Purpose: The purpose of the study was to analyze the shape of the sclera determined by swept-source optical coherence tomography (OCT) and to determine the relationship between the shape and the myopic retinochoroidal lesions.
Methods: We studied 488 eyes of 272 patients with high myopia (refractive error ≥-8.00 diopters [D] or axial length >26.5 mm) and 43 emmetropic eyes of 43 controls (refractive error ≤±3 D). An image of the sclera was obtained by a swept-source OCT prototype instrument that uses a wavelength sweeping laser centered on 1 μm wavelength with an A-scan repetition rate of 100,000 Hz. The scans were 12 mm radial scans centered on the fovea. Seventy eyes were also examined by three-dimensional magnetic resonance imaging (3D MRI) to obtain the contour of the outer surface of the eyes. The main outcome measures, visibility of the entire sclera layer, scleral thickness, scleral contour, and location of the most protruded point of the globe, were obtained by swept-source OCT and 3D MRI.
Results: The entire thickness of the sclera was observed in 278 of 488 (57.0%) highly myopic eyes, but the outer border was not observed in any of the emmetropic eyes. The mean subfoveal scleral thickness was 227.9 ± 82.0 μm in the highly myopic eyes. The sclera was thickest at 3000 μm nasal to the fovea. The curvatures of the inner scleral surface of highly myopic eyes could be divided into curvatures that sloped toward the optic nerve, those that were symmetrical and centered on the fovea, those that were asymmetrical, and those that were irregular. Patients with irregular curvature were significantly older and had significantly longer axial lengths than those with other curvatures. Myopic fundus lesions were present significantly more frequently in the eyes with irregular curvature. All of the eyes whose scleral curvature sloped toward the optic nerve had nasally distorted shape in the 3D MRI images, and all eyes with temporally dislocated shape had irregular curvature.
Conclusions: In vivo evaluations of the sclera in highly myopic eyes by swept-source OCT can provide important information on deformations of the sclera and how such deformities are related to myopic fundus lesions.