The optotypes of ETDRS chart were made from Sloan's letters, which are a set of 10 sans-serif capital English characters (C, D, H, K, N, O, R, S, V, Z) with specified angles and curvatures for each. Therefore, character charts are being taken more seriously and have become the dominant way to evaluate VA clinically around the world, such as the well-known ETDRS chart. To approximate a person's visual tasks, the optotypes (visual targets) of a functional VA chart should be related to person's mother language and cultural background. These charts are useful and have claimed to be unaffected for testing subjects with various cultural background.Īccurate measurement of the functional vision for daily activity is essential as it is often required for certain job qualifications, disability benefits, and low vision rehabilitation. The break or the spacing is designed with one-fifth the optotype height which subtends 1 minarc, the resolution limit of human eyes. Universal standard VA charts like Landolt C and Snellen E utilize the break of the ring and the spacing of the adjacent strokes, respectively, to determine the VA. This is usually measured using VA charts with various angular size of detail (MAR, minimum angle of resolution). VA is a measure of the ability to determine details. We also investigated the legibility of TC characters in BK and ML fonts in normal-sighted subjects to find the relationship between the functional vision of TC language and the angular size of Early Treatment Diabetic Retinopathy Study (ETDRS) chart.

In this study, we measured the actual printed font size of TC characters in near charts to decrease the bias caused by em square. However, different publishers utilize various spacing between the printed TC character and the surrounding space around each character resulting in a nonuniform actual font size of TC characters. In Taiwan, taking into consideration, the legibility and readability of literatures for low vision populations and the elderly, government entities recommend publishers to use larger font sizes in their printed matter. However, there is no standardization of the spatial occupation of TC characters in an em square presently. In fact, there are a wide variety of Traditional Chinese (TC) font types commercially available.

National examinations and school textbooks in Taiwan use BiauKai (BK, 標楷體) and MingLiU (ML, 新細明體) as standard font types.

Font style for traditional chinese