Applegate R A, Bradley A, van Heuven W A, Lee B L, Garcia C A
Department of Ophthalmology, University of Texas, Health Science Center at San Antonio 78284-6230, USA.
Invest Ophthalmol Vis Sci. 1997 Apr;38(5):783-91.
Studies using optimized entoptic viewing of the parafoveal retinal vasculature have shown that normal subjects see their own capillaries with greater detail in the fovea than seen typically in fluorescein angiography. The authors have extended these investigations to persons with diabetes to evaluate the sensitivity, specificity, and accuracy with which they can detect and locate their own parafoveal retinal defects untrained.
A vascular entoptoscope using Maxwellian view optics creates a high-contrast entoptic view of retinal vasculature abnormalities in the parafoveal area. Using a double-masked protocol, 70 patients with diabetes and 29 control subjects described, drew, and quantified their entoptic image. These entoptic records were compared to angiograms and color photographs obtained immediately after the entoptic evaluation.
Angiograms or color photographs or both showed that 61 of 70 patients with diabetes had retinal defects (e.g., microaneurysms or exudates or both) within the field of view of the Vascular Entoptoscope (8.1 degrees or 11.6 degrees circular field depending on the Vascular Entoptoscope used: parafoveal area subtends approximately 9.7 degrees). Of these 61 patients with diabetes, 51% (31) observed dark "spots" or "blobs" in the entoptic field corresponding to retinal defects in the angiograms or photographs or both. Seven (18%) of the 38 patients (9 patients with diabetes and 29 control subjects without defects in the entoptic field) said they saw something when angiograms or photographs or both showed nothing (false-positive). Thus, the sensitivity and specificity (using angiograms or photographs or both as the gold standard) with which untrained patients with diabetes detect their own parafoveal area defects are 51% and 82%, respectively. Superimposition of the entoptic image (as drawn by the patient) and the angiograms or color photography or both often showed excellent correspondence. Most (22 of 29) of the control subjects and more than half (40 of 70) the patients with diabetes were able to quantify the size of their foveal avascular zone (FAZ) from the entoptic view, whereas only 22 of 70 of the capillary loops defining the FAZ were visible in the optimal frame of the capillary phase of the fluorescein angiogram. As reported previously in a smaller sample, large FAZs often were associated with poor visual acuity.
More than half the untrained patients with diabetes were able to visualize their own parafoveal retinopathy entoptically, and most untrained patients with diabetes and control subjects where able to quantify the size of their FAZ. Patients and control subjects without parafoveal defects rarely report defects not visible photographically. Patients can be trained to detect their defects. Clinical entoptic monitoring will require verification that patients can detect changes in their retinopathy. Entoptic testing is low cost, noninvasive, and can be performed as often as needed at no risk to the patient. It is, therefore, a promising research technique for subjective monitoring of the early natural history of parafoveal area disease processes.
使用优化的中央凹旁视网膜血管系统内视观察的研究表明，正常受试者在中央凹比在荧光素血管造影中通常所见能更详细地看到自己的毛细血管。作者将这些研究扩展到糖尿病患者，以评估他们在未经训练的情况下检测和定位自己中央凹旁视网膜缺陷的敏感性、特异性和准确性。
使用麦克斯韦观察光学系统的血管内视镜可创建中央凹旁区域视网膜血管异常的高对比度内视图像。采用双盲方案，70例糖尿病患者和29例对照受试者描述、绘制并量化了他们的内视图像。将这些内视记录与内视评估后立即获得的血管造影照片和彩色照片进行比较。
血管造影照片或彩色照片或两者均显示，70例糖尿病患者中有61例在血管内视镜视野（根据所使用的血管内视镜，为8.1度或11.6度圆形视野：中央凹旁区域约为9.7度）内存在视网膜缺陷（如微动脉瘤或渗出物或两者皆有）。在这61例糖尿病患者中，51%（31例）在内视视野中观察到与血管造影照片或两者中的视网膜缺陷相对应的暗“点”或“斑”。38例患者（9例糖尿病患者和29例内视视野无缺陷的对照受试者）中有7例（18%）表示在血管造影照片或两者均未显示任何异常时他们看到了东西（假阳性）。因此，未经训练的糖尿病患者检测自己中央凹旁区域缺陷的敏感性和特异性（以血管造影照片或两者作为金标准）分别为51%和82%。患者绘制的内视图像与血管造影照片或彩色照片或两者的叠加通常显示出极好的对应性。大多数（29例中的22例）对照受试者和超过一半（70例中的40例）糖尿病患者能够从内视图像中量化他们的中央凹无血管区（FAZ）的大小，而在荧光素血管造影的毛细血管期最佳帧中仅能看到定义FAZ的70个毛细血管环中的22个。如先前在较小样本中所报道的，大的FAZ通常与视力差相关。
超过一半未经训练的糖尿病患者能够通过内视观察到自己的中央凹旁视网膜病变，并且大多数未经训练的糖尿病患者和对照受试者能够量化他们FAZ的大小。没有中央凹旁缺陷的患者和对照受试者很少报告照片中不可见的缺陷。患者可以接受训练以检测他们的缺陷。临床内视监测将需要验证患者能够检测到他们视网膜病变的变化。内视检测成本低、无创，并且可以根据需要随时进行，对患者无风险。因此，它是一种用于主观监测中央凹旁区域疾病早期自然史的有前景的研究技术。
