Visibility of the sclera in highly myopic eyes measured by polarization-sensitive optical coherence tomography

Abstract

Purpose : The tissue properties of the sclera in highly myopic eyes remain unknown. Although recent techniques of polarization-sensitive optical coherence tomography (PS-OCT) to measure the depth-resolved birefringence of the sclera in vivo may open new opportunities, it is challenging to measure full thickness of the sclera. The purpose of this study is to investigate the visibility of the sclera in highly myopic eyes measured by PS-OCT.

Methods : We measured 98 human subjects of highly myopic eyes that included pathologic myopia using a prototype of PS-OCT in vivo, which had a center wavelength of 1,060 µm and 100 kHz A-scan rate of a frequency-swept laser. The fundus was scanned with a raster scan of 9 mm × 9 mm to include the optic nerve head (ONH) and the macula. Visibility of the posterior boundary of the sclera under the fovea was evaluated using the OCT intensity images of PS-OCT by a single grader. The data that showed unsuccessful PS-OCT measurement were excluded from the evaluation.

Results : The 145 eyes of the 85 subjects met the inclusion criteria for the evaluation. The posterior boundary of the sclera under the fovea was visible in 111 eyes (77%). Figure 1 shows the PS-OCT images of pathologic myopia as an example that visualized full thickness of the sclera under the fovea. Polarimetric entropy image (C) showed depolarization by melanin at the retinal pigment epithelium and choroid. Local retardation (D) image showed low and highly birefringent layers at the upper and deeper regions of the sclera, respectively. Optic axis image (E) showed multiple layers that had different orientations in the sclera. Streamline rendering viewed from the inside of the retina (F) visualized a concentric pattern at the peripapillary region and radial pattern around it. The view from the outside of the retina (G) visualized that the concentric pattern around the ONH largely extended to posterior pole.

Conclusions : We observed full thickness of the sclera under the fovea with high success rate using PS-OCT. Fiber organization of the sclera measured by PS-OCT may provide new insights into future studies of pathologic myopia.

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

 

Figure 1. En face maximum intensity projection of OCT intensity (A), OCT intensity B-scan (B), and polarimetric contrasts (C)-(G) of the pathologic myopia.