5 U.S.C. § 8105: Total disability

(a) If the disability is total, the United States shall pay the employee during the disability monthly monetary compensation equal to 66⅔ percent of his monthly pay, which is known as his basic compensation for total disability. (b) The loss of use of both hands, both arms, both feet, or both legs, or the loss of sight of both eyes, is prima facie permanent total disability.