Photometric Compliance of Tablet Screens and Retro-Illuminated Acuity Charts As Visual Acuity Measurement Devices.
Photometric Compliance of Tablet Screens and Retro-Illuminated Acuity Charts As Visual Acuity Measurement Devices.
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DOI：
10.1371/journal.pone.0150676
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Hamilton R
中科院分区：
文献类型：
--
作者：
Livingstone IA;Tarbert CM;Giardini ME;Bastawrous A;Middleton D;Hamilton R
移动技术越来越多地用于测量视力。基于图表的灵敏度测试标准规定了亮度、光型对比度和亮度均匀性的光度要求。制造商提供了一些光度数据，但对视力测试的片剂性能知之甚少。本研究对7台平板电脑（iPad, Apple inc.）和3张ETDRS（糖尿病视网膜病变早期治疗研究）视力表进行了光度表征，并将结果与视力测量标准进行了比较。平板电脑屏幕的亮度和对比度是用黑白棋盘测试屏幕上的9个点在5个任意亮度水平下测量的。测量ETDRS光型和相邻白背景亮度和对比度。所有7片（室内灯关闭）均超过了最严格的平均亮度要求（≥120 cd/m2），标称亮度设置高于50%。无论亮度设置如何，均超过对比度要求（Weber≥90%），5个略低于所需亮度均匀性阈值（Lmin/Lmax≥80%）。在室内开着灯的情况下重新评估三片药片，对平均亮度和对比度的影响不大，亮度均匀性也有所改善，甚至超过了阈值。三张EDTRS图（室内关灯）的平均亮度（≥120 cd/m2）和韦伯对比度（≥90%）都足够，但三张图均未达到亮度均匀性标准（Lmin/Lmax≥80%）。两个图表超出了制造商建议的灯具更换时间表。在室内开灯的情况下，图表平均亮度和韦伯对比度均有所增加，但仍有两张图表亮度均匀性不足。平板电脑显示出更少的设备间变化，更高的对比度，以及比图表更好的亮度均匀性，在开灯和关灯的环境中，提供亮度设置为50%。总体而言，iPad平板电脑在高对比度锐度标准的光度依从性方面与ETDRS图表相匹配或略微优于ETDRS图表。
Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for luminance, optotype contrast and luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean luminance or contrast, and improved luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer’s recommended lamp replacement schedule. With room lights on, chart mean luminance and Weber contrast increased, but two charts still had inadequate luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out-performed ETDRS charts in terms of photometric compliance with high contrast acuity standards.