The surface powers of a lens can be expressed as a fraction called Toric Notation . This fraction consists of a numerator which describes the front surface of the lens and a denominator describing the back surface. Spherocylinder lenses are made in three forms based on the power in each cardinal meridian and the curvature of each toric meridian and the spherical surface. No power in one meridian 2. Sphere surface plano OR one toric meridian plano 3.
All curves have a finite value.
The cylinder or toric curves can be found on the front or back of the lens. If on the front surface it is referred to as a plus cylinder . If it is on the back it is a minus cylinder . Do the Rotation Test to determine the location of the minus and plus cylinder axes. Since it is a loose lens as opposed to being in a frame, you can hold it any way you want to.