How to Read Your Prescription (RX)?

When you get your eye prescription from your doctor, you may be confused by the tables, abbreviations, and numbers on it. What do they all say on the prescription? How to read your prescription is also very important for buying prescription eyeglasses online, that’s why we had to understand the meaning of the above items.

What do all these letter abbreviations and numbers mean?

The letter abbreviations on your glasses prescription represent the headings of the various parameters of the eye, while the numbers accurately describe your visual needs. Normally, you will see a few abbreviations and numbers to mark all the important data on your prescription. The following content will explain the meaning of each content in detail for you.

OD, OS Eye

You will often see them on the far left side of the prescription form.

‘OD’ means left eye, which is short for Latin oculus sinister.

‘OS’ stands for your right eye, which is short for the Latin oculus dexter.

Occasionally, you can see ‘OU’, which represents Latin oculus uterque, which refers to both eyes.

SPH, CYL, AXIS and PD

Normally, you can see them on the top of your prescription form.

‘SPH’ (sphere or spherical) means the degree of nearsightedness or farsightedness, and it indicates the value of lens power you need to see clearly.

‘CYL’ (cylinder or cylindrical) measures the degree of astigmatism, if you do not have astigmatism, the corresponding table is blank instead of a number.

‘Axis’ refers to the orientation of astigmatism, it is the number between 1 to 180. So, with astigmatism, you must have an Axis number and vice versa.

‘PD’ (pupillary distance) represents the distance between your eyes. This number is important for the production of prescription eyeglasses. If this number is not listed on your prescription, please see How to measure your own PD. We explain in detail how to measure the pupillary distance yourself or with the help of family and friends.

ADD and Prism

‘ADD’ (addition) indicates the additional lens power for reading to multifocal (progressive or bifocal) lenses. Typically, it will be a positive number (+) and the same for both eyes. Only one number may be written in the table, but it represents the same additional degree for both eyes.

‘Prism’ is used to correct eye alignment issues, which include a prism and base value. It is prescribed to compensate for eye alignment problems. Check prism glasses for more details

Generally, your prescription will be in the form of one of the middle of the following

- Nearsighted Prescription

A prescription with a "-" sign in front of the number under the SPH column represents a nearsighted prescription and is primarily used to correct situations where you can't see distant objects.

- Farsighted Prescription

A prescription with a "+" sign in front of the number under the SPH column represents a farsighted prescription and is primarily used to correct situations where you can't see near clearly.

- Astigmatism Prescription

If there are numbers in the CYL and Axis columns on your prescription, that means you have astigmatism and the direction of that astigmatism. Astigmatism is independent and has nothing to do with your SPH degree.

- Progressive and Bifocal Prescription

A prescription with numbers under the ADD or NV column stands for progressive and Bifocal prescription. This kind of multifocal prescription is used to correct both nearsightedness and farsightedness on one lens with (bifocal) or without a line (progressive).