The Astigmatic / Illiterate Letter E Visual Acuity Chart measures 11" wide x 24" long and is designed to be read at a distance of 20 feet. This Astigmatic/E Chart has a rating of direct: 20/200 to 20/10 (lines also noted in meters). The 180 degree astigmatic clock at the top of the chart is useful in screening for astigmatism. This classic letter eye chart is made of extra strong, non-reflecting, matte finish cardboard, with a brass eyelet for wall mounting. Red and green bars not only serve as a patient reference point during acuity testing, but also hint as to a patient's color perception.