Learn more about your vision, glasses, prescription with a simplified lexicon

For a French version, please click here


Artificial material, mainly used to make glasses frames.

Addition or Add:

On the prescription, the mention "Add" is used when the patient can't see from a long distance and also needs his glasses to read. Mainly used for the close up. 

Anti-reflective coating or Anti-glare coating:

A thin transparent foil, coated on the surface of a lens, which increases 
the transmission and reduces reflection. 


Imperfection in the curvature of the cornea. 


The axis number helps the optician to adjust any cylindrical power in your glasses (this only applies for people with astigmatism).

Base curve:

Curve's type :  flat, median or steep. 

Blink reflex:

The automatic reflex of the eyelid when an object is approaching quickly.

Cat-eye frames:

An eyewear's shape within curved to the top of the frame. Which creates the cat eyes effect.

Cellulose acetate:

Artificial material, mainly used to make the glasses frames.


This indicates the amount of lens power for astigmatism. The lens power added, is not spherical but it's shaped so one meridian has no added curvature.


Part of an eye exam,  the optician is able to see more of the eye including the back of the eye and also spot any diseases. The pupil dilation is achieved after the doctor applies a specific kind of eyedrops that helps keep the pupil open. 


A unit of mesure out of the reflective power of a lens. 

Expiration date:

Time when the prescription is no longer valid. This usually lasts 2 years. 

Eye drops:

A liquid medicine, to drop on eyes. 


Short hairs at the edge of your eye. Their purpose is to protect your eyes from dust and bacterias. 


Seing objects at a distance better than the ones nearby.


Structure that hold glasses together. These can be manufactured in different shapes, sizes and colors.

High-index lenses:

Type of glasses made whit the minimum of thickness, for a top thinness and better looking. 


Eye condition meant to make appear near-by objects blurry and far's clearer.

Keyhole bridge:

Space in the middle of the frame to rest your glasses on.


Round single glass, used back then to see clearlier. 


Eye condition meant to focus parallels rays in front of retina. Objects are seen distinctly only from close.


Close vision only.

Nose bridge:

space between each lens to drop the glasses on. 

Nose pads:

Silicone pieces meant to hold the glasses and protect your nose from any damages. Usually used when the frame is made out of metal.

OD or Oculus Dexter:

Right eye


Person who makes and/ or sells glasses with prescriptions. This person is not authorized to pass eye exams. 


Someone in charge of examine people's eyes.


A doctor who treats eye diseases.

OS or oculus sinister:

Left eye


Term used when talking about a pair of glasses that do not contain any curvature and any correction. 

Polarized lenses:

Lenses that contain a specific kind of chemical that reduces glare. Mostly used to protect the reflection when the sun is reflecting on the water. 


Flexible chemical composite and very strong. Easy to use to make glasses. 


Medical document, indicating the right correction. 


Optical flat element that retracts the light. 

Progressives or bifocal:

Lenses meant to get multiple visions within one glass. You can have a clear vision far or nearby.


Circular black area in the middle eye, where the light comes in. 

Pupillary distance:

The distance between both pupils of your eyes. 


Glasses used only to see from very nearby, and to read.


Reaction that causes the light to bend when it's getting in the lenses. 


Back area in the eye that receives the light and communicate directly the information to the brain. 

Segment height:

Space from the bottom of the lens to the top of the bifocal lens.

Single-vision lenses:

Contrary to progressive lenses, the single vision lenses are used only to see from either far away or nearby. 


Lens power prescribed to correct nearsightedness or farsightedness. Could be read as a positive or a negative.   


Glasses used to protect from the sunlight and UV. Could contain prescription (to help you see better) or could also be plano (no prescription).

Temple (arm):

Long arms on the sides of the frame that extent from the hinge and over the ears to keep the glasses on the wearer's face. 


Strong chemical material used to make the frames. 


A mix of two colors that creates an effect of splattered spots. 

Ultraviolet light (UV light):

Electromagnetic radiation that is usually produced by the sun. Can be dangerous for eyes when they're exposed for too long. 

Visual acuity:

The ability of the organ to detect detail. Usually measured by reading letter from different sizes on a wall. 

Visual field:

The complete area seen when the eye is facing forward.