Whorl-Like Collagen Fiber Arrangement Around Emissary Canals in the Posterior Sclera.

Abstract

Purpose: To investigate the collagen fiber arrangement around emissary canals in the posterior sclera.

Methods: One hundred sixty-five eyes of 93 patients who underwent polarization-sensitive optical coherence tomography (PS-OCT) examinations in 2019 in the Institute of Science Tokyo were studied. Multimodal imaging, including streamline images derived from PS-OCT data, B-scan images, and indocyanine green angiography (ICGA) images, was used to investigate the collagen fiber arrangement around emissary canals and scleral pits in vivo. Additionally, the collagen fiber arrangement around the emissary canals in porcine sclera was examined using scanning electron microscopy and light microscopy.

Results: Streamline images showed whorl-like collagen fiber arrangements on all eyes, and 25 eyes were selected for the analysis. All whorls corresponded to emissary canals on B-scan images. The whorls were confirmed to correspond to the posterior ciliary artery entries in three eyes and posterior vortex vein exits in three eyes with available ICGA images. Streamline cutaway images showed that the whorls surrounded the emissary canals throughout the entire course. In 16 eyes with 20 scleral pits, whorls were seen surrounding all the pits. Microscopic study using porcine sclera confirmed the whorl-like structures around the emissary canals ex vivo and demonstrated tangentially arranged collagen fiber bundles forming the circle.

Conclusions: The collagen fibers are arranged as whorl-like structures around the vessel emissary canals in the posterior sclera, which is a knowledge gap for basic scleral histology. Additionally, this study demonstrated a strong correlation between PS-OCT findings and microscopic histology, underscoring PS-OCT's utility in detecting scleral collagen fiber arrangements.