General Glossary

• Accommodation

  The ability of the eye to focus on objects situated at various distances thanks to the crystalline lens.

• Amblyopia

  The deterioration of visual acuity of one eye due to an eye illness or an eyesight disorder not treated during childhood.

• Ametropia

  An eyesight disorder preventing the restitution of a clear image on the retina, such as short-sightedness, astigmatism or long-sightedness.

• Astigmatism

  An eyesight disorder most often due to an irregular curvature of the cornea, giving a distorted vision of far or near objects.

• Binocular vision

  The brain's capacity to form one image from the two images perceived by the two eyes.

• Cataract

  The gradual opacification of the crystalline lens, entailing a decrease in visual acuity and vision of colours. It can easily be operated on.

• Colour-blindness

  An abnormality in the vision of colours most commonly detected because of confusion between red and green.

• Contact lenses

  Small transparent domes (soft or hard) applied to the cornea, adapted to the visual fault of each wearer to correct his eyesight.

• Convergence

  The eyes'ability to simultaneously fix on the same point.

• Cornea

  Membrane which envelops the eyeball : it filters the light rays reflected by the objects we see.

• Crystalline lens

  The constituent element of the eye situated behind the iris: it helps light rays reflected by the objects we see converge unto the retina, focusing.

• Dioptre

  The unit of measurement characterising the value of an eyesight disorder, as well as the power of the lens to correct it.

• Dyschromatopsia

  An abnormality in the vision of colours characterised by difficulty in making out red, green, blue. For red, it is also called colour-blindness.

• Eye tiredness

  A visual discomfort characterised by eye stinging, eye dryness, blurred vision or red eyes, sometimes associated with headaches. It can be caused by lengthy work on the screen.

• Eyeball

  The eye and the muscles allowing it move in all directions, as a whole.

• Iris

  The constituent element of the eye surrounding the pupil: it masters the dilation of the pupil according to the intensity of light rays reflected by the objects we see and our emotions. Besides, the iris gives the eyes their colour.

• Long-sightedness

  An eyesight disorder due to a too-short eye ensuring better vision from far off than from near.

• Ophthalmologist

  The physician specialised in the treatment of eyes diseases and disorders. and in the correction of eyesight disorders, He conducts exams, delivers therapeutic or technical prescriptions and can also perform operations surgery.

• Ophthalmologist

  The physician specialised in the treatment of eyes diseases and disorders. He conducts exams, delivers therapeutic and can also perform surgery.

• Optic nerve

  The nerve linking the retina of each eye to the brain to which it transmits the image received by the retina in the form of nerve impulses.

• Optometrist

  He is the primary health care practitioner who provides non surgical eye care, including refraction, diagnosis and management for eye diseases and vision disorders.

• Presbyopia

  An eyesight fault due to the natural ageing of the crystalline lens, appearing most often towards the age of 40. As the crystalline lens loses flexibility, it no longer ensures satisfying accomodation, which entails difficulty in seeing near.

• Pupil

  The constituent element of the eye, situated in the middle of the iris: it is the opening by which light rays reflected by the objects we see get in. It constricts or dilates according to their intensity.

• Retina

  The constituent element of the eye placed at the far side of the eye. Light rays from the objects we see are projected on this membrane once they have entered the eye. The image is formed upside-down on the retina: colours, shape, details� The retina transforms this information into nerve impulses to transmit them to the brain (which will put the image the right way round) through the optic nerve.

• Short-sightedness

  An eyesight disorder due to a "too long" eye ensuring better vision from near than from far off.

• Strabismus

  An abnormality of binocular vision characterised as one eye or both deviating: they do not look in the same direction.

• Ultraviolet (or UV) rays

  Rays invisible to the human eye, emitted by the sun or by an artificial source such as a sun lamp. There are 3 categories of UV rays: UVC, UVB and UVA. The danger they represent for the eyes can be avoided by wearing sunglasses.

• Visual acuity

  The capacity to make out very fine details. It is measured in feet, meters or decimal. The average visual acuity is between 10/10 (20/20 ; 6/6) and 12/10 (20/16 ; 6/4,8).

• Visual cortex

  The part of the brain dedicated to vision.

• Visual field

  The part of the space that can be made out by the fixed eye. It can be measured for each eye or for binocular vision.