When there is the character of "Cylinder" on the contat lenses' packings, that means the astigmatism presceiption. Unlike the short sighted eyes, the astigmatism eyes is a kind of refractive error status, with the cornea and lens surface bending not agree about. Sometimes the cylinder is abbreviated with "C" or "Cly". If you have the astigmatism, the eyeglasses or contact lenses must add such lenses with "C" to help you see clearly.
Hi, I searched and found that "Cylinder" is a measurement of astigmatism. To my surprise, astigmatism is said to be caused by the eye's cornea (corneal astigmatism) or lens (lenticular astigmatism) being oval rather than round. The cylinder number shows just how oval the eye is. If the cylinder number is positive, it means the person is far sighted. A minus sign means they're near sighted. Well, i think things about this cylinder is quite clear now, Hoe my answer can be useful to you.
The cylinder is the astigmatism which relates to the shape of your eye. It means you can see shape better, thus you can distinguish two similar objects. For instance, you would see the letter l as l rather than the letter i. the axis is part of the cylinder. The lens should be at a certain orientation (axis) for the cylinder to work.