If you have recently been to the eye doctor and find yourself with a prescription you'd like to know a little more about, you've come to the right place. There are countless abbreviations, symbols, and numbers on different prescriptions, and it is important to determine what they mean to be a well-informed consumer and patient. If your doctor doesn't volunteer this information, make sure to ask, check online, or read the following information.
Your Diagnosis
Your ophthalmologist will have likely diagnosed you with nearsightedness, farsightedness, or astigmatism, and the next step is purchasing a pair of designer lenses or prescription glasses. With paper in hand, you walk into your closest eyeglass store, only to wonder what you're actually looking for.
OD vs. OS
OD and OS are abbreviations for oculus dexter and oculus sinister respectively. These are both Latin terms for right eye and left eye, and will simply help the optometrist find the best prescription lens for each eye. Some modern doctors may go a less-traditional route and simply abbreviate using RE and LE.
Sphere
Sphere can also be abbreviated on prescriptions using SPH, and the number indicates the lens power for the prescription lenses you need. The value is measured in diopters (D) and can be either positive or negative. A positive sphere value means that you are farsighted, while alternatively, a negative sphere value indicates that you are nearsighted. On most people, this number will differ between each eye.
Add
Another column or row that may be on your prescription is entitled Add. This indicates the magnifying power that will be added to the bottom part of your lens. This will only apply if you decided to purchase a prescription multifocal lens.
Cylinder
If you suffer astigmatism, a defect arising from the spherical curvature of your eye, your prescription will probably have a value under CYL. This indicates your specific lens power, which unlike the power in near and farsighted individuals involves meridians and a complex combination of curvatures and specific variations in lens power.
Keep in mind that the above information pertains to eyeglass prescriptions, as contact lenses are unfortunately a whole other story. Contact lenses will also require information about the base curve and lens diameter.
Although there may be other abbreviations or unknown terms on your prescription, the four described above are the most common. When in doubt, make sure to ask your eye doctor or optometrist for specific information to help you understand your prescription lens.
