Optical Coherence Tomographic Imaging of Posterior Episclera and Tenon's Capsule

To investigate structural features of the posterior episclera and Tenon's capsule in patients with high myopia.

This hospital-based observational study included highly myopic eyes (myopic refractive error > -8 diopters or axial length ≥26.5 mm) in which the posterior sclera in its full thickness could be visualized on swept-source optical coherence tomography (OCT) images in all 12 radial scans centered on the fovea. We assessed the posterior episclera and Tenon's capsule.

The study included 278 eyes of 175 patients (mean age, 60.9 ± 11.4 years; range, 32-89 years; axial length, 30.7 ± 1.9 mm; range, 26.5-36.6 mm). The episclera was detected outside of the sclera in 164 eyes (59.0%) and appeared as a relatively uniform structure with a reflectivity slightly lower than scleral reflectivity. In these eyes, mean scleral thickness was 197 ± 73 μm in the foveal region and 164 ± 64 μm and 146 ± 59 μm at 1000 and 2500 μm temporal to the fovea, respectively. The posterior episclera was visualized in the region temporal to the fovea. Mean episcleral thickness detected in 77 eyes was 80 ± 27 μm and 82 ± 30 μm at 1000 μm and 2500 μm temporal to the fovea, respectively. Tenon's capsule was detected in 11 of the 278 eyes (4.0%) as structurally, loosely connected tissue with a meshwork-like appearance. The measured thickness in four eyes was 60 ± 32 μm. In 25 eyes with extremely thin sclera (<100 μm at 1000 μm temporal to the foveola), the mean thickness of the sclera and episclera were 87 ± 11 μm and 65 ± 15 μm, respectively.

Swept-source OCT applied to a subset of highly myopic eyes with significant thinning of the retina and choroid allowed visualization of the posterior sclera and episclera, and in some cases, also Tenon's capsule.