Source:http://linkedlifedata.com/resource/umls/id/C0184189
UMD: Vision assistive devices designed to facilitate reading by highlighting the lines of print being read. These devices usually consist of a black plastic or cardboard piece with one or more slots that is placed over the text, permitting easier reading by showing only one or a few lines of print. Typoscopes eliminate glare from the printed paper; they are intended mainly for use as low-vision aids.