A test for simultaneous binocular vision and for detecting ocular suppression. It consists of five equally spaced opaque, parallel bars crossed by two perpendicular bars. It is held between the reader's eyes and a page of print. The bars being perpendicular to the lines of the text occlude some letters (along vertical strips) to one eye, but these letters are seen by the other eye. If binocular vision is present no difficulty is experienced in reading the page. This instrument represents the most common type of bar reader.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann