Supplementary Material for: Reference Database of Inner Retinal Layer Thickness and Thickness Asymmetry In Healthy Thai Adults as Measured by The Spectralis Spectral-Domain Optical Coherence Tomography

Purpose: To determine a reference database of the thickness and intraocular thickness asymmetry of total retina, retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) in healthy Thai subjects measured by the Spectralis spectral-domain optical coherence tomography Methods: This cross-sectional study recruited the healthy subjects age ≥18 years, having spherical refraction within ±6 diopters and cylindrical refraction ±3 diopters, from a hospital’s personnel and the people accompanying patients visiting the ophthalmology department. If the eligibility criteria were met for both eyes, only 1 eye of each subject was randomly selected for an analysis. Macular images were obtained using posterior pole thickness scan protocol over a 24x24 degree area at the center of the fovea. The automated retinal thickness segmentation values of total retina and three inner retinal layers were calculated for the mean and the mean intraocular thickness difference between superior and inferior retinal hemispheres. The influence of age, gender, and axial length on thickness and thickness asymmetry of individualized retinal layer were evaluated. Results: Two hundred and fifty-two subjects were included in study with a mean (SD) age of 46.7 (15.8) years and 120 (47.6%) were males. According to the Early Treatment Diabetic Retinopathy Study map, the inner ring area was the thickest location of the total retina (range; 326.0 to 341.5 µm), ganglion cell layer (range; 47.7 to 52.7 µm), and inner plexiform layer (range; 39.9 to 42.1 µm); whereas the thickest location of RNFL was at the outer ring area (range; 18.8 to 47.5 µm). For posterior pole intraocular thickness asymmetry, the greatest mean ± SD difference was observed for total retina (9.0 ± 2.2 µm), followed by RNFL (9.9 ± 3.2 µm), and GCL (2.7 ± 0.6 µm) and the lowest mean difference was noted for IPL (2.4 ± 0.5 µm). The thickness and thickness asymmetry of each retinal layer were variably influenced by age, gender, and axial length; however, these factors had a minimal influence on the thickness asymmetry maps of GCL and RNFL. Conclusion: The reference database of the macular thickness and thickness asymmetry from this study would be beneficial in determining physiologic variations of the OCT parameters in the healthy Thai population.

【研究目的】本研究旨在利用Spectralis光谱域光学相干断层扫描（Spectralis spectral-domain optical coherence tomography），建立健康泰国受试者的视网膜总厚度、视网膜神经纤维层（retinal nerve fiber layer, RNFL）、神经节细胞层（ganglion cell layer, GCL）及内丛状层（inner plexiform layer, IPL）的厚度及眼内厚度不对称性参考数据库。
【研究方法】本研究为横断面研究，招募年龄≥18岁、球镜屈光度数范围为±6屈光度、柱镜屈光度数范围为±3屈光度的健康受试者，招募来源为医院工作人员及眼科门诊陪诊人员。若受试者双眼均符合纳入标准，则随机选取单眼纳入分析。采用后极部厚度扫描方案，于黄斑中心凹区域采集24°×24°范围的黄斑图像。计算视网膜总厚度及三层视网膜内层的自动分割厚度值，包括平均厚度值及视网膜上、下半球间的平均眼内厚度差。评估年龄、性别及眼轴长度对各视网膜层厚度及厚度不对称性的影响。
【研究结果】本研究共纳入252名受试者，平均年龄（标准差）为46.7（15.8）岁，其中男性120名（占比47.6%）。根据早期糖尿病视网膜病变治疗研究（Early Treatment Diabetic Retinopathy Study, ETDRS）图谱，视网膜总厚度、神经节细胞层及内丛状层的最厚位点均位于内环区域（范围分别为326.0~341.5 μm、47.7~52.7 μm、39.9~42.1 μm）；而视网膜神经纤维层的最厚位点则位于外环区域（范围18.8~47.5 μm）。在后极部眼内厚度不对称性方面，平均差值最高的为视网膜总厚度（9.0±2.2 μm），其次为视网膜神经纤维层（9.9±3.2 μm）、神经节细胞层（2.7±0.6 μm），最低的为内丛状层（2.4±0.5 μm）。各视网膜层的厚度及厚度不对称性均受年龄、性别及眼轴长度的不同程度影响；但上述因素对神经节细胞层及视网膜神经纤维层的厚度不对称性图谱影响较小。
【研究结论】本研究建立的黄斑厚度及厚度不对称性参考数据库，可为明确健康泰国人群光学相干断层扫描（OCT）参数的生理变异范围提供重要参考依据。