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Optical Coherence Tomographic Imaging of Posterior Episclera and Tenon’S Capsule

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Optical Coherence Tomographic Imaging of Posterior Episclera and Tenon’S Capsule Retina Optical Coherence Tomographic Imaging of Posterior Episclera and Tenon’s Capsule Kyoko Ohno-Matsui,1 Yuxin Fang,1 Kei Morohoshi,1 and Jost B. Jonas2 1Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, Tokyo, Japan 2Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany Correspondence: Kyoko Ohno-Mat- PURPOSE. To investigate structural features of the posterior episclera and Tenon’s capsule in sui, Department of Ophthalmology patients with high myopia. and Visual Science, Tokyo Medical and Dental University, 1-5-45 Yush- METHODS. This hospital-based observational study included highly myopic eyes (myopic ima, Bunkyo-ku, Tokyo 1138510, refractive error > À8 diopters or axial length ‡26.5 mm) in which the posterior sclera in its Japan; full thickness could be visualized on swept-source optical coherence tomography (OCT) [email protected]. images in all 12 radial scans centered on the fovea. We assessed the posterior episclera and Submitted: December 28, 2016 Tenon’s capsule. Accepted: May 29, 2017 RESULTS. The study included 278 eyes of 175 patients (mean age, 60.9 6 11.4 years; range, 32– Citation: Ohno-Matsui K, Fang Y, 89 years; axial length, 30.7 6 1.9 mm; range, 26.5–36.6 mm). The episclera was detected Morohoshi K, Jonas JB. Optical co- outside of the sclera in 164 eyes (59.0%) and appeared as a relatively uniform structure with a herence tomographic imaging of pos- reflectivity slightly lower than scleral reflectivity. In these eyes, mean scleral thickness was terior episclera and Tenon’s capsule. 197 6 73 lm in the foveal region and 164 6 64 lm and 146 6 59 lm at 1000 and 2500 lm Invest Ophthalmol Vis Sci. temporal to the fovea, respectively. The posterior episclera was visualized in the region 2017;58:3389–3394. DOI:10.1167/ temporal to the fovea. Mean episcleral thickness detected in 77 eyes was 80 6 27 lm and 82 iovs.16-21394 6 30 lm at 1000 lm and 2500 lm 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 6 32 lm. In 25 eyes with extremely thin sclera (<100 lm at 1000 lm temporal to the foveola), the mean thickness of the sclera and episclera were 87 6 11 lm and 65 6 15 lm, 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. Keywords: posterior episclera, Tenon’s capsule, optical coherence tomography, swept-source optical coherence tomography, pathologic myopia, high myopia he sclera, which is the outermost coat of the eye globe, is enhanced-depth imaging mode of OCT to examine the T mostly collagenous and can be divided into three layers: the posterior sclera and was able to determine the entire scleral episclera on the outer scleral surface, the scleral stroma, and thickness in the macular region in 48 eyes with high axial the lamina fusca on the inner surface of the sclera.1 Although myopia. Using swept-source OCT as a further refinement of the the episclera merges with the sclera, both tissues differ. The OCT technology, we observed the full posterior sclera in a collagen bundles in the episclera, compared to the collagen previous study of 278 eyes with high myopia.4 Although the bundles in the sclera, are thinner, more irregularly arranged, latter study briefly mentioned that the tissues exterior to the and less densely packed.2 The episclera also contains more sclera were detected in the OCT images of some eyes, a detailed ground substance than the sclera.2 The Tenon’s capsule is analysis of the posterior episclera and Tenon’s capsule was not composed of collagen and overlies the episclera.1,2 Histologic performed. Thus, the purpose of the present swept-source OCT studies revealed that the Tenon’s capsule is closely connected study was to perform a further analysis of collected images, to the outer episclera by delicate lamellae in the region of the with a focus on the features of the episclera and Tenon’s insertion of the extraocular muscles and with the dura mater capsule in the posterior segment of eyes with high myopia. around the optic nerve head.2 Observations of the episclera and Tenon’s capsule posterior to the equator have so far been limited mostly to surgical METHODS situations (e.g., during scleral buckling surgery for retinal detachment or ocular enucleation). Histologic studies have This observational hospital-based case series included patients rarely been focused on the posterior episclera or Tenon’s with high myopia who had consecutively been examined by capsule. swept-source OCT (DRI-OCT Atlantis; Topcon Corp., Tokyo, The clinical introduction of optical