A Snellen chart is an eye chart

Eye chart

An eye chart is a chart used to measure visual acuity. Types of eye charts include the logMAR chart, Snellen chart, Landolt C, and the Lea test.-Procedure:Charts usually display several rows of optotypes , each row in a different size...

 used by eye care professional

Eye care professional

An eye care professional is an individual who provides a service related to the eyes or vision. It is a general term that can refer to any healthcare worker involved in eye care, from one with a small amount of post-secondary training to practitioners with a doctoral level of education.-Current...

s and others to measure visual acuity

Visual acuity

Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....

. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart during 1862. Vision scientists now use a variation of this chart, designed by Ian Bailey and Jan Lovie (see "visual acuity

Visual acuity

Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....

").
The traditional 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, H, or N.