Optical coherence tomography (OCT) allows for micron scale imaging of the human retina and cornea. Current generation research and commercial intrasurgical OCT prototypes are limited to live B-scan imaging. Our group has developed an intraoperative microscope integrated OCT system capable of live 4D imaging. With a heads up display (HUD) 4D imaging allows for dynamic intrasurgical visualization of tool tissue interaction and surgical maneuvers. Currently our system relies on operator based manual tracking to correct for patient motion and motion caused by the surgeon, to track the surgical tool, and to display the correct B-scan to display on the HUD. Even when tracking only bulk motion, the operator sometimes lags behind and the surgical region of interest can drift out of the OCT field of view. To facilitate imaging we report on the development of a fast volume based tool segmentation algorithm. The algorithm is based on a previously reported volume rendering algorithm and can identify both the tool and retinal surface. The algorithm requires 45 ms per volume for segmentation and can be used to actively place the B-scan across the tool tissue interface. Alternatively, real-time tool segmentation can be used to allow the surgeon to use the surgical tool as an interactive B-scan pointer.
Ophthalmic surgeons manipulate micron-scale tissues using stereopsis through an operating microscope and instrument
shadowing for depth perception. While ophthalmic microsurgery has benefitted from rapid advances in instrumentation
and techniques, the basic principles of the stereo operating microscope have not changed since the 1930’s. Optical
Coherence Tomography (OCT) has revolutionized ophthalmic imaging and is now the gold standard for preoperative and
postoperative evaluation of most retinal and many corneal procedures. We and others have developed initial microscope-integrated
OCT (MIOCT) systems for concurrent OCT and operating microscope imaging, but these are limited to 2D
real-time imaging and require offline post-processing for 3D rendering and visualization. Our previously presented 4D
MIOCT system can record and display the 3D surgical field stereoscopically through the microscope oculars using a
dual-channel heads-up display (HUD) at up to 10 micron-scale volumes per second. In this work, we show that 4D
MIOCT guidance improves the accuracy of depth-based microsurgical maneuvers (with statistical significance) in mock
surgery trials in a wet lab environment. Additionally, 4D MIOCT was successfully performed in 38/45 (84%) posterior
and 14/14 (100%) anterior eye human surgeries, and revealed previously unrecognized lesions that were invisible
through the operating microscope. These lesions, such as residual and potentially damaging retinal deformation during
pathologic membrane peeling, were visualized in real-time by the surgeon. Our integrated system provides an enhanced
4D surgical visualization platform that can improve current ophthalmic surgical practice and may help develop and
refine future microsurgical techniques.
The first generation of intrasurgical optical coherence tomography (OCT) systems displayed OCT data onto a separate computer monitor, requiring surgeons to look away from the surgical microscope. In order to provide real-time OCT feedback without requiring surgeons to look away during surgeries, recent prototype research and commercial intrasurgical OCT systems have integrated heads-up display (HUD) systems into the surgical microscopes to allow the surgeons to access the OCT data and the surgical field through the oculars concurrently. However, all current intrasurgical OCT systems with a HUD are only capable of imaging through one ocular limiting the surgeon’s depth perception of OCT volumes. Stereoscopy is an effective technology to dramatically increase depth perception by presenting an image from slightly different angles to each eye. Conventional stereoscopic HUD use a pair of micro displays which require bulky optics. Several new approaches for HUDs are reported to use only one micro display at the expense of image brightness or increased footprint. Therefore, these techniques for HUD are not suitable to be integrated into microscopes. We have developed a novel stereoscopic HUD which uses spatial multiplexing to project stereo views into both oculars simultaneously with only one micro-display and three optical elements for our microscope-integrated OCT system. Simultaneous stereoscopic views of OCT volumes are computed in real time by GPU-enabled OCT system software. We present, to our knowledge, the first microscope integrated stereoscopic HUD used for intrasurgical OCT with a novel optical design for stereoscopic viewing devices and report on its preliminary use in human vitreoretinal surgeries.