Novel Simultaneous Nasal and Temporal Anterior Segment Imaging with OCT

Abstract

Purpose : Anterior segment (AS) swept source optical coherence tomography (SS-OCT) imaging can provide a means for obtaining Schlemm canal (SC) measurements which can be beneficial for both studying the effects of glaucoma therapies on the outflow facility as well as provide a noninvasive visualization technique for presurgical planning. Hence, a noncontact attachment was designed for perpendicular orientation scanning of the limbus region in order to provide an improved visualization of SC with a better reproducibility.

Methods : Attachment components consist of two 12.7 mm side mirrors and one 10 mm triangular prism, coated in protected gold. The mirrors were mounted onto a custom made aluminum breadboard via magnetic posts (Figure 1) to allow for a simple and quick alignment. Three 10 mm x 10 mm B-scans were captured, containing both nasal and temporal sides of the limbus, on a prototype SS-OCT device. In comparison, six 6 mm x 6 mm images were taken in the same eyes, in order to capture similar regions bilaterally utilizing PlexElite 9000 (Zeiss, Dublin, CA) with the add-on anterior segment lens. Images from both devices were processed utilizing ImageJ to maximize visualization of SC. The cross sectional area of SC was obtained by two masked graders manually segmenting the structures on a stack of 10 consecutive slices. The reproducibility of the two devices were assessed by within subject coefficient of variation (WSCoV).

Results : Four healthy individuals were scanned with both systems at the same session. Figure 2A demonstrates the capabilities of the novel system by orienting the limbus nearly flat, compared to the considerable angle that can be seen in Figure 2B using conventional imaging. Our preliminary results showed that the WSCoVs of SC average area between the measurements obtained with the novel system are 1-16% lower than those from the PlexElite (Table).

Conclusions : Our proof of concept study sucessfully demonstrates that our new system is able to acquire images perpendicular to the limbus and provides improved reproducibility of SC measurements compared to conventional antero-posterior scanning. Future stage of development will allow outflow system structures visualization of the entire circumferential angle.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.