Association between shape of sclera and myopic retinochoroidal lesions in patients with pathologic myopia.

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.

Quantitative analyses of high-resolution 3D MR images of highly myopic eyes to determine their shapes.

PURPOSE: We analyzed the symmetry and pointedness of the posterior segment of highly myopic eyes. METHODS: We studied 234 eyes of 117 patients with bilateral high myopia (refractive error ≤-8.00 diopters [D]) and 40 eyes of 20 patients with emmetropia (refractive error between -1.0 and +1.0 D). Volume renderings of high-resolution magnetic resonance (MR) images were performed to obtain 3D images of the eye. To analyze the symmetry and pointedness of the posterior surface, a software was developed to measure the area and angle of a fan-shaped segment formed by selected points on the MR images. RESULTS: All of the emmetropic eyes were symmetrical in the horizontal and sagittal planes with no deformity. In highly myopic eyes, the shape was symmetrical in the horizontal plane in 146 eyes (62.4%) and in the sagittal plane in 162 (69.2%). The shape of the posterior pole was pointed (angle of fan-shaped segment <150°) in 45.7% and blunted (angle ≥150°) in 54.3% of highly myopic eyes. The most common shape was symmetrical in the horizontal and sagittal planes, and the posterior surface was blunt. The shape of the two eyes of the same individual was the same in 61 of 117 patients (52.1%). In 56 patients whose two eyes had different shapes, the most frequent pattern was a difference in the pointedness (51.8%). CONCLUSIONS: Quantitative assessments of the shape of eyes were useful in determining the pattern of eye shape deformity specific to pathologic myopia.