(B-78) Handheld Point-of-Care Ophthalmic Diagnostics using Spectrally Encoded Coherence Tomography and Reflectometry

Introduction:: Optical coherence tomography (OCT) benefit clinical diagnostic imaging in ophthalmology by enabling volumetric visualization of the retina. Commercially available OCT utilize a slit-lamp design that precludes imaging of bedridden, uncooperative, and pediatric patients. Point-of-care OCT research prototypes have demonstrated imaging of supine patients [1-5]. We previously demonstrated OCT imaging using handheld spectrally encoded coherence tomography and reflectometry (HH-SECTR). Our previous prototype was limited by: 1) poor alignment stability; 2) lossy spectrally encoded reflectometry (SER) optical throughput; and 3) cumbersome manual focus adjustment. Here, we demonstrate optical design improvements to increase optical power throughput; a modular aluminum probe design that ensures clinical robustness in a compact and lightweight form-factor; and a mechanical focusing subsystem. These improvements benefit HH-SECTR clinical translation for point-of-care ophthalmic diagnostics.

Materials and Methods:: Our previous optical design was modified with broadband dielectric fold mirrors and an off-axis parabolic mirror collimator to further improve SER optical throughput. To ensure HH-SECTR mechanical stability and clinical robustness for supine imaging, we implemented a modular aluminum probe chassis consisting of machined mounts and a dual-sided baseplate to house imaging optics and optomechanics. The overall layout was optimized into a form-factor for ergonomic handheld imaging of supine patients. Ocular refractive power correction between patients was implemented to ensure optimal image quality, we implemented a mechanical focus-adjust subsystem into HH-SECTR. A bipolar stepper motor and custom linear actuation system perform mechanical translation of the ophthalmic lens within the HH-SECTR handgrip. The focusing system allows refractive power correction from -15 to +15 diopters and can enable pediatric imaging.

Results, Conclusions, and Discussions:: In vivo human retinal imaging was performed on healthy adult volunteers under an internal review board approved protocol. Imaging was performed using a 400 kHz 1060 nm swept-source engine. SER images were sampled at 2048 x 1000 for a frame rate of 400 Hz. OCT volumes were simultaneously sampled at 2048 x 1000 x 1000 for a volume acquisition time of 2.5 seconds. The improved optical design and quantified alignment increased SER and OCT power throughput through the system by 100% and 33%, respectively, in comparison to our previous prototype. The modular aluminum chassis of the HH-SECTR probe measures 24.8 cm x 8.7 cm x 13.8 cm. Mechanical focusing is demonstrated using a stationary model eye and stepping through ± 10 diopters of focal shift, with noticeable change in the field-of-view. SER and OCT projections display the optic nerve head, fovea, and retinal vasculature, while OCT cross-sections at the optic nerve head display the inner retina, outer retina, and choroid.

Acknowledgements (Optional): : This research was supported by Vanderbilt University, the Vanderbilt Institute for Surgery and Engineering (VISE) and the US National Institutes of Health Grants R01-EY030490, R01-EY031769, and R01-EY033969. The content was solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

References (Optional): : [1] Lu, Chen D., et al. "Handheld ultrahigh speed swept source optical coherence tomography instrument using a MEMS scanning mirror." Biomedical Optics Express 5.1 (2014): 293-311.
[2] Song, Shaozhen, et al. "Development of a clinical prototype of a miniature hand-held optical coherence tomography probe for prematurity and pediatric ophthalmic imaging." Biomedical Optics Express 10.5 (2019): 2383-2398.
[3] Ni, Shuibin, et al. "High-speed and widefield handheld swept-source OCT angiography with a VCSEL light source." Biomedical Optics Express 12.6 (2021): 3553-3570.
[4] Campbell, J. Peter, et al. "Handheld optical coherence tomography angiography and ultra–wide-field optical coherence tomography in retinopathy of prematurity." JAMA Ophthalmology 135.9 (2017): 977-981.
[5] Viehland, Christian, et al. "Ergonomic handheld OCT angiography probe optimized for pediatric and supine imaging." Biomedical Optics Express 10.5 (2019): 2623-2638.