obliquely crossed cylinder
crossed cylinder, obliquely
Two cylindrical lenses combined together with their axes neither parallel nor perpendicular. The combination can be replaced by a single sphero-cylindrical lens in which the two focal lines are perpendicular to each other. The powers and axis of this new lens can be determined graphically or mathematically. An analogous situation obtains when the cylindrical correction of an eye is corrected by a cylindrical lens placed at an incorrect axis before the eye.