Objective: To investigate the ultrasonographic measurements of the optic nerve subarachnoid space (ONSAS) in patients with normal tension glaucoma (NTG). Methods: Cross-sectional study. Patients with NTG or primary open-angle glaucoma (POAG) but without any anti-glaucoma treatment and the control group were collected from June 2016 to March 2017 at Beijing Tongren Hospital affiliated to Capital Medical University. Measurements of 24-h intraocular pressure, central corneal thickness, mean visual field damage, visual axis, blood pressure and body mass index and ocular ultrasound scans were performed. The differences in the ONSAS of the two-dimensional ultrasound images of the three groups of subjects and their correlation with various clinical variables were evaluated. Qualitative data were analyzed by the chi-square test for comparison between groups; quantitative data were analyzed by the one-way ANOVA for comparison between groups, and the LSD-t test was used for comparison between groups; the Pearson correlation analysis was used for correlation analysis of measurement data. The intra-group correlation coefficient was used to evaluate the reproducibility and repeatability of two measurements by different measurers or the same measurer. Results: A total of 35 patients (35 eyes) with NTG were enrolled in the NTG group, including 14 males and 21 females, aged (50±8) years; 32 patients (32 eyes) with POAG were enrolled in the POAG group, including 14 males and 18 females, aged (52±10) years; 37 healthy people (37 eyes) were enrolled in the control group, including 20 males and 17 females, aged (49±9) years. The ONSAS was (5.07±0.83) mm(2) in the retrobulbar 3- to 7-mm range in the NTG group, significantly smaller than the control group (6.57±1.43) mm(2) and the POAG group (6.19±0.90) mm(2) (t=1.17, 1.29; P=0.03, 0.01). There was no significant difference in the statistical results between the control group and the POAG group (t=1.31, P=0.75). Between the ONSAS and mean intraocular pressure and maximum intraocular pressure, there was a statistically positive correlation in the NTG group (r=0.66, 0.48; both P<0.01), but there was no linear correlation; there was no statistical correlation in the control group or the POAG group (all P>0.05). There was no statistically significant association between the ONSAS and age, mean arterial pressure, body mass index, central corneal thickness, visual axis length, and mean visual field loss in any group (all P>0.05). Conclusion: Compared with the POAG group and the control group, the ONSAS is smaller in the NTG group, indicating lower retrobulbar cerebrospinal fluid pressure, and it is positively correlated with the mean intraocular pressure and the highest intraocular pressure. (Chin J Ophthalmol, 2018, 54: 827-832).
目的： 探讨正常眼压性青光眼（NTG）的视神经蛛网膜下腔面积（ONSASA）的特点及其相关因素。 方法： 横断面研究。收集自2016年6月至2017年3月在首都医科大学附属北京同仁医院北京同仁眼科中心就诊的明确诊断且未经任何抗青光眼治疗的NTG患者（NTG组）、原发性开角型青光眼（POAG）患者（POAG组）及自愿接受检查的健康人（对照组），进行24 h眼压、中央角膜厚度、平均视野损伤、视轴长度、血压、体质量指数测量并进行眼部超声扫描。测量分析3组受试人群二维超声图像的ONSASA的差异及其与各临床变量之间的相关性。定性资料应用χ(2)检验进行组间比较；定量资料应用单因素方差分析进行组间比较，组间两两比较应用LSD-t检验；计量资料的相关性分析采用Pearson相关分析方法。 结果： NTG组纳入NTG患者35例（35只眼），男性14例，女性21例，年龄（50±8）岁；POAG组纳入POAG患者32例（32只眼），男性14例，女性18例，年龄（52±10）岁；对照组37名（37只眼），男性20名，女性17名，年龄（49±9）岁。NTG组球后3~7 mm范围的ONSASA为（5.07±0.83）mm(2)，明显小于POAG组及对照组[（6.19±0.90）mm(2)、（6.57±1.43）mm(2)；t=1.29、1.17；P=0.01、0.03]；POAG组与对照组差异无统计学意义（t=1.31，P=0.75）。在NTG组ONSASA与平均眼压以及最高眼压均呈正相关关系（r=0.66，0.48；均P<0.01），但不存在线性相关；而在POAG组及对照组ONSASA与平均眼压以及最高眼压均无相关性（均P>0.05）。ONSASA与任何组中的年龄、平均动脉压、体质量指数、中心角膜厚度、视轴长度、平均视野缺失均无相关性（均P>0.05）。 结论： 与POAG患者和健康者相比，NTG患者的ONSASA较小，表明NTG患者球后受到的脑脊液压力较低，且其与平均眼压和最高眼压呈正相关。（中华眼科杂志，2018，54：827-832）.
Keywords: Glaucoma; Glaucoma, open-angle; Intraocular pressure; Optic nerve; Subarachnoid space; Ultrasonography.