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J. Ren, H. K. Gille, J. Wu, C. Yang; OCT Imaging of Collector Channels by PARS Endoscopic Probe. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3851.
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© ARVO (1962-2015); The Authors (2016-present)
To image and locate certain physiological structures like collector channels (CC) for glaucoma diagnosis and treatment such as bypass stent implantation, a paired angled rotating scanning (PARS) endoscopic probe is developed to acquire high-quality optical coherence tomography (OCT) images to facilitate anterior chamber examination.
Our prototype PARS probe consisted of stainless steel needles, 1.6mm in outer diameter and 63.5mm in length. Two segments of gradient-index lens were installed in the needles, focusing light to a working distance about 1.4mm (in air). A swept laser centered at 1310 nm with a scan range of 100 nm served as the OCT light source. The probe was positioned over a prepared human cadaver eye tissue. The trabecular meshwork was removed to mimic the situation when the probe’s tip is advancing into the Schlemm’s canal (SC). As the needles of the probe rotating, the beam was scanned across the wall of SC and OCT images were acquired. The system was configured at 0.5fps with 666 depth scans per frame.
The probe yielded a fan shape scan area with an arc angle about 40o. The spot sizes ranged 12~14 microns. Fig. 1(a) is the OCT image of a collector channel in the sample. As shown in the figure, both the opening to the SC’s wall and the collector channel going into the sclera were clearly imaged and can be quantitatively measured. Fig. 1(b) is the SEM image of the CC. Both methods agree with each other and indicate the opening was about 120 microns wide.
This research demonstrates that PARS endoscopic probe has sufficient resolution to resolve both the location and shape of collector channels. As it can be easily miniaturized, this forward-imaging probe can be potentially adapted to visualize the anterior chamber for clinical diagnosis and surgeries that require high-fidelity images.
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