Stereoscopic Analysis of Optic Nerve Head Parameters in Primary Open Angle Glaucoma: The Glaucoma Stereo Analysis Study

Purpose
The Glaucoma Stereo Analysis Study (GSAS), a cross sectional multicenter collaborative study, used a stereo fundus camera to assess various morphological parameters of the optic nerve head (ONH) in glaucoma patients and investigated the relationships between these parameters and patient characteristics.
Subjects and Methods
The study included 187 eyes of 187 subjects with primary open angle glaucoma or normal tension glaucoma (male: female  = 100: 87, age  = 61±9 years). Stereo pairs of ONH photographs were made with a stereo fundus camera (nonmyd WX). ONH morphological parameters were calculated with prototype analysis software. In addition to 35 standard parameters, we defined three novel parameters: disc tilt angle, rim decentering, and the absolute value of rim decentering. The correlation between each parameter and patient characteristics was analyzed with Spearman's rank correlation coefficient.
Results
Patient characteristics included refractive error of −3.38±3.75 diopters, intraocular pressure (IOP) of 13.6±2.6 mmHg, and visual field mean deviation (MD) of −4.71±3.26 dB. Representative ONH parameters included a horizontal disc width of 1.66±0.28 mm, vertical disc width of 1.86±0.23 mm, disc area of 2.42±0.63 mm2, cup area of 1.45±0.57 mm2, and cup volume of 0.31±0.22 mm3. Correlation analysis revealed significant negative associations between vertical cup-to-disc ratio (0.82±0.08) and MD (r = −0.40, P<0.01) and between disc tilt angle (10.5±12.5 degrees) and refractive error (r = −0.36, P<0.01). Seventy-five percent of the eyes had a positive value for rim decentering (0.30±0.42), indicating that rim thinning manifested more often as an inferior lesion than a superior lesion.
Conclusion
We used stereoscopic analysis to establish a database of ONH parameters, which may facilitate future studies of glaucomatous changes in ONH morphology.

研究目的
青光眼立体分析研究（Glaucoma Stereo Analysis Study, GSAS）是一项横断面多中心协作研究，采用立体眼底相机对青光眼患者的视神经乳头（optic nerve head, ONH）各项形态学参数进行评估，并探究这些参数与患者临床特征之间的关联。

研究对象与方法
本研究共纳入187名受试者的187只患眼，均为原发性开角型青光眼或正常眼压性青光眼患者，其中男女性别比为100:87，年龄为61±9岁。研究采用nonmyd WX立体眼底相机采集视神经乳头立体影像对；通过原型分析软件计算视神经乳头形态学参数。除35项标准参数外，本研究还定义了三项全新参数：视盘倾斜角、视盘边缘偏心度以及视盘边缘偏心度的绝对值。采用斯皮尔曼秩相关系数（Spearman's rank correlation coefficient）分析各项参数与患者临床特征之间的相关性。

研究结果
受试者的临床特征包括：屈光不正为-3.38±3.75屈光度，眼内压（intraocular pressure, IOP）为13.6±2.6 mmHg，视野平均偏差（visual field mean deviation, MD）为-4.71±3.26 dB。代表性视神经乳头参数包括：视盘水平径为1.66±0.28 mm，视盘垂直径为1.86±0.23 mm，视盘面积为2.42±0.63 mm²，视杯面积为1.45±0.57 mm²，视杯体积为0.31±0.22 mm³。相关性分析显示，垂直杯盘比（0.82±0.08）与视野平均偏差呈显著负相关（r=-0.40, P<0.01），视盘倾斜角（10.5±12.5°）与屈光不正亦呈显著负相关（r=-0.36, P<0.01）。75%的患眼视盘边缘偏心度为正值（0.30±0.42），提示视盘边缘变薄更多表现为下方病变而非上方病变。

研究结论
本研究通过立体分析构建了视神经乳头形态学参数数据库，可为未来视神经乳头形态学青光眼病变相关研究提供支持。