what is cylinder and axis
A right circular cylinder with radius r and height h. A cylinder (from Greek ÎºÏÎ»Î¹Î½Î´ÏÎ¿Ï â kulindros, roller, tumbler) is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given straight line, the axis of the cylinder.
Cylinder power always follows sphere power in an eyeglass prescription. Axis. This describes the lens meridian that contains no cylinder power to correct astigmatism. The axis is defined with a number from 1 to 180. The number 90 corresponds to the vertical meridian of the eye, and the number 180 corresponds to the horizontal meridian.