![]() ![]() Scanning occurs within the probe and does not require an external means for moving the probe in order to obtain B-mode images. ![]() The miniature probe passes through the now standard 23-gauge (0.64 mm) and 25-gauge (0.51 mm) surgical instrument ports to permit real-time intraocular imaging. Joos and Shen developed a 25-gauge (0.51 mm outer diameter) hand-held forward-imaging B-scan OCT probe and demonstrated its feasibility for ophthalmic examination including retinal tissue. This fiberoptic common-path OCT was coupled to the side of a modified commercial forceps to provide A-scan precision depth sensing. However, the entire instrument must move back and forth inside the eye only 1.6 mm above the retinal surface to produce two-dimensional B-scan images, while using external metrology for tracking the probe tip movement. ![]() īalicki, et al., was first to demonstrate an A-mode single fiber common-path OCT probe combined with a 25-gauge pick for retinal applications. Besides imaging macular pathology, an intraocular probe would be able to transmit direct images of peripheral membranes and lesions without the distortions inherent in peripheral images with external OCT systems. A miniature probe would permit cross-sectional images of epiretinal membranes and their edges thus enabling surgeons to scan the retina to determine if the membrane peeling was satisfactorily completed prior to removing the instruments. In addition, an intraocular probe would bypass media obstructions including corneal opacities, miosis, and lenticular opacities that degrade an external OCT image. A forward-viewing intraocular surgical B-scan OCT probe co-planar with an intraocular instrument would provide a mechanism to bypass these issues and directly view the tissue structures in real time. Surgical limitations have included the complete blockage of the underlying retinal image by shadowing from standard stainless steel intraocular instruments, as well as problematic tracking of instrument movements within the OCT image, thus reducing useful real-time surgical guidance. Artifacts of motion, variable illumination, and tilt affect 3D-OCT images necessitating ongoing post-processing algorithm developments for static clinical 3D-OCT images. Three-dimensional surgical systems are also being developed. Improvements have been made to permit imaging during a procedure. Several other surgical microscope-mounted OCT systems with heads-up displays are being developed to provide real-time visualization in the operating room for anterior segment, and for posterior segment surgeries. performed a foundational study with an external microscope-mounted OCT operating room system to image retinal changes immediately following surgical manipulations. published the first approach to using intraoperative OCT imaging with a handheld external device to evaluate the retina prior to incision, and to evaluate retinal changes and procedure completeness during planned interruptions of the surgical procedures. Improved real-time intraoperative location of these edges would improve success rates of complete membrane removal and would reduce the use of potentially toxic dyes to visualize the membranes. Peri-operative scans, including handheld or microscope-coupled systems, produce information regarding the extent and location of vitreomacular traction, macular holes, and visually significant epiretinal membranes including characterization of membrane edges. This imaging modality provides valuable depth information of various disease processes within the retina. Optical coherence tomography (OCT) has become widely used as an important diagnostic and surgical pre-planning tool in ophthalmology. ![]()
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