The LEA SYMBOLS^® 2.5% Single Symbol Book Set is a low contrast tool to measure visual acuity in low-light environments. The testing procedure is identical to measuring visual acuity at high contrast. The 2.5% test is the most practical low contrast test for clinical use. Single optotype line sizes from 20/200 to 20/8 (6/60 to 6/2.4) equivalent. This book also provides decimal and logMAR scales for each line size. Includes isolating mask, response key, instructions, and 13 offset pages for easy flipping.

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

Test distance: 10 feet/3 meters.