![]() Compared to the shorter wavelengths used in retinal imaging, the 1310 nm range has reduced tissue scattering and allows deeper penetration into the iris, sclera, and anterior chamber angle 10. The prototype SS-OCT instrument uses a microelectromechanically actuated, wavelength tunable, vertical-cavity surface-emitting laser (MEMS-VCSEL) operating in the 1310 nm wavelength range. The unique combination of high 325 kHz A-scan speed, long 15.5 mm imaging range, dynamic focal plane adjustment, and versatile wide field OCT and OCTA imaging represents significant improvements over existing instruments. This study reports the development of swept-source OCT (SS-OCT) technology that combines advancements in light source, optics, mechanical design, and signal processing to address the challenges of anterior eye imaging. Misalignment and motion can cause errors in biometry, as well as introduce parasitic noise in OCTA. Anterior eye imaging requires accurate positioning and detection of eye movements. ![]() To cover the entire anterior eye range, achieve sufficient penetration, or reach the scan speed required for OCTA, commercial and earlier prototype instruments often tradeoff imaging resolution, speed, range, and/or functionality 9. Some anterior eye tissues, such as the iris and sclera, are highly turbid and limit imaging to more superficial layers. Anatomically, the anterior segment extends from the corneal surface to the lens capsule, or approximately 8 mm in normal adult eyes. The requirements and challenges for anterior eye OCT imaging differ from its retinal counterpart. Recent clinical applications, including anterior ocular biometry, investigating corneal and lenticular pathologies, angle assessment in glaucoma, and OCTA for the anterior segment vasculature, spurred the development of OCT technologies designed specifically for the anterior eye 6, 7, 8, 9. Anterior eye OCT imaging was demonstrated shortly after the invention of OCT 5. Optical coherence tomography (OCT) and OCT angiography (OCTA) have become indispensable in ophthalmic clinics, imaging depth-resolved structure and microvasculature with exquisite detail 1, 2, 3, 4. We present structural and angiographic OCT images of the anterior eye, demonstrating the unique imaging capabilities using representative scanning protocols which may be relevant to future research and clinical applications. Improved optical and mechanical design, including parallax “split view” iris cameras and stable, ergonomic patient interface, facilitates accurate instrument positioning, reduces patient motion, and leads to improved imaging data yield and measurement accuracy. Dynamic focusing using a tunable liquid lens extends the effective depth of field while preserving the lateral resolution. Dual channel recording of the OCT and calibration interferometer fringe signals, as well as sweep to sweep wavenumber compensation, is used to achieve invariant 12.2 µm (~ 9.1 µm in tissue) axial resolution and optimum point spread function throughout the depth range. Achieving high speed and long range requires linearizing the VCSEL wavenumber sweep to efficiently utilize analog-to-digital conversion bandwidth. The 1310 nm wavelength range enables structural OCT and OCTA deep in the sclera and through the iris. The 15.5 mm (~ 11.6 mm in tissue) depth range spans all optical surfaces from the anterior cornea to the posterior lens capsule. The ultrahigh 325 kHz A-scan rate not only facilitates biometry measurements by minimizing acquisition time and thus reducing motion, but also enables volumetric OCT for comprehensive structural analysis and OCT angiography (OCTA) for visualizing vasculature. We demonstrate SS-OCT with a 325 kHz A-scan rate, 12.2 µm axial resolution (in air), and 15.5 mm depth range (in air) at 1310 nm wavelength. Advances in vertical-cavity surface-emitting laser (VCSEL) light sources, signal processing, optics and mechanical designs, enable a unique combination of high speed, long range, and deep penetration that addresses the challenges of anterior eye imaging. ![]() This study reports the development of prototype swept-source optical coherence tomography (SS-OCT) technology for imaging the anterior eye.
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