Eye Exam Chart

There are many eye exam charts found in the hospitals of UK and in EENT clinics. UK professionals in the medical field call this the Snellen chart. It is an eye chart used by eye care professionals and others to measure visual acuity. The Snellen Chart was developed by the Dutch ophthalmologist Herman Snellen in 1862.

The original Snellen chart is printed with eleven lines of block letters. The first line consists of one very large letter, which may be one of several letters, for example E, A, H, or N. The rows that follow below each series of letters have increasing numbers of letters that decrease in font size. If you take the test, you will be required to cover one eye, and read aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates your visual acuity in that eye. Then you do the similar process, this time covering the other eye.

The symbols on an acuity chart are formally known as "optotypes." In the case of the traditional Snellen chart, the optotypes have the appearance of block letters, and are intended to be seen and read as letters. The letters from the Snellen chart, however, are not letters found from any ordinary typographer's font.