Understanding Your Prescription
Trying to decipher your prescription is a common issue for many people. All those letters and numbers can be confusing, but breaking up the abbreviations and measurements into individual pieces can make them easier to understand. Before we get to the decoding process, here are three of the most common eye conditions that require a prescription in the first place:
- Myopia—commonly called nearsightedness, which makes distance vision blurry
- Presbyopia—commonly called farsightedness, which makes near vision blurry
- Astigmatism—which focuses light on more than one spot on the retina, making vision blurry
These are all refractive errors that simply mean your eyes have trouble focusing light correctly. The prescription you will receive for these conditions is measured in units called diopters. Diopters represent the amount of correction you need to normalize your vision. The more nearsighted (or farsighted) you are, the higher your prescription in diopters.
On your prescription, you’ll see some letters followed by a series of numbers. The letters “OD” indicate that the prescription is for your right eye; “OS” represents your left eye. Your prescription, including both eyes, will generally look something like this:
OD -4.00 -1.50 x 180
- Refractive Power – The first number in the series identifies your degree of nearsightedness or farsightedness. A plus sign (+) indicates you are farsighted, a minus sign (-) indicates you are nearsighted. This number is called your spherical correction.
- Astigmatism –The second number in your prescription identifies what degree of astigmatism you have i.e. how well or poorly your eye focuses light onto the retina. The number can be written either with a (+ sign) or a (- sign). This number is called your cylindrical correction.
- Axis – The third number indicates the direction of your astigmatism. For example, an axis of 180 degrees means the astigmatism is horizontal. If your prescription doesn’t have a second or third number, you most likely don’t have astigmatism.
- DV vs. NV – Your prescription might also contain the abbreviations DV (distance vision) or NV (near vision). DV is the portion of your prescription which corrects your ability to see things far away. NV means your prescription is for reading only.
You may be surprised to learn that your left and right eyes can have different prescriptions, but this isn’t uncommon. If your eyes are different, your VSP doctor can provide a different prescription for each eye to meet your specific needs.
If you think you're due for a prescription update, make an appointment with your eye doctor for an eye exam.