RAF Convergence RuleRAF Rule(Royal Air Force Rule) provides a binocular gauge to measure Objective and Subjective Convergence as well as Accommodation in 1 mm increments. The RAF Rule consists of a 50 cm long rule with a slider holding a rotating four sided cube. Each side has a different target. The first has a vertical line with a central dot for convergence fixation. The others provide a limited number of lines of near reading examples. A rest is provided for the