How to read an eye prescription

Have you tried to read an eye prescription but didn't understand anything? No problem, it's not as complicated as it seems, you just need some knowledge.

Generally, eye care prescriptions are divided into:

– right eye (OD)

– left eye (OS)

– far away

– for close

as you can see from the diagram on the side.

PHASE 1

In this phase we do not take into consideration the two semicircles at the top, but only the data of the part relating to the RIGHT EYE in the "FOR FAR" line.

– you are nearsighted if the value indicated in the SF (sphere) box has a – sign;

– you are HYPERMEtroPE if it has a + sign;

– if it is empty or 0 you are EMMEtroPE (it's not a bad word, it just means you have no flaws).

The number after the sign is the gradation that the lens has: the higher it is, the greater the defect you have.

PHASE 2

Now let's move on to the box marked with the CIL (cylinder) sign: if there is any value it means that you are ASTIGMATIC.

– It is MYOPIC ASTIGMATISM if the SF and CIL values are both –;

– It is HYPERMEtroPIC ASTIGMATISM if the signs are both +;

– If the signs of the figures in the SF and CIL boxes are different, it is almost always called MIXED ASTIGMATISM.

All clear? Are you still there? Then let's go to the next step.

PHASE 3

If the CIL box contains a figure then there will also be a value for the AXIS .

This value can range from 0 to 180 degrees and indicates the orientation that the lens must have to work well.

The required degrees are graphically indicated on the two semicircles that we left out earlier. A lens of correct prescription but poorly positioned does not correct astigmatism well.

For the left lens we proceed in the same way as for the right, and the values can naturally differ from one eye to the other.

PHASE 4

Correction CLOSE UP view.

These values concern subjects who present defects of PRESBYOPIA .

The term ADD (addition) will appear on the prescription, which indicates the addition of positive diopters to the lenses, to be added to any correction for distance vision.

The addition value for presbyopia concerns only the sphere, it is normally the same for both eyes and is always positive even if the resulting value can be negative.

Let's take an example: from a distance you have -4.00 while your addition is 1.50: the suitable lens will be -2.50. However, if from a distance you have +2.00 and your addition is 1.50, the suitable lens will have a value of +3.50.

As regards the PERMANENT correction values, they almost always have the same indications as those for distance.

That's all. Now you are ready to read your prescription!