Yamada N, Emond M J, Mills R P, Leen M M, Chen P P, Stanford D C
Department of Ophthalmology, University of Washington, Seattle 98195-6485, USA.
J Glaucoma. 1998 Dec;7(6):378-87.
To test whether a statistical method using a probability map could detect true changes in optic disc topography.
The average of three Glaucoma-Scope images (Ophthalmic Imaging Systems were used for analysis at each of two sessions. A Glaucoma-Scope probability map was constructed for each eye using statistical methods. The proportion of topographic locations with p values less than 0.05 on a modified two-sample t test (p-proportion) and the difference in the mean position of the disc (MPD) from two imaging sessions were calculated. Two pairs of stereoscopic disc photographs for 43 eyes with longitudinal follow-up were evaluated for change by four experienced glaucoma specialists masked to patient clinical information. Clinical change was considered to have occurred when the assessments of at least three of the four specialists were agreed on. The cutoff values for p-proportion and change in MPD that provided 95% specificity were calculated using a separate sample of 69 subjects who had serial images taken at two separate sessions on the same day, and thus showed no clinical change in the optic disc.
The cutoff values of 95% specificity for the p-proportion and the change in MPD were 18% and 25.1 microns, respectively. Of 43 eyes with longitudinal follow-up, 14 showed definite clinical change. Sensitivity of the p-proportion and change in MPD for detecting this change was 100% and 85.7%, respectively. For all 43 patients with longitudinal follow-up, the percent change in intraocular pressure (IOP) correlated strongly with both the p-proportion and the change in MPD.
Using data obtained with the Glaucoma-Scope, a statistical method based on probability mapping can be used to detect true changes in disc topography. The p-proportion was more sensitive than change in MPD in detecting clinical change in the study eyes. This statistical methodology may also be applicable for interpretation of data obtained with other optic disc analyzers.
测试一种使用概率图的统计方法能否检测视盘地形图的真实变化。
在两个时间段分别使用青光眼视野仪（Ophthalmic Imaging Systems）进行分析，获取三只青光眼视野仪图像的平均值。使用统计方法为每只眼睛构建青光眼视野仪概率图。计算在改良双样本t检验中p值小于0.05的地形位置比例（p比例）以及两次成像检查中视盘平均位置（MPD）的差异。由四位经验丰富的青光眼专家对43只接受纵向随访的眼睛的两对立体视盘照片进行评估，专家对患者临床信息保密。当四位专家中至少三位达成一致评估意见时，认为发生了临床变化。使用69名在同一天的两个不同时间段拍摄了系列图像、因此视盘无临床变化的受试者的单独样本，计算出具有95%特异性的p比例和MPD变化的临界值。
p比例和MPD变化的95%特异性临界值分别为18%和25.1微米。在43只接受纵向随访的眼睛中，14只显示出明确的临床变化。p比例和MPD变化检测这种变化的敏感性分别为100%和85.7%。对于所有43例接受纵向随访的患者，眼内压（IOP）的百分比变化与p比例和MPD变化均密切相关。
利用青光眼视野仪获得的数据，基于概率图的统计方法可用于检测视盘地形图的真实变化。在检测研究眼中的临床变化时，p比例比MPD变化更敏感。这种统计方法也可能适用于解释其他视盘分析仪获得的数据。
