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S. Han, M. V. Sarunic, J. Wu, M. Humayun, C. Yang; Hand-Held Forward-Imaging Needle Probe for Endoscopic OCT Inspection of the Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):161.
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To develop a miniature endoscopic probe compatible with fourier-domain optical coherence tomography (FDOCT) which provides lateral beam steering across the posterior segment for 2D sub-surface retinal imaging during surgery. Fiber optic delivery allows retinal imaging with 1310 nm light permitting higher optical power and deeper tissue penetration for visualization of choroidal microvasculature. The scanning probe is compatible with in situ delivery of high optical power for tissue welding procedures.
We present a forward imaging probe housed in a 21-gauge needle (0.82mm outer diameter) specifically designed for endoscopic ophthalmic surgeries performed through cannulated incisions in the sclera. Two dimensional B-scan cross-sectional images were obtained by steering the depth-resolved FDOCT beam across the surface of the posterior segment using paired angled rotating scanning (PARS). The probe and DC-motor were assembled in a light-weight hand-held chassis. The optical system was designed for a commercial 1310-nm wavelength swept laser, but is compatible with any fiber coupled light source.
Our scanning needle probe prototype has a lateral scan range of 0.66 mm at a 1 mm working distance. The lateral and axial resolution were 9.2 µm and 9.3 µm, respectively. Intraocular imaging with the needle probe was demonstrated on enucleated porcine eyes with the vitreous humor removed. The acquired images revealed details of retinal detachment and residual vitreous humor above the retina. The lack of well defined retinal layers is due to rapid tissue deterioration of the ex vivo samples.
Scanning endoscopic retinal cross-sectional imaging was demonstrated for sub-surface visualization of retinal and choroidal structures. Further pre-clinical investigation of the miniature beam steering probe is motivated for high speed imaging during surgical procedures on the posterior segment and potential application in retinal laser surgery.
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