Purpose: To provide a geographical map of choroidal thickness (CT) around the macular region among subjects with low, moderate and high myopia. Methods: 20 myopic subjects (n = 40 eyes) without other identified pathologies participated in this study: 20 eyes of ≤ 3 diopters (D) (low myopic), 10 eyes between -3 and -6D (moderate myopic), and 10 eyes of ≥ 6D (high myopic). The mean age of subjects was 30.2 years (± 7.6 years; range, 24 to 46 years). A 1050 nm spectral-domain optical coherence tomography (SD-OCT) system, operating at 120 kHz imaging rate, was used in this study to simultaneously capture 3D anatomical images of the choroid and measure intraocular length (IOL) in the subject. The 3D OCT images of the choroid were segmented into superior, inferior, nasal and temporal quadrants, from which the CT was measured, representing radial distance between the outer retinal pigment epithelium (RPE) layer and inner scleral border. Measurements were made within concentric regions centered at fovea centralis, extended to 5 mm away from fovea at 1 mm intervals in the nasal and temporal directions. The measured IOL was the distance from the anterior cornea surface to the RPE in alignment along the optical axis of the eye. Statistical analysis was performed to evaluate CT at each geographic region and observe the relationship between CT and the degree of myopia. Results: For low myopic eyes, the IOL was measured at 24.619 ± 0.016 mm. The CT (273.85 ± 49.01 μm) was greatest under fovea as is in the case of healthy eyes. Peripheral to the fovea, the mean CT decreased rapidly along the nasal direction, reaching a minimum of 180.65 ± 58.25μm at 5 mm away from the fovea. There was less of a change in thickness from the fovea in the temporal direction reaching a minimum of 234.25 ± 42.27 μm. In contrast to the low myopic eyes, for moderate and high myopic eyes, CTs were thickest in temporal region (where CT = 194.94 ± 27.28 and 163 ± 34.89 μm, respectively). Like the low myopic eyes, moderate and high myopic eyes had thinnest CTs in the nasal region (where CT = 100.84 ± 16.75 and 86.64 ± 42.6μm, respectively). High myopic eyes had the longest mean IOL (25.983 ± 0.021mm), while the IOL of moderate myopia was 25.413 ± 0.022 mm (**p < 0.001). The CT reduction rate was calculated at 31.28 μm/D (diopter) from low to moderate myopia, whilst it is 13.49 μm/D from moderate to high myopia. The similar tendency was found for the IOL reduction rate in our study: 0.265 mm/D from low to moderate myopia, and 0.137 mm/D from moderate to high myopia. Conclusion: The CT decreases and the IOL increases gradually with the increase of myopic condition. The current results support the theory that choroidal abnormality may play an important role in the pathogenesis of myopic degeneration.

中文翻译：

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使用 1050 nm 光谱域光学相干断层扫描对近视眼脉络膜厚度进行地理测绘

目的：提供低度、中度和高度近视受试者黄斑区脉络膜厚度（CT）的地理分布图。方法：20 名无其他已确定病理的近视受试者（n = 40 只眼）参与了本研究：20 只眼≤3 屈光度 (D)（低度近视），10 只眼在 -3 和 -6D 之间（中度近视），10 只眼≥ 6D（高度近视）。受试者的平均年龄为 30.2 岁（± 7.6 岁；范围为 24 至 46 岁）。本研究中使用了 1050 nm 光谱域光学相干断层扫描 (SD-OCT) 系统，以 120 kHz 的成像速率运行，以同时捕获脉络膜的 3D 解剖图像并测量受试者的眼内长度 (IOL)。脉络膜的 3D OCT 图像被分割为上、下、鼻和颞象限，从中测量 CT，表示外视网膜色素上皮 (RPE) 层和内巩膜边界之间的径向距离。在以中央凹为中心的同心区域内进行测量，在鼻和颞方向上以 1 mm 的间隔延伸到距中央凹 5 mm 的位置。测量的 IOL 是从角膜前表面到沿眼睛光轴对齐的 RPE 的距离。对各地理区域的CT进行统计分析，观察CT与近视度数的关系。结果：对于低度近视眼，IOL 测量值为 24.619 ± 0.016 mm。CT (273.85 ± 49.01 μm) 在中央凹下最大，在健康眼睛的情况下也是如此。中央凹周边，平均CT沿鼻方向迅速下降，在距中央凹5 mm处最小达到180.65±58.25μm。中央凹在时间方向上的厚度变化较小，达到最小值 234.25 ± 42.27 μm。与低度近视眼相比，对于中度和高度近视眼，颞区 CT 最厚（CT 分别为 194.94 ± 27.28 和 163 ± 34.89 μm）。与低度近视眼一样，中度近视眼和高度近视眼的鼻部 CT 最薄（CT 分别为 100.84 ± 16.75 和 86.64 ± 42.6 μm）。高度近视眼的平均 IOL 最长 (25.983 ± 0.021mm)，而中度近视的 IOL 为 25.413 ± 0.022 mm (**p < 0.001)。CT 缩小率从低度到中度近视计算为 31.28 μm/D（屈光度），而从中度到高度近视为 13.49 μm/D。在我们的研究中，IOL 减少率也发现了类似的趋势：从低度到中度近视为 0.265 mm/D，0.265 mm/D。137 mm/D 从中度到高度近视。结论：随着近视程度的加重，CT逐渐减小，IOL逐渐增大。目前的结果支持脉络膜异常可能在近视变性的发病机制中起重要作用的理论。