What makes a prescription? If the eye were a perfect sphere then all we would need to correct vision would be a sphere lens. Though there are many people who can be corrected with a sphere lens many patients require a spherocylindrical lens because they have astigmatism.
A spherocylindrical lens is made up of sphere power and cylinder power.
Optometrists and ophthalmologists think of spherocylindrical lenses differently. Ophthalmologists think of adding the sphere and the cylinder.