The Crowded Symbol Book is designed for testing children and adults who
have difficulty in reading the optotypes on the big charts. This test is
the smallest line test when the central symbol is used as the test
symbol. The four symbols surrounding the central symbol interfere with
the recognition of the central symbol closely the same way they do in
line acuity charts. Because of the crowding effect, it often allows
measurement of line acuity of young children much earlier than the
visual acuity charts and thus helps in detecting amblyopia or impaired
vision early. Line sizes from 20/63 to 20/16 (6/19 to 6/4.8) equivalent,
0.63 to 1.25. Includes response key, training cards, and instructions.
16 offset pages, 5" x 5" (12.7 cm x 12.7 cm).