The Most convenient form of a cross cylinder is a combination of –
The most convenient form is a combination of a -0.5D sphere with a + 1.0D cylinder which has an effective strength of + 0.5D cylinder in one meridian and -0.5D in other.
–0.5 Diopter sphere with +1 Diopter Cylinder
+0.5 Diopter sphere with –1 Diopter Cylinder
+0.25 Diopter sphere with –0.5 Diopter Cylinder
–0.25 Diopter sphere with +0.5 Diopter Cylinder