Free app is available on Facebook , Android , iOS and on desktop browsers . It starts with up to 81 squares and asks you to identify the different shade . Board grows to four squares and differentiation is subtle each time . And a score of 31 or above is a considered a sign of 'great eyesight '
Free app is available on Facebook , Android , iOS and on desktop browsers . It starts with four squares and asks you to identify the different shade . Board grows to up to 81 squares and differentiation is subtle each time . And a score of 31 or above is a considered a sign of 'great eyesight '