When the ophthalmologist or optician graduates our vision and sees that we need optical correction, we usually make a prescription for the glasses or contact lenses that we will have to take to the optician when we go to buy them. But it is not easy to understand what he puts into it. With this small guide you will be able to read and interpret correctly the prescription of your glasses.
The recipe for glasses generally contains apparently cryptic and unintelligible values for those who do not have optical knowledge.
In most cases, the patient does not understand the values, symbols and abbreviations that appear in the graduation prescription of the view given by the professionals. They are faced with unintelligible data with the same meaning for them as a blank paper.
With this brief guide and through practical examples we want to shed some light on this issue and help understand what we have in hand.
The values that are shown in the prescription of your glasses are also those of your visual graduation. That is, the optical correction that your eyes need to have a vision as clear as possible and reach the highest visual acuity (you can know more about the visual acuity in this publication).
Guide to interpret the prescription of the ophthalmologist’s glasses.
Table of Contents
1 Frequent abbreviations at graduation
2 Diopters: the unit of measurement of the refractive error
3 How to interpret the prescription data of glasses
3.1 Sphere (ESF or SPH)
3.2 Cylinder (CIL or CYL)
3.3 Addition (ADD)
3.4 Visual acuity (AV)
4 Complementary values in the graduation recipe
4.1 Prism (PRISM) and base
4.2 Interpupillary distance (DIP)
5 Examples of eyeglass prescriptions
6 Frequently asked questions (FAQ)
6.1 Is the prescription for the glasses also for contact lenses?
6.2 Why do I get less graduation in some cases than I need?
Frequent abbreviations at graduation
OD: Right eye
OI: Left Eye
AO: Both eyes
AV: Visual acuity
VL: Far / distant vision
VC / VP: Close-up view / next
VI: Intermediate vision
D or Dp: Diopters
Diopter: the unit of measurement of the refractive error
Most of the values that appear in the recipe will be determined in diopters (D or Dp). This is so because it is the unit of measurement that expresses the degree of visual defect of the eye.
The diopters indicate, in turn, the power that the lens of a pair of glasses or contact lenses must have in order to correct the visual defect and that the images that are out of focus, become clear.
Graduation glasses frame
The ophthalmologist or optician can use a frame similar to this one to refine the graduation of your sight with crystals with different diopters.
How to interpret the prescription data of glasses
If you have ever had a recipe for the prescription of glasses in your hands, you will have observed a lot of data with signs that are difficult to understand. Here we will clarify point by point each of these data so you understand well what correction your vision needs.
Sphere (ESF or SPH)
This field specifies the diopters or necessary power of the lens to correct hyperopia or myopia. If the values appear in positive (+) we are talking about a hyperopia whereas if they appear negative (-) we are in front of a myopia. These problems are associated with poor near and far vision respectively and the higher the value in diopters, the worse the quality of the vision without correction.
Cylinder (CIL or CYL)
The value of the cylinder, if it appears, indicates the diopters necessary to correct the astigmatism that occurs when the eye has two different graduations due to a non-spherical cornea. This data can be positio (+) or negative (-) depending on whether it is a hypermetropic or myopic astigmatism and is accompanied by another data in the form of an axis in sexagesimal degrees, that is, between 0º and 180º, which is where find the astigmatism.
It is by this last fact that, although two people have the same astigmatism diopters, they do not see well if they exchange their glasses having different axes.
At this point the information is “mixed” a little and it gets complicated but do not suffer, let’s make it clear. This data are positive diopters, such as hyperopia, but in this case are those of presbyopia or eyestrain and should never be confused because they are not the same.
The addition indicates the diopters that are added to those of nearsightedness or farsightedness to see properly up close when there is tired eyesight. It is used when you are going to buy glasses close up or when you are going to use bifocal or multifocal glasses.
As a curiosity, a myopic of -2 with an addition of +2 you just have to take your glasses away to see well up close as myopia compensates for the tired sight. You can know more about this in this article.
Visual acuity (AV)
This measure is, if possible, the most important because it speaks of the quality of vision with respect to what is considered “normal” statistically.
The values of visual acuity can be reflected as a percentage (120%, 100%, 50% …) or in decimal form (1.2, 1.0, 0.5 …). A normal vision is one that reaches the value of 100% or 1.0. There is a frequent scale in Anglo-Saxon countries (Snellen scale) where VA is shown as a fraction. An AV of 20/20 would correspond to 100%.
Visual acuity is measured without correction (AVsc) to assess the quality of our vision without glasses and with correction (AVcc) to see the improvement we obtain with optical correction.