Birefringence derived artifact in OCT imaging of eyes with pathologic myopia and glaucoma

Abstract

Purpose : The sclera and lamina cribrosa exhibit birefringence because of dense collagen lamellae. This birefringence alters the polarization state of the incident light and induced artifact in conventional OCT images.We investigated birefringence-derived artifact in scleral OCT images in pathologic myopia and optic disc OCT images in glaucoma.

Methods : This study included 76 eyes of 42 patients with pathologic myopia and 44 eyes of 29 patients with glaucoma. A set of five B-scan images of the macula for pathologic myopia and optic disc for glaucoma were obtained using commercial 1.0μm swept-source OCT (Topcon DRI-OCT Triton). A dataset of prototype 1.0 μm swept-source polarization-diversity OCT images was used to identify polarization-dependent OCT images (i.e., complex averaging of OCT signals from two polarization channels) and polarization-independent OCT images (i.e., intensity averaging of two OCT signals). Polarization-dependent OCT images and commercial OCT images were assessed for the presence of birefringence-derived artifacts by comparison with polarization-independent OCT images.

Results : Both polarization-dependent OCT images and commercial OCT images contained birefringence derived artifacts. In the eyes with pathologic myopia, scleral vessel artifacts were present in 46 of 76 eyes (60.5%) imaged by polarization-dependent OCT and 17 of 76 eyes (22.4%) imaged by commercial OCT. The proportion of images that showed scleral vessel artifacts was significantly greater among polarization-dependent OCT images than among commercial OCT images (P < 0.001). In the eyes with glaucoma, 3 of 44 eye (6.8 %) showed birefringence derived artifacts look like lamina defect in both polarization-dependent OCT images and commercial OCT images.

Conclusions : Birefringence-derived artifacts were present in commercial OCT images. These artifacts might cause overestimation of scleral vessels and erroneous interpretation of the lamina cribrosa. In polarization-diversity OCT images, artifactual findings could easily be distinguished from real structures, hence, polarization-diversity OCT is an effective tool to evaluate pathologic myopia and glaucoma.

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

 

Scleral vessel artifacts in an eye with pathologic myopia (arrows).

 

Lamina defect artifact in an eye with glaucoma (arrows).