Radner Wolfgang, Radner Michael, Daxer Barbara, Ettl Armin
Karl Landsteiner University of Health Sciences, Dr. Karl-Dorrek-Straße 30, 3500, Krems, Austria.
Department of Ophthalmology, University Hospital St. Pölten, Dunant-Platz 1, 3100, St. Pölten, Austria.
Eye Vis (Lond). 2022 Aug 15;9(1):31. doi: 10.1186/s40662-022-00302-5.
To evaluate microscopically whether the print quality and accuracy of sizing of Landolt ring near vision charts are adequate for the calibration of reading charts.
Near vision charts with Landolt rings from Oculus GmbH (C-Test; Wetzlar, Germany), Precision Vision (Woodstock, IL) and the RADNER Charts were examined, as well as custom-made Landolt rings optimized for print quality. Microscopic investigations and measurements were performed by using a Huvitz HSZ 600 stereomicroscope (Nikon NIS Elements software) to evaluate the height of the Landolt rings, the thickness of the lines, and the width of the openings. The deviations from the mathematically correct values, which were calculated as given in the EN/ISO 8596 and by the International Council of Ophthalmology (ICO), were analyzed (calculated for a test distance of 40 cm).
All the near vision charts showed notable deficiencies in print quality and aberrations from the nominal values in the height, thickness of the lines, and width of the openings. The openings were too narrow, whereas the height and thickness of the lines were larger than the nominal values. Even the openings of Landolt rings optimized for print quality were not always within an acceptable 5% tolerance and need further improvement.
This study reports inaccuracies in the heights, thicknesses of the lines, and widths of the openings of Landolt rings in all the near vision charts investigated. The extent of these inaccuracies excludes such near vision charts as reference tests for the calibration of reading charts. The x-height in relation to the visual angle still seems to be the most reliable method for standardizing the print sizes for reading charts.
通过显微镜评估近视力表中兰氏环的印刷质量和尺寸准确性是否足以用于阅读视力表的校准。
对来自德国韦茨拉尔的奥culus公司（C-Test）、美国伊利诺伊州伍德斯托克的Precision Vision公司以及RADNER视力表的带有兰氏环的近视力表进行检查，同时也检查了针对印刷质量进行优化的定制兰氏环。使用Huvitz HSZ 600体视显微镜（尼康NIS Elements软件）进行显微镜检查和测量，以评估兰氏环的高度、线条厚度和开口宽度。分析与数学上正确值的偏差，这些偏差是按照EN/ISO 8596以及国际眼科理事会（ICO）给出的方法计算得出的（针对40厘米的测试距离进行计算）。
所有近视力表在印刷质量方面均存在明显缺陷，并且在高度、线条厚度和开口宽度方面与标称值存在偏差。开口过窄，而线条的高度和厚度大于标称值。即使是针对印刷质量进行优化的兰氏环开口也并非总是在可接受的5%公差范围内，需要进一步改进。
本研究报告了在所研究的所有近视力表中，兰氏环的高度、线条厚度和开口宽度存在不准确之处。这些不准确的程度排除了此类近视力表作为阅读视力表校准参考测试的可能性。与视角相关的x高度似乎仍然是标准化阅读视力表印刷尺寸的最可靠方法。
