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Editors Selection IGR 17-4
Anatomical Structures: Visualizing the Collector Channel Entrance
Comment by Murray Johnstone on:
72921 Imaging collector channel entrance with a new intraocular micro-probe swept-source optical coherence tomography, Xin C; Chen X; Li M et al., Acta Ophthalmologica, 2017; 95: 602-607
See also comment(s) by Sung-Chul Park •The authors of this report describe a new intraocular OCT probe capable of imaging the outflow system from either the anterior chamber or from within Schlemm's canal. Their report demonstrates the ability to identify the collector channels in the distal aqueous outflow pathways from either of the two locations.
The approach employs several technological advances, eliminating the issues of scleral light scattering and shadowing from the limbal vasculature that occurs with current commercial systems. Advances include: 1) small catheter size permitting positioning near the tissue, 2) a 1310 nm vs. the typical 810 nm light source permitting better tissue penetration, 3) a high scan rate (50 kHz) within a very thin probe (0.25 mm), and 4) swept source OCT implementation improving detection sensitivity over the imaging depth.
A commercial version of such a microprobe would have the potential to much more efficiently target the collector channels of the distal outflow system, a capability not available previously. Both accurate localization and assessment of functional properties of the distal outflow channels have the potential to substantially improve success rates of MIGS such as stents.
Current limitations to in vivo applications result from both structure and time resolution limits imposed by the frame rate and small size of the probe (0.25 mm). Fortunately, the authors suggest an increase in probe size, for example to the size of a 3-mm corneal incision, should provide the ability to achieve the required resolution. Since many MIGS surgeons do cataract surgery involving incisions approximating 3 mm, the more substantial probe size is unlikely to be a deterrent to use of a bigger probe.
The availability of a substantial increase in the probe dimensions, together with rapid advances in the development of light sources for swept source OCT, suggests OCT innovators will overcome current probe limitations soon. One of the most exciting aspects of this report is the demonstration of the rapid advances in OCT technology and its minia-turization that are quickly transforming our field.
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