Akil Handan, Dastiridou Anna, Marion Kenneth, Francis Brian A, Chopra Vikas
Doheny Image Reading Center, Doheny Eye Institute, 1355 San Pablo Street, Los Angeles, CA, 90033, USA.
Department of Ophthalmology, David Geffen School of Medicine, Los Angeles, CA, USA.
BMC Ophthalmol. 2017 Mar 23;17(1):31. doi: 10.1186/s12886-017-0425-3.
First reported study to assess the effect of diurnal variation on anterior chamber angle measurements, as well as, to re-test the effects of lighting and angle-of-incidence variation on anterior chamber angle (ACA) measurements acquired by time-domain anterior segment optical coherence tomography (AS-OCT).
A total of 30 eyes from 15 healthy, normal subjects underwent anterior chamber imaging using a Visante time-domain AS-OCT according to an IRB-approved protocol. For each eye, the inferior angle was imaged twice in the morning (8 am - 10 am) and then again in the afternoon (3 pm - 5 pm), under light meter-controlled conditions with ambient room lighting 'ON' and lights 'OFF', and at 5° angle of incidence increments. The ACA metrics measured for each eye were: angle opening distance (AOD, measured 500 and 750 μm anterior from scleral spur), the trabecular-iris-space area (TISA, measured 500 and 750 μm anterior from scleral spur), and scleral spur angle. Measurements were performed by masked, certified Reading Center graders using the Visante's Internal Measurement Tool. Differences in measurements between morning and afternoon, lighting variations, and angle of incidence were compared.
Mean age of the participants was 31.2 years (range 23-58). Anterior chamber angle metrics did not differ significantly from morning to afternoon imaging, or when the angle of incidence was offset by 5° in either direction away from the inferior angle 6 o'clock position. (p-value 0.13-0.93). Angle metrics at the inferior corneal limbus, 6 o'clock position (IC270), with room lighting 'OFF', showed a significant decrease (p < 0.05) compared to room lighting 'ON'.
There does not appear to be significant diurnal variation in AS-OCT parameters in normal individuals, but lighting conditions need to be strictly controlled since variation in lighting led to significant variability in AS-OCT parameters. No changes in ACA parameters were noted by varying the angle-of-incidence, which gives confidence in being able to perform longitudinal studies in approximately the same area (plus/minus 5° of original scan location).
首次报道的研究旨在评估昼夜变化对前房角测量的影响，以及重新测试照明和入射角变化对通过时域眼前节光学相干断层扫描（AS-OCT）获得的前房角（ACA）测量的影响。
根据机构审查委员会（IRB）批准的方案，使用Visante时域AS-OCT对15名健康正常受试者的30只眼睛进行前房成像。对于每只眼睛，在早晨（上午8点至10点）对下角成像两次，然后在下午（下午3点至5点）再次成像，在光度计控制的条件下，室内环境照明“开”和灯“关”，并以5°入射角增量进行。为每只眼睛测量的ACA指标包括：房角开放距离（AOD，从巩膜突向前500和750μm处测量）、小梁-虹膜间隙面积（TISA，从巩膜突向前500和750μm处测量）和巩膜突角度。测量由经过认证的、蒙眼的阅读中心评分员使用Visante的内部测量工具进行。比较了早晨和下午测量值、照明变化和入射角之间的差异。
参与者的平均年龄为31.2岁（范围23 - 58岁）。前房角指标在早晨到下午成像时，或当入射角从下角6点位置向任一方向偏移5°时，均无显著差异。（p值0.13 - 0.93）。在角膜缘下角6点位置（IC270），室内照明“关”时的角度指标与室内照明“开”时相比，显著降低（p < 0.05）。
正常个体中，AS-OCT参数似乎没有显著的昼夜变化，但由于照明变化会导致AS-OCT参数出现显著差异，因此需要严格控制照明条件。改变入射角时，ACA参数未出现变化，这使得有信心能够在大致相同的区域（原始扫描位置的正负5°）进行纵向研究。
