is a chart used to
subjectively measure visual acuity. Eye charts are often used by health care
professionals, such as optometrists, physicians or nurses, to screen persons
for vision impairment. Ophthalmologists, physicians who specialize in the eye,
also use eye charts to monitor the visual acuity of their patients in response
to various therapies such as medications or surgery.
Benefits & Features
The eye chart is made of letters used as
"optotypes," or symbols designed for vision testing. This standard
chart consists of 11 lines of block letters, beginning with a large single
letter on the top row. The number of letters on each row increases moving from
top to bottom. The size of the letters progressively decreases, allowing for
more letters on each subsequent line.
The Snellen eye chart is read by covering one
eye and reading aloud the letters on the chart, beginning at the top and moving
toward the bottom. The smallest row of letters that the patient reads
accurately determines visual acuity in the uncovered eye. The other eye also is
tested, and both eyes are tested together.1The results are based on what you can see from 20 feet away
compared to what someone with normal eyesight would see. It's why normal human
eyesight is sometimes expressed as 20/20.Your results are determined by the
smallest line of letters you can accurately read on the chart.