Bhandari Khob R, Ostrin Lisa A
University of Houston College of Optometry, Houston, USA.
Ophthalmic Physiol Opt. 2020 Nov;40(6):801-814. doi: 10.1111/opo.12735. Epub 2020 Oct 1.
To validate the Clouclip, a continuously measuring objective rangefinder, and examine viewing behaviours during various near tasks in non-myopic and myopic adults.
In experiment 1, five Clouclip devices were utilised. An infrared camera was used to visualise and measure infrared beam size and angle. Repeatability for distance tracking was assessed from 5 to 120 cm in 5 cm increments. Accuracy of distance tracking was investigated for paper and iPad targets, spatial integration was calculated, effects of target tilt were determined and light measurements were compared to a lux meter. In experiment 2, viewing behaviour was assessed in 41 subjects (21 non-myopic, 20 myopic) during four 15-min near tasks; (1) passive reading of printed material, (2) active writing on printed material, (3) passive viewing on an electronic device and (4) active engagement on an electronic device. Working distance was compared between tasks and refractive error groups.
Clouclip distance tracking showed good repeatability, with a mean difference of 0.34 cm and limits of agreement of ±2.0 cm. Clouclip-measured and actual distances were highly correlated for paper and electronic targets from 5 to 120 cm, with mean differences and limits of agreement of 3.96 ± 13.78 cm and 4.48 ± 8.92 cm, respectively; variability increased for distances >100 cm. Tracking ability increased with larger target sizes; tracking was accurate when the target occupied 1.5%-20.3% of tracking beam area, depending on distance and with target tilt up to ±60 degrees. Clouclip- and lux meter-measured ambient illumination were highly correlated for a wide range of intensities (r = 0.96, p < 0.001), but with greater variability for intensities >20 000 lux. The Clouclip infrared beam was measured to have a diameter of 25.6 ± 2.2° and a downward angle of 10.3 ± 0.5°. For subject testing, viewing distance was significantly closer for active and passive printed tasks (29.5 ± 6.7 cm and 33.2 ± 8.8 cm, respectively) than for active and passive electronic tasks (35.4 ± 8.0 cm and 40.8 ± 10.4 cm, respectively), with no differences between refractive error groups (p = 0.88).
The Clouclip performed well in measuring near and intermediate distances and could distinguish between indoor (<1000 lux) and outdoor (>1000 lux) illumination. A closer working distance was observed for printed tasks compared to those on an iPad, with no difference in viewing distance between non-myopic and myopic adults.
验证连续测量的客观测距仪Clouclip，并研究非近视和近视成年人在各种近距任务中的观看行为。
在实验1中，使用了5个Clouclip设备。使用红外摄像机来可视化和测量红外光束的大小和角度。以5厘米的增量评估从5到120厘米的距离跟踪重复性。研究了针对纸张和iPad目标的距离跟踪准确性，计算了空间整合，确定了目标倾斜的影响，并将光测量结果与照度计进行了比较。在实验2中，对41名受试者（21名非近视，20名近视）在四项15分钟的近距任务中进行了观看行为评估；（1）被动阅读印刷材料，（2）在印刷材料上进行主动书写，（3）在电子设备上进行被动观看，以及（4）在电子设备上进行主动操作。比较了任务和屈光不正组之间的工作距离。
Clouclip距离跟踪显示出良好的重复性，平均差异为0.34厘米，一致性界限为±2.0厘米。对于5至120厘米的纸张和电子目标，Clouclip测量的距离与实际距离高度相关，平均差异和一致性界限分别为3.96±13.78厘米和4.48±8.92厘米；距离>100厘米时变异性增加。跟踪能力随着目标尺寸的增大而提高；当目标占据跟踪光束面积的1.5%-20.3%时，跟踪是准确的，这取决于距离以及目标倾斜度高达±60度。对于广泛的强度范围，Clouclip和照度计测量的环境照度高度相关（r = 0.96，p < 0.001），但强度>20000勒克斯时变异性更大。测量的Clouclip红外光束直径为25.6±2.2°，向下角度为10.3±0.5°。对于受试者测试，主动和被动印刷任务的观看距离（分别为29.5±6.7厘米和33.2±8.8厘米）明显比主动和被动电子任务的观看距离（分别为35.4±8.0厘米和40.8±10.4厘米）更近，屈光不正组之间没有差异（p = 0.88）。
Clouclip在测量近距和中距方面表现良好，并且可以区分室内（<1000勒克斯）和室外（>1000勒克斯）照明。与在iPad上的任务相比，观察到印刷任务的工作距离更近，非近视和近视成年人的观看距离没有差异。
