After an eye exam, the doctor will come back in the room and hand you a prescription if there is a need for glasses or contact lenses. When you shop for glasses or contacts, a technician or optician will fill the Optometrist’s written specifications, which is the prescription. There are lots of numbers and abbreviations so it can be quite confusing if you were to just glance over it. However, once the different parts are learned, it can tell quite a bit about focusing power and shape of your eye.
Let’s take a look at my prescription. Notice in the blue circle where it has the abbreviations “OD” and “OS.” That tells you what eye we are talking about. “OD” stands for Oculus Dexter, which is the fancy Latin way of saying “Right Eye” and “OS” stands for Oculus Sinister, which is the not-so-flattering way of saying “Left Eye.”
In the red circle is the the Sphere, Cylinder and Axis. These columns tell you about the focusing ability and shape of the eye. Sphere is commonly referred to as the “power” of the eye. If the number in the “sphere” column is a negative (like my prescription) it means you are nearsighted. Optometrists will call the condition Myopia. If the number is positive (if my prescription were to say +2.75) it means you are farsighted. Like nearsightedness, Optometrists have a special name for farsightedness as well – Hyperopia.
The cylinder and axis will tell if you have an astigmatism or not. That just means your eye is shaped more like a football than it is a basketball. The numbers in the cylinder and axis columns correct for the astigmatism.