The Single Number Book is ideal for situations in which the child/adult cannot perform when tested with a line test. This book can help determine the best resolution of the visual pathway in a child/adult with amblyopia or impaired vision. Single optotype line sizes range from 20/200 to 20/8 (6/60 to 6/2.4) equivalent, 0.10 to 2.50. Includes an isolating mask, instructions, and 13 offset pages for easy flipping.

Dimensions: 5" x 5" (12.7 cm x 12.7 cm).

Testing distance: 10 feet/3 meters.