Purpose: To investigate structural features of the posterior episclera and Tenon's capsule in patients with high myopia.
Methods: 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.
Results: 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.
Conclusions: 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.