coherence tomography Japan) in the High Myopia Clinic at the Tokyo Medical and (OCT) has made it possible to visualize the posterior ocular Dental University between May 2014 and December 2015. The segment including the sclera. Imamura et al.3 used the Ethics Committee of the Tokyo Medical and Dental University Copyright 2017 The Authors iovs.arvojournals.org j ISSN: 1552-5783 3389 This work is licensed under a Creative Commons Attribution 4.0 International License. Downloaded from iovs.arvojournals.org on 10/04/2019 Imaging of Posterior Episclera and Tenon’s Capsule IOVS j July 2017 j Vol. 58 j No. 9 j 3390 standardized regression coefficient b, the nonstandardized regression coefficient b and its 95% confidence intervals (CI). Additionally, we carried out a 1-way ANOVA to compare the measurements obtained at different locations in the same eye. All P-values were two-sided and considered to be statistically significant if their value was lower than 0.05. RESULTS Out of 488 highly myopic eyes, which had undergone swept- FIGURE 1. Methods used to measure the thickness of the sclera, source OCT examination in the study period, the entire sclera episclera, and Tenon’s capsule. The thickness was measured along the was visualized in all 12 radial foveal scans in 278 eyes (57.0%) perpendicular axis to the curvature of the retinal pigment epithelium. of 175 patients.4 The mean age of these 175 patients was 60.9 Double-headed red arrow: sclera. Blue bar: episclera. Yellow bar: Tenon’s capsule. Note: Cross-section of an intrascleral blood vessel 6 11.4 years (32–89 years) and the mean axial length of the surrounded by loose tissue. The sclera appears thickened in that 278 eyes was 30.7 6 1.9 mm (26.5–36.6 mm). Among the 278 region. The choroid is barely detectable except for a few large vessels. eyes, the episclera and/or Tenon’s capsule were detected in 164 eyes (59.0%; or 33.6% of the original 488 eyes) of 117 patients (mean age: 59.4 6 11.4 years; mean axial length: 30.9 approved the investigation and confirmed that the methods 6 1.8 mm). The episclera appeared as a relatively uniform used in our study conformed to the tenets of the Declaration of structure with a reflectivity that was slightly lower than the Helsinki. The ethics committee waived informed consent, scleral reflectivity (Fig. 2). The episclera was closely attached since this study involved a reevaluation of images collected in to the outer surface of the sclera in most areas; although in our previously approved study, and since the previously some regions, especially in the macular area, the episclera was collected data were deidentified. High myopia was defined as clearly separated from the outer surface of the sclera (Figs. 3, a myopic refractive error (spherical equivalent) of > À8 4). The latter finding suggested that the episclera represented a diopters or an axial length ‡26.5 mm. Exclusion criteria were a different tissue, distinct from the sclera proper. The border lack of clear OCT images, and a history of previous vitreoretinal between the sclera and episclera was relatively clear in most surgery, since it could have affected the scleral curvature. eyes due to differences in reflectivity between these tissues. All patients underwent a comprehensive ophthalmologic Eyes with detectable episclera compared to eyes in which the examination including refraction, ocular biometry for mea- episclera was not visible had a significantly longer axial length surement of axial length (IOLMaster; Carl Zeiss Meditec Co., (P ¼ 0.003); thinner central retinal thickness (P ¼ 0.01); and Jena, Germany); color fundus photography; fundus autofluo- thinner subfoveal scleral thickness (P < 0.001). There were no rescence; and swept-source OCT. The optical coherence significant differences in age between these groups (P ¼ 0.66). tomography examination was carried out using a prototype Because the subfoveal choroid was too thin to be measured in of a swept-source OCT device (Topcon Corp.). This device had most eyes included in our study, choroidal thickness was not an A-scan repetition rate of 100,000 Hz. The light source used included in the list of outcome parameters. was a wavelength-sweeping laser centered at 1050 nm with a Overlying the episclera, the tissue considered to be Tenon’s bandwidth of approximately 100 nm. The effective bandwidth capsule was detected in 11 of the 278 eyes (4.0%). Tenon’s was roughly 60 nm due to water absorption. The axial capsule appeared as loosely arranged tissue. In some eyes, a resolution in the tissue was estimated to be 8 lm while the thin space was observed between the episclera and Tenon’s lateral resolution was estimated as 20 lm.
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