Decoding Your Eyeglass Prescription
If your doctor, like most, is notorious for horribly scribbled handwriting, more often than not you can still decipher what medication he or she has prescribed for you. But have you ever tried reading an eyeglass prescription from your Optometrist or Ophthalmologist? Not so easy.
When I took a look at my most recent eyeglass prescription, it looked like a bunch of random letters and numbers strewn across a page, with a litany of symbols added on top… I was more confused after reading it, then I was beforehand.
Thankfully the team over at All About Vision put together a great article to help dissect your eyeglasses prescription. They go over everything, from the terms and abbreviations used on the prescription, as well as cover the differences between an eyeglass and contact lens prescription.
Here’s a quick reference guide for your next exam…
OD and OS:
The fist thing you will most likely notice on your prescription are the letters “OD” and “OS”. These are actually Latin abbreviations for the terms “Oculus Dextrus”, and “Oculus Sinister”, meaning right eye, and left eye respectively. If you don’t see “OD/OS” your prescription will most likely include the letters “OU,” which is another Latin abbreviation for the term “Oculus Unitas”, meaning both eyes. While the Latin abbreviations are tradition for eyeglass prescriptions, some doctors have started modernizing their prescriptions by using the abbreviations “RE”, or Right Eye, and “LE” (for left eye).
This number tells you the amount of lens power needed to correct your vision. The farther away the number is from zero, the more vision correction you need. If you find a “+” or “-” in front of the number, it means you are farsighted (+) or nearsighted (-) depending on the symbol found.
The Cylinder rating is another important part of your eyeglass prescription, which refers to the amount of Astigmatism in your eyes. The Cylinder number is usually accompanied by a minus sign which represents the difference in power that exists, as the Doctor measures how your eyes focus light. If this column is blank, this would tell you that you either have no Astigmatism, or it is so minimal that correction is not required.
The Axis number describes the position of the Astigmatism in your eye. This number shows the direction the eye doctor needs to position any cylindrical power in your lenses (required for Astigmatism only). Axis numbers are measured in angle degrees ranging from 1 to 180. If the Cylinder section on your prescription is blank, then you will not have an Axis number as the prescription is spherical. The idea is to neutralize the difference in power in the eye with the power in the lens.
Only a small amount of eyeglass prescriptions include Prism. Prism refers to the amount of Prismatic Power needed for your eyes. This is typically prescribed to help correct eye alignment problems, and it not typical for most people.
For those of us who need multi-focal lenses, Add describes the additional magnifying power required to correct Presbyopia. The Add number will usually be the same for both eyes, and is always represented as a positive number, even if it is not preceded by a plus sign on your prescription.
Is it time for your yearly eye exam? Now that you know what you are reading, head on over to your local Cohen’s Fashion Optical and speak with their knowledgeable, and experienced staff to learn more.