Assessment of Distance Visual Acuity

Myopia can be diagnosed (in combination with other tests) by a distance visual acuity (DVA) test. In the medical office, the Snellen eye chart is most often used. Two types of charts are commonly used in the medical office. One type is used for school-age children and adults and consists of a chart of letters in decreasing sizes. The other type is used for preschool children, non-English- speaking people, and nonreaders; it is composed of the capital letter E in decreasing sizes and arranged in different directions. Visual acuity charts with pictures of common objects are also available for use with preschool­ers. Testing with these charts tends to be less accurate than with the Snellen charts. Some children are unable to iden­tify the objects because of lack of recognition, not because of a defect in visual acuity. It is suggested that the Snellen Big E chart be used with preschoolers.

Figure. A Snellen eye chart consisting of letters in decreasing sizes, which is used to measure distance visul acuity.