had axial resolution of 4.8 µm (6.5 µm in air) and the theoretical spot-size on the retina was 13.7 µm. Eye motion was reported at a rate of 960 Hz and motion signals were inverted to correction signals and used to keep the OCT scanning grid locked on the same retinal area throughout the measurement. In the case of a tracking lock failure (e.g. blink or large saccade), the tracker signaled the OFDI system to rescan corrupted B-scans immediately stepping back 10 B-scans and holding the position until signal was valid again. The achieved tracking bandwidth was 32 Hz due to an internal time lag of the hardware. The ONH of a healthy volunteer was imaged over an area of 2.7 × 2.7 mm (8.8°) using 700 A-scans/B-scan. To visualize the benefit of the tracking, each acquired B-scan in a volume dataset (total of 700 B-scans) was integrated over depth to create an enface image of the ONH. ResultsThe ONH was successfully imaged with negligible artifacts from eye motion (Fig. 1). On the left side, the whole dataset is seen including the duplicate corrupted B-scans. The corrupted B-scans were then removed in post-processing, thus leaving the undistorted duplicates untouched. The measured residual motion in the OCT B-scans was 0.32 arcmin (~1.6 µm) in a human eye. Four volumes from the same location were registered together to visualize the lamina cribrosa throughout the different depth slices of the eye (Fig. 2). The pore structure was clearly visible up to 430 um from the bottom of the ONH cup. ConclusionsIt is possible to obtain high quality OCT images from ONH and lamina cribrosa by compensating the eye motion during the measurements.  Enface images of the ONH over 2.7 × 2.7 mm field of view. Scale bar 1 deg.    C-scans extracted from different depths from the ONH dataset.   
RD 3/5/2021