Abstract
We describe the first handheld, swept source optical coherence tomography (SSOCT) system capable of imaging both the anterior and posterior segments of the eye in rapid succession. A single 2D microelectromechanical systems (MEMS) scanner was utilized for both imaging modes, and the optical paths for each imaging mode were optimized for their respective application using a combination of commercial and custom optics. The system has a working distance of 26.1 mm and a measured axial resolution of 8 μm (in air). In posterior segment mode, the design has a lateral resolution of 9 μm, 7.4 mm imaging depth range (in air), 4.9 mm 6dB fall-off range (in air), and peak sensitivity of 103 dB over a 22° field of view (FOV). In anterior segment mode, the design has a lateral resolution of 24 μm, imaging depth range of 7.4 mm (in air), 6dB fall-off range of 4.5 mm (in air), depth-of-focus of 3.6 mm, and a peak sensitivity of 99 dB over a 17.5 mm FOV. In addition, the probe includes a wide-field iris imaging system to simplify alignment. A fold mirror assembly actuated by a bi-stable rotary solenoid was used to switch between anterior and posterior segment imaging modes, and a miniature motorized translation stage was used to adjust the objective lens position to correct for patient refraction between -12.6 and + 9.9 D. The entire probe weighs less than 630 g with a form factor of 20.3 x 9.5 x 8.8 cm. Healthy volunteers were imaged to illustrate imaging performance.
Highlights
As optical coherence tomography (OCT) develops into an important tool for anterior segment characterization, the ability to use a single instrument for both anterior and posterior segment imaging may become a desirable feature for clinical systems
All of the hardware was controlled using custom graphics processing unit (GPU)-accelerated software written in C++ to provide real-time display of OCT images
We have demonstrated a microelectromechanical systems (MEMS)-based handheld dual depth swept source optical coherence tomography (SSOCT) system that enables rapid, sequential imaging of the anterior segment and retina
Summary
As optical coherence tomography (OCT) develops into an important tool for anterior segment characterization, the ability to use a single instrument for both anterior and posterior segment imaging may become a desirable feature for clinical systems. Several commercial ophthalmic OCT systems are capable of switching between anterior and posterior imaging modes; this requires the addition or removal of optics from the sample path and adjustment of the reference path. A few of these instruments are capable of imaging both the anterior and posterior segment [2,3,4, 7], but switching between modes requires the operator to remove and/or add an additional lens or lens system. This distracts the operator from the patient and requires realignment with the patient eye after switching modes
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