After getting a comprehensive eye exam and finding out you need vision correction, you may find yourself confused on what your eyeglass prescription means. Your optometrist should tell you whether you’re nearsighted, farsighted, or if you have an astigmatism. However, beyond your diagnosis, the abbreviated words on your prescription are a mystery to many patients. So, what does it all really mean? Use this simple guide to identify and determine what your doctor wrote down!
OD and OS
The first step in understanding your eyeglass prescription is knowing the difference between OD and OS. OD and OS are actually abbreviated Latin terms, with OD simply meaning the right eye and OS meaning the left. These abbreviations are traditional and used by many doctors, but some have modernized OD and OS to RE (right eye) and LE (left eye). These terms can be found on prescriptions for eyeglasses and contact lenses.
Additional Abbreviations and Terms
There are many other terms beyond just OD and OS. Here are a few other abbreviations you may notice on your prescription.
CYL
CYL is short for ‘cylinder.’ This indicates the power of the lens the doctor prescribed in order to correct astigmatism. However, if there is no number under this column then this means that you do not have an astigmatism or it does not need to be corrected according to your doctor.
SPH
SPH is short for ‘sphere.’ This indicates the power and strength of the lens the doctor prescribed in order to correct your vision. In the case that you are nearsighted, also called myopia, the number will have a minus sign in front of it(-). For farsightedness, also called hyperopia, the number will have a plus sign (+).
Axis
If your doctor included the cylinder power on your prescription, your doctor would have also included the ‘axis value’ which indicates positioning. Axis is measured in degrees from 1 to 180. The measurements are referring to the astigmastism, and it locates it’s positioning on the cornea.
Add
Add is exclusively for multifocal lenses. Add just tells the extra magnifying strength for the bottom section of the lens that was added for those who are nearsighted. The number for this section will always have a plus sign (+). Typically Add is for patients over 40 because natural aging causes the need for additional vision correction.
Notations
You may notice lens recommendations on your eyeglass prescription. This is a specific recommendation from your doctor that are optional but put there for you to consider. There are a few notations you may see.
Anti-reflective Coating
Anti-reflecting coating is also referred to as ‘AR coating.’ This special coating reduces reflection in order to allow more light to pass through the lenses.
Photochromic Lenses
Photochromic lenses are able to darken automatically when exposed to the sunlight. Therefore, being able to change tint in reaction to varying levels of light exposure. Photochromic lenses are also referred to as variable tint lenses or light-adaptive lenses.
Progressive Lenses
Progressive lenses have no ‘line’ through the middle of it, creating a smooth transition between the varying focal lengths. Progressive lenses correct vision at all distances.
Eyeglasses VS Contact Lens Prescription
Your eyeglass prescription includes all the necessary information for you to pick the correct eyeglasses. However, this does not mean that your eyeglass prescription can give you the correct details for your contact lenses. Keep in mind when purchasing contact lenses you need the lens diameter, the curve of the back surface of the contact lens, and the brand name.