How to interpret an eye prescription

Correct reading of the eye prescription

You will have had an eye check and in order to order your new glasses you will be given a prescription. Clearly professionals will take care of the accuracy of the reading diagnosis but if you want to understand the differences from previous prescriptions, we will reveal how to read an eye prescription before going to a trusted store and buying a frame. This step can also be useful if you want to buy glasses online: you will be able to fill in the fields independently, saving time and probably also money on the total bill.

An eye prescription is key for understanding a person’s vision needs and getting the correct glasses or contact lenses; it is unique for each individual and is drawn up by a qualified ophthalmologist or optician. It contains a series of values and abbreviations that indicate the optical correction necessary to correct any visual defects. Let’s see together how to interpret it.

Interpupillary distance

The interpupillary distance is the measure in millimeters of the distance between the pupils; this information is essential to correctly center the eyeglass lenses in relation to the eyes. It can be reported as a single value or as two separate values for the right eye and the left eye.


The sphere indicates the necessary correction for myopia (negative values) or farsightedness (positive values). A negative value indicates the amount of correction for nearsightedness, while a positive value indicates the amount of correction for farsightedness; it can be followed by a “+” or “-” sign depending on the visual defect.

Cylinder and Axis

The cylinder and axis are values associated with astigmatism. The former indicates the amount of correction needed for the astigmatism, while the latter represents the direction of the astigmatism measured in degrees. This information is often referred to together and is preceded by a “+” or “-” sign.


Addition is a measure of the additional correction needed for presbyopia, a condition that occurs with aging and makes it difficult to focus on close-up objects; this value is especially important for people who need multifocal glasses or progressive lenses.


The prism is an additional indication that can be present in an eye prescription; indicates the presence of a deviation of the eye, known as strabismus and can be indicated with a numerical value representing the extent of the deviation and a direction in degrees.

Values for right eye and left eye

An eye prescription may contain separate information for the right eye and the left eye which may vary for these two eyes and must be interpreted separately. It is important to underline that the reading and interpretation of an eye prescription should always be entrusted to a qualified professional; an ophthalmologist or optician will be able to explain in detail the specific values of your prescription and advise you on choosing the most suitable corrective lenses for your needs.

Even if you shop online, don’t worry, the best opticians provide a space in which to attach your recipe or prescription, or a contact is indicated via email to forward the prescription to in order to obtain a personalized resolution.