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Hessam Roodaki, Anne-Marie Jablonka, Niklas Alexander Maierhofer, M. Ali Nasseri, Chris Patrick Lohmann, Abouzar Eslami; Big-bubble DALK under 4D OCT: an ex-vivo porcine trial. Invest. Ophthalmol. Vis. Sci. 2020;61(9):PB002.
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Microscope-integrated Optical Coherence Tomography (MIOCT) provides continuous monitoring of the surgical scene with high resolution and in a depth-resolved manner. With faster and higher resolution OCT engines, reconstruction and visualization of the entire surgical scene is feasible. This work investigates the possibility of performing a surgical task observed solely under continuous volumetric OCT. For this purpose, the air injection step in Deep Anterior Lamellar Keratoplasty (DALK) using the big-bubble technique is attempted.
A Lumera 700 microscope with RESCAN 700 (Zeiss, Oberkochen, Germany) is modified to carry out continuous volumetric OCT acquisitions covering a region of 6mm × 6mm and 2mm in depth. The acquired volumes are visualized using the Maximum Intensity Projection (MIP) technique on a monitor in front of the surgeon. Adaptive piecewise color transfer functions are in place that ensure the corneal stroma is portrayed nearly transparent and the endothelial and epithelial layers and the needle are visualized in red. The surgeon inserts a 30G needle attached to a custom-built 6 degrees of freedom (6DoF) master-slave robot into the cornea while observing the OCT visualization.
Air injection with the described system was attempted on ex-vivo porcine eyes (N=7) by two medical students with minimal prior experience in DALK performed on porcine models. Perforation of the endothelium was observed in one case and pneumodissection happened successfully in the remaining six cases with deep air deposits. Performance under 4D OCT visualization was considered superior to conventional microscopic view overlaid by continuous cross-sectional OCT acquisitions by the operators. A great advantage of the proposed method over conventional microscopic view and cross-sectional OCT was considered to be the lack of necessity to continuously reposition the OCT scan location.
Nominal surgical performance under continuous volumetric OCT acquisitions covering a large portion of the surgical field is feasible. Employing such imaging systems in combination with surgical robots has the potential to provide a superior platform for surgical tasks.
This is a 2020 Imaging in the Eye Conference abstract.
4D view of cornea with the needle tip close to the Descemet's membrane.
4D view of cornea, the induced tunnel and the deposited air over the Descemet's membrane.
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