How to read a lens prescription

Before anything else, we're going to talk about the validity date of a contact lens prescription, it has moreover been modified since the decree appeared in October 2016.

First and foremost, it's important to know that a prescription is mandatory for a first fitting, then the validity depends on the individual's age:

-1 year for people under the age of 16

-3 years for people over 16, unless otherwise specified on the prescription.

Of course, these figures are generic, and the ophthalmologist may revise them downwards if necessary.

In addition to your correction, your prescription contains a number of other items of information:

-Information specific to your practitioner, such as his or her name and ADELI number. What is the ADELI number? It's a 9-digit number starting with the number of the département, which immediately identifies a doctor.

-Next come your personal details, such as the date of the prescription, your date of birth, and a description of your identity. A prescription is above all personal.

-Then comes the part where the ophthalmologist establishes the type of lenses you need (which brand, which model, which option?)) It's the ophthalmologist who chooses the model, because he or she can measure the physiology of your cornea to determine which type of lens is best suited to you.

-After the type of lens comes your correction. If you also wear glasses, you may find that sometimes the lens correction differs slightly from the glasses correction.

-But what do all these different numbers and signs mean?

-The first number corresponds to the sphere. If it's preceded by a minus, it means you're myopic, and if it's preceded by a plus, you're hypermetropic. Then, the larger the number, the greater the power of your myopia/hyperopia.

-If the number is in brackets, accompanied by a degree axis, you have astigmatism.

-Finally, if there's an addition (usually the word "add") after a number between 0.50 and 2.50, it means you're presbyopic and need correction to see clearly at any distance, and therefore progressive equipment.

Example:

OD : -2.50 (+1.00 ) 25°

OG: -1.50 (+0.75) 50°

In this case, the person concerned is myopic because the first number (the sphere) is negative. It is also astigmatic, as there is a number between the brackets (called the cylinder) and an axis

We can deduce :

Sphere

for right eye: -2.50

for left eye: -1.50

Cylinder and axis

For right eye: +1.00 at 25°.

For left eye: +0.75 to 50°.

Another example:

OD: +2.00 add: +1.50

OG: +1.50 add: +1.50

In this case, we can deduce that the person is hypermetropic because the sphere is positive. The word add also appears, meaning that the person in question is presbyopic and therefore requires progressive equipment.