these cards can be used for presentation as single optotype or arranged in a row as a line test - when the cards are next to each other, the space between the numbers is equal to the width of the symbols. To determine the visual acuity use the following formula:
VA=Viewing Distance Used (meters) / M-value
Measurements: 60M cards are 6x9 in (15x23cm) - 40M cards are 4x6 in (10x15cm)