adjuster (a juster)

A person who adjusts; An in that which regulates. adjusting-cone (a-jus'ting-kōn), n. strument for measuring the distance between the axes of the eyes when they are parallel, as in looking at a distant object. It consists of two hollow cones, each perforated at the apex. Through these perforations the person whose eyes are to be measured looks at a distant object, and the cones are moved until the two fields of vision coincide. The distance between the apexes then gives the measurement sought.