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How to read your eye prescription? sph, cyl, axis included

Dec 23,2022

A sure sign that you need glasses is that you have frequent headaches. Your doctor may recommend that you have your eyes checked. The other main reasons for having an eye exam are when you start to have blurred vision and have to keep some distance from the reading material. Blurred vision is called a refractive error and requires glasses. Your vision test will reveal whether you have one of the following refractive errors: nearsightedness, astigmatism, presbyopia, or farsightedness.


One of the absolute musts for glasses is your eye prescription. If you don't have an eye exam, you won't be able to get a pair of glasses. In recent years, many optometrists have performed eye exams individually or given you a package that includes an eye exam. You can choose glasses from different stores depending on your eye prescription, but do you know how to read your eye prescription? It is important for you to know how to read your eye prescription. 

What to include in your eye prescription?

1. OS means oculus sinister, or your left eye

2. OD means oculus dexter, or your right eye

3. SPH means sphere, or the power of the lens that will correct your eyesight

4. CYL means cylinder, or the amount of astigmatism in your eye.

5. Axis is a number between 1 and 180. It indicates exactly where the astigmatism appears on your eye. The cylinder and axis together help correct astigmatism.

6. ADD stands for the additional lens power needed to make it easier for you to read. This number is seen on prescriptions for reading glasses or the lower portion of bifocal or progressive lenses.

7. Prism is used if you have double vision. It indicates the amount of prismatic power your glasses need to correct for differences in the alignment of your eyes.

8. Your prescription may have a ‘base’ column, or it may be included in the same column as ‘prism’ this gives further information about the required prism correction, telling us the orientation needed in the lens.


How to read an eye prescription?

You will find that getting a separate eye prescription will give you more options when choosing eyeglasses. So, you should know how to read eye prescriptions.


By knowing the parameters in some of the recipes above, you can read your prescription. Both eyes are tested separately, which will be recorded as OD or OS (right eye or left eye). Each of these is assigned a number for distance and ADD. Of specific importance is the number under SPH. Additional numbers are allocated under CYL, axis, prism, and base.


You can determine the weakness of your eyes by how far away from zero the number is on your prescription. The farther away, your eyesight will need more correction, which means a stronger prescription. If you are farsighted, the allocated number will have a plus sign. If you are nearsighted, the allocated number will have a minus sign. Included will also be the distance between the centers of the pupils, which is the pupillary distance (PD). Here are an example of what prescription for eyes could look like:


How often should you get an eye exam?

The American Optometric Association recommends eye exams at least every 2 years if you're under 60, and at least once a year if you're over 60.

It's important to check your vision and eye health regularly because some serious eye diseases, such as glaucoma, have no obvious early symptoms. An ophthalmologist can examine your eyes and detect changes early, which can prevent vision loss.


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