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Derek Nankivil, Gar Waterman, Brenton Keller, Anthony N Kuo, Joseph A Izatt; Handheld Convertible Anterior/Posterior Segment Swept Source Optical Coherence Tomography System. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1313.
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© ARVO (1962-2015); The Authors (2016-present)
Build a swept source optical coherence tomography (SSOCT) imaging system that uses coherence revival to image both the anterior and posterior segments with a single handheld microelectromechanical systems (MEMS)-based optical probe.
An SSOCT system with a Mach-Zehnder topology was constructed using an Axsun Technologies laser with a central wavelength of 1040 nm, a 100 nm bandwidth, and a 100 kHz sweep rate. The retinal path was matched to the reference path, giving a conventional configuration. Coherence revival was used to encode the anterior segment beam with a carrier frequency, effectively creating a complex conjugate resolved extended-depth heterodyne SSOCT system.<br /> The diffraction-limited optical design gave a predicted lateral resolution of 8.6 μm and a FOV of 20° for the posterior segment system. The anterior segment system has a lateral resolution of 23.6 μm, a depth of focus of 3.6 mm, and an 11.2 mm square FOV. The measured axial resolution for both paths was 6.9 µm.<br /> A miniature motorized commercial translation stage and a bistable rotary solenoid powered the motion systems that provide the ability to adjust for patient refraction and to toggle between measurement modes. A gimbal-less two-axis scanning MEMS micromirror was used to control beam position. The entire probe weighs less than 1.2 lbs with a form factor of 8 x 3¾ x 3½ in.
The peak sensitivity was 98 and 102 dB for the anterior and posterior segment channels, respectively. For the posterior segment channel, we observed a -6dB imaging range of 4.6 mm. For the anterior segment channel, the peak sensitivity position appeared at approximately 5 mm in depth, and the -6dB imaging range spanned 9.5 mm from 0.25 mm to 9.75 mm.<br /> To demonstrate the applicability of dual depth SSOCT in vivo, anterior segment and retinal images were acquired from healthy human volunteers using bench-top mock-ups similar to the handheld design.
A MEMS-based handheld dual depth SSOCT system design that enables sequential imaging of the anterior segment and retina was demonstrated.
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