Eye care practitioners
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    • Glossary

    Glossary

    Not sure what a word means?

    Check out this glossary of eye and contact lens related terms.

    • A-E
    • F-J
    • K-O
    • P-U
    • Accommodation

      The ability of the natural crystalline lens to adjust and - with the natural contractions of the muscle in the eye - focus on objects through a range of near, intermediate and far distances.

      Accommodating intra-ocular lens

      As with the natural lens, an accommodating lens moves and flexes, in response to ciliary muscle contractions in the eye. These contractions drive forward movements of the lens so the eye can maintain a clear image as it focuses on near, intermediate and far objects.

      Crystalens® is the first and only accommodating lens approved by the FDA.

      Age-Related Macular Degeneration (pronounced mak-you-lar dee-jen-er-ei-shun) (AMD)

      An eye condition in which the centre of the retina (the macula) is slowly damaged, affecting central vision.

      Amsler Grid

      A chart of grid lines and a central dot used to find and check problems with central vision.

      Antioxidants

      The nutrients that neutralise and deactivate free radicals.

      Aspheric

      In relation to spectacles and contact lenses refers to the shape/design of the lenses; not quite spherical. Aspheric spectacle  lenses are popular among people who have strong prescriptions because they are thin and lightweight, and reduce distortion and eye magnification.

      Aspheric contact lenses can enhance optical design that creates crisp, sharp vision beyond what you are likely used to -designed to reduce halos and glare - especially at night and in low light.

      Astigmatism

      A condition in which the cornea is irregularly shaped, which prevents light rays from focusing so that near and distant objects appear blurred or distorted. Glasses and toric contact lenses (gas permeable and soft lenses) can correct astigmatism.

      Cataracts

      A clouding of the lens inside the eye so that light cannot get through to the retina.

      Conjunctivitis

      Inflammation of the conjunctiva, characterized by a pink eye. The cause is either infectious or allergic, though the term "pink eye" is commonly used for any type of conjunctivitis. Other symptoms include burning, discharge, dryness, itching, light sensitivity, eye pain or discomfort, stickiness and tearing.

      Cornea

      The outer, transparent, dome-like structure that covers the eye's iris, pupil, and anterior chamber. Part of the eye's focusing system that transmits and focuses light into the eye.

      Crystalline lens

      The transparent, double convex (outward curve on both sides) structure behind the iris. The lens of the eye helps to focus light rays onto the retina.

      Daily Wear Contact Lenses

      Contact lenses that are worn during waking hours but removed at the end of each day for cleaning and disinfecting.

      Diopter

      Unit of measure for the refractive (light-bending) power of a lens; eye care practitioners use it in eyeglass and contact lens prescriptions. A negative number refers to nearsightedness; a positive number, farsightedness. For example, someone with -8.00 diopter lenses is very nearsighted, while someone with +0.75 diopter lenses is only slightly farsighted.

      Disposable Contact Lenses

      Disposable lenses refer to the replacement frequency of the contact  lenses. This can range from daily disposable, designed for single use and then discard or disposable lenses which are worn on a daily basis and then cleaned daily between use and then discarded upon Eye Care Professional's advice, often 2 weekly or monthly

      Dk/t

      Dk/t is a measurement used to quantify the amount of oxygen that is transmitted through the contact lens. The higher the Dk/t value; the higher the amount of oxygen transmitted through the lens.

      Extended Wear Contact Lenses

      Contact lenses that have been approved for overnight wear.  Extended wear contact lenses are typically approved for up to 7 days/nights of overnight wear or up to 30 days/nights of overnight wear between removals for cleaning and disinfection or disposal.

    • Foreign body

      Something in or on the eye that doesn't belong there. Symptoms include foreign body sensation, eye pain or discomfort, a red or pink eye, tearing, frequent blinking, blurred vision, discharge, light sensitivity and vision loss.

      Frequent/Planned Replacement Contact Lenses

      Contact lenses that are worn on a daily basis and are cleaned, rinsed and disinfected each time the lens is removed. The lenses are discarded after the recommended wearing period prescribed by the eye care professional.

      Gas Permeable (GP) Contact Lenses

      A type of contact lens that is made of a breathable, firm, durable, plastic that is custom fitted to the shape of the cornea.

      Hard Contact Lenses

      The first widely used type of contact lens, which was made of an inflexible plastic material called PMMA (polymethyl methacrylate). Although they provided excellent optical correction, hard lenses did not allow oxygen through the lens to reach the cornea.

      Hyperopia (also far or long-sightendness)

      A condition in which the eye is too short and flat, thereby preventing light rays from focusing before reaching the retina. This causes an inability to see near objects clearly.

    • Lens (also crystalline lens)

      The transparent, double convex (outward curve on both sides) structure behind the iris. Lenses help to focus light rays into the retina.

      Lipid

      Organic compound that is oily, fatty, or waxy and commonly found in living cells. Lipids are one component of human tears, forming an oily outer layer that helps keep the eye moisturized by reducing evaporation of the watery and mucus layers beneath it. Lipids can collect on contact lenses, making them uncomfortable.

      Macula

      The part of the eye responsible for detailed central vision.

      Monofocal

      Type of spectacle lens, intraocular lens (IOL) or contact lens design that has only one area for the eye to focus through

      Multifocal

      Type of spectacle lens, intraocular lens (IOL) or contact lens design that includes more than one area through which the eye focuses which allows people with presbyopia to see at multiple distances.

      Myopia (also Near or short-sightedness)

      A condition in which the eye is too long and steep, thereby causing light rays to focus before reaching the retina. This causes an inability to see distant objects clearly.

      Optic Nerve

      The nerve at the back of the eye that carries visual impulses from the retina to the brain.

      Ophthