In vivo megahertz A-scan rate ophthalmic robotically aligned optical coherence tomography

Abstract

Purpose : Robotically aligned OCT (RAOCT) was recently introduced for ophthalmic imaging but was previously limited to single targets of interest with fixed A-scan rates and imaging depths. Here we demonstrate in vivo imaging using a flexible RAOCT platform that adapts to image the target tissue of interest.

Methods : Our modular OCT imaging platform consists of a scan head and interchangeable modules wherein the total mass of the scan head and a given imaging module was under the robot mass limit (Universal Robots, UR5e, 5 kg, Fig. 1A). Externally mounted face tracking cameras provide gross positional information (Fig. 1B) and module integrated pupil tracking cameras (Fig. 1C) provide high accuracy positional information (Fig. 1D). A given module includes OCT imaging optics, integrated pupil cameras, and pupil illumination. We designed the cornea module with a field-of-view (FOV) of 16 mm while the retinal module expands RAOCT to beyond 40° FOV. Our swept-source OCT engine utilizes a custom VCSEL with electronically switchable A-scan rate and MZI lengths (Thorlabs; λ₀ = 1045nm; 250, 500 kHz, 1 MHz; 12, 6, 3 mm imaging depths). To date, we have imaged 4 healthy volunteers with this system under an IRB approved protocol at the Duke Eye Center.

Results : We measured lateral and axial tracking accuracy to be <11µm and precision to be <±5µm for both modules (Fig. 1D). Fig. 2 demonstrates in vivo volumetric imaging of the front and back of the eye with our system. Fig. 2A shows a full view of the anterior chamber utilizing 12 mm, 250 kHz A-scan imaging. Fig. 2B demonstrates 3 mm depth, 1 MHz retinal imaging of a healthy volunteer.

Conclusions : We demonstrate megahertz A-scan rate, robotically aligned OCT imaging in healthy volunteers. This 5-10x speed improvement over previous ophthalmic RAOCT systems can enable new imaging options, including angiography.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Interchangeable Module Tracking Performance. A) Non-tracking camera photograph of cornea module B) Face tracking camera views C) Pupil tracking camera views D) Lateral and axial tracking accuracy and precision for cornea and retina imaging modules.

 

RAOCT Imaging A) 250 kHz A-scan imaging (12mm depth) with cornea module. Left, volumetric rendering of anterior chamber and eye lashes. Right, registered and averaged B-scan. B) 1 MHz A-scan imaging (3mm depth) with retinal module. Left, registered and averaged B-scan centered at fovea. Right, volumetric rendering of retina.