Contact lens terms │ Glossary

Sometimes we will use medical or technical terms to explain problems with vision, and how Feel Good Contacts’ products can help. This glossary is a list of words commonly used on Our definitions should help you better understand your eyesight and your contact lens prescription.

Air bubbles A bubble of air formed inbetween the eye and the contact lens. Air bubbles can be caused by improper application of a lens or a poor fit of lens.
Allergy sufferer A person who suffers from a physical intolerance to a substance. Contact with the substance can cause discomfort, itching, redness and inflammation.
Astigmatism A distortion of vision caused by a cornea that does not curve equally in all directions.
Axis An axis indicates the direction of the curve needed to correct astigmatism. It will be a number between 0-180.
Base curve A measurement of the curvature of the contact lens. Always done in millimetres, this figure determines how well a contact lens will fit the eye.
Coloured lens A pigmented contact lens designed to alter the perceived colour of the wearer's iris. They can be prescription or non-prescription.
Eye drops An eye drop which soothes and lubricates sore, dry eyes.
Conjunctivitis A condition that causes redness and inflammation to the thin layer of tissue covering the whites of the eyes.
Contact lens A curved, plastic lens applied to the surface of the eye to correct visual defects.
Cornea The clear, outermost layer of the eye, covering the pupil and the iris.
Cylinder A number which defines the level of correction needed for astigmatisms. It is sometimes represented as CYL, and is always a minus figure.
Daily disposables Single-use contact lenses. These lenses are worn for one day only, and then discarded.
Diameter The width of a contact lens measured in millimetres.
Enzyme cleaner This is used for removing protein from contact lenses. It comes in tablet form and is dissolved in solution before use.
Eye dryness When the eye is not kept sufficiently lubricated by tears and becomes dry and painful. Can be caused by long term contact lens wear.
Eye solution A liquid which is safe to use on items which come into contact with the eye. This includes disinfectants, storants and cleaners.
Hard lens Hard lenses are Rigid Gas Permeable. They are smaller and longer lasting than soft lenses, do not contain water and resist bacteria well.
Hydrophilic material Soft lenses are made from this material. It has properties which cause water to spread evenly across it's surface. Hydrophilic means 'water loving'.
Hyperopia This is a term used to describe long-sightedness.
Intensive protein cleaner A cleaning solution designed to remove excess protein from contact lenses.
Iris The coloured part of the eye, surrounding the pupil.
Irregular astigmatism A distortion of vision caused by a cornea which curves irregularly in several directions.
Lacreon technology A technology that embeds a water-holding ingredient, similar to what is found in natural tears, into the contact lens material.
Lens A clear, almost spherical body inside of the eye. It focuses light on to the retina.
Lens fitting Usually performed by an optometrist, this is an appointment to find out the correct shape and size contact lens for an individual's needs.
Long-sightedness When a person can see distant objects clearly, but struggles to focus on nearby objects.
Macular degeneration A pain-free medical condition. Often age-related, it causes your central vision to become blurred.
Multifocal lens A contact lens with several different focal powers.
Myopia This is a term used to describe short-sightedness.
Opthalmologist A fully trained doctor, specialising in treatment of the eye.
Optic nerve This nerve connects to the eyeball, and transmits images from the retina to the visual cortex.
Optician An individual who dispenses eye wear. Able to perform contact lens fitting and determine necessary prescription.
Optometrist An individual fully trained and qualified to examine your eyes, detect conditions and visual difficulties – they are able to prescribe for eye conditions.
pH of healthy tears pH is a measurement of the acidity or alkalinity of a substance. The pH of normal tears is neutral, and falls inbetween 7.3 and 7.7.
Pigments Found in the iris, the pigment produces the natural colour of the eye.
Power This is a figure in your contact lens prescription which indicates whether you are long or short sighted.
Presbyopia The medical name for age-related long-sightedness. It is a reduced ability to focus on nearby objects.
Prescription (contact lens) This is a document issued by a trained optician or optometrist. It details the specifics required from an individual's contact lens to correct their vision.
Protein There is protein in the tears that lubricate the eye. This protein can stick to contact lenses and cause blurred vision and irritation.
Pupil The black circle in the centre of the eye. It is an opening which allows light to enter the eye.
Regular astigmatism A distortion of vision caused by a cornea which curves more strongly in one direction.
Retina A light sensitive layer of cells lining the inside of the eyeball. It receives the images produced by the lens.
Rigid gas permeable (RGB) Rigid gas permeable contact lenses are made of a plastic which transmits oxygen from their surface to the eye.
Saline solution A sterile solution. It is made from sodium chloride and water.
Sclera The scientific name for the white of the eye.
Short-sightedness When a person can see nearby objects clearly, but struggles to focus on distant objects.
Soft lens Lenses made from a soft, plastic gel (often silicone hydrogel). These lenses contain water so must be bathed in solution regularly to prevent them from drying out.
Tears Tears are made of oils, proteins and moisture. Spread by blinking, they protect the eye against infection and dehydration.
Toric lens Used to correct astigmatism, these lenses curve differently to the typical spherical lens.
Two weekly disposable Contact lenses designed to be worn during the day for two weeks and then discarded. They should be removed and bathed in solution every evening.
UV protection Materials that provide defence from harmful UV rays.
UV rays Ultra violet rays are invisible waves of radiation present in sunlight. They can cause macular degeneration, cataracts and other dangerous conditions.
Visual cortex The part of the brain which processes visual information.