Wide-field whole eye optical coherence tomography with ocular pupil tracking

Abstract

Purpose : Changes in posterior eye shape can occur in conditions like high intracranial pressure and myopia. Most eye shape studies use magnetic resonance imaging (MRI), which is logistically challenging for routine eye use. Whole eye optical coherence tomography (OCT) is an appealing alternative due to its higher resolution and ease for multiple imaging sessions. We have previously shown accurate posterior eye curvature estimates using whole eye OCT compared to MRI. Here, we build on previous work using a system with a switch-based, linear polarization multiplexed sample arm to maximize power to each path, increase acquisition speed, limit motion artifacts, and add a pair of tracking cameras to triangulate pupil position during the scan.

Methods : Conventional OCT can only image either the anterior or posterior eye due to the cornea and lens’ refractive power. Using polarization multiplexing to create anterior and posterior imaging paths, we can image both the anterior chamber and retina. Depth separation was previously accomplished using coherence revival, but led to sample power splitting between imaging paths. Here, we utilize a galvo switch to image the anterior and retina in alternating B-scans (Fig. 1). Additionally, we incorporated pupil-tracking cameras to estimate patient motion during imaging. We imaged a healthy volunteer with this system under an IRB approved protocol at the Duke Eye Center.

Results : Averaged B-scans of interlaced anterior and retina volumes are shown in Fig. 2. We achieved an imaging depth of 8 mm at a rate of 400k A-scans per second. Additionally, our tracking cameras estimated patient motion during imaging (Fig. 2).

Conclusions : We demonstrated a swept-source OCT system capable of high-speed interlaced acquisition of both the anterior chamber and retina. Integrated pupil-tracking cameras enable estimates of 3D eye motion during imaging which offers the potential for post-processing motion artifact correction.

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

 

OCT engine and sample arm schematics and photo of OCT scan head. LP: Linear Polarizer ETL: Electric Tunable Lens, HWP: Half Wave Plate.

 

Registered and averaged B-scan of a) anterior chamber and b) retina acquired concurrently. A non-optical fixed frequency artifact is in these images, which will be removed with refinement of acquisition code. Summed voxel projection of c) anterior segment, d) retina. e) Estimated subject motion, total motion was less than 0.5 mm due to head stabilization.