From the San Giovanni di Dio hospital, Clinica Oculistica, Azienda Ospedaliera Universitaria di Cagliari, Cagliari, Italy.
From the Department of Surgical Sciences, Eye Clinic, University of Cagliari, Cagliari, Italy.
Sci Rep. 2019 Feb 5;9(1):1413. doi: 10.1038/s41598-018-38260-5.
The aim of the study was to define and characterize the optical behavior of the tear film during visual fixation in humans on en-face optical coherence tomography (OCT). We included 20 healthy participants, 60% female, aged from 25 to 42 years (33.05 ± 4.97 [mean ± SD]) and ten patients with severe dry eye, 50% female, aged from 26 to 42 years (33.7 ± 5.31). To perform high-resolution tear film imaging, participants were asked to gaze at the internal fixation point in the spectral-domain anterior segment OCT device, and meanwhile scanning session was executed at the following time-points after blinking: at the 2, 3, 4, 5, and 6 second. After one hour, OCT imaging was repeated (second session) by a different operator masked to the study to verify the reliability of results. During each measuring session, a pulse oximetry was used for continuously measuring the heart rate and oxygen saturation (SpO%). A preliminary experiment was also performed to test the absence of geometric patterns from the anterior surface of a motionless artificial eye. OCT imaging showed a motionless, stable anterior surface of the artificial eye and in dry eye patients. Conversely, in the healthy participants of the study, a bull's eye pattern of the tear film was detected by OCT at the 2, 3, 4, 5, and 6 second after blinking, respectively, in 45%, 60%, 45%, 60%, and 40% of OCT scans during the first session, and in 35%, 65%, 65%, 60%, and 35% of cases in the second session. Overall, a total of 200 OCT scans were performed in normal human population. A significant correlation was found between the novel tear film pattern and heart rate during the first and the second session (p < 0.01) in healthy eyes. Conversely, no correlation was revealed with SpO2%. Intraclass correlation (ICC) analysis for OCT imaging of the tear film revealed a statistically significant reproducibility of the results (ICC = 0.838; p < 0.01), indicating the high level of reliability of the method, independently of heart rate and SpO2% variables. There exists a novel, geometric pattern of the tear film during visual fixation detectable by en-face OCT, which is mainly evident as heart rate increases. Its discovery implies in turn the presence of a specific vibration (or imperceptible motion) of the tear film that, at present, is not recognized and corrected by the OCT software (in image postprocessing) unlike other eyeball movements.
本研究旨在定义和描述人类在正视光学相干断层扫描（OCT）下注视时泪膜的光学行为。我们纳入了 20 名健康参与者，其中 60%为女性，年龄 25 至 42 岁（33.05±4.97[均值±标准差]），10 名严重干眼症患者，其中 50%为女性，年龄 26 至 42 岁（33.7±5.31）。为了进行高分辨率的泪膜成像，参与者被要求注视频谱域眼前节 OCT 设备中的内部固视点，同时在眨眼后 2、3、4、5 和 6 秒执行扫描。1 小时后，由对研究结果设盲的另一位操作人员重复 OCT 成像（第二阶段），以验证结果的可靠性。在每个测量阶段，使用脉搏血氧仪连续测量心率和氧饱和度（SpO2）。还进行了一项初步实验，以测试静止人工眼前表面是否存在几何图案。OCT 成像显示人工眼的前表面静止且稳定，在干眼症患者中也是如此。相反，在研究中的健康参与者中，在眨眼后 2、3、4、5 和 6 秒，OCT 分别在 45%、60%、45%、60%和 40%的 OCT 扫描中检测到泪膜的牛眼模式，而在第一阶段的 35%、65%、65%、60%和 35%的 OCT 扫描中，在第二阶段的 200 次 OCT 扫描中总共进行了 200 次 OCT 扫描。在健康眼中，第一和第二阶段（p<0.01）中发现新的泪膜模式与心率之间存在显著相关性。相反，与 SpO2%无相关性。OCT 泪膜成像的组内相关（ICC）分析显示结果具有统计学上的重现性（ICC=0.838；p<0.01），表明该方法的可靠性高，独立于心率和 SpO2%变量。在正视 OCT 下，可检测到泪膜存在一种新的几何图案，主要表现为心率增加。其发现反过来意味着泪膜存在特定的振动（或不可察觉的运动），而目前，与其他眼球运动不同，OCT 软件（在图像后处理中）没有识别和纠正这种振动。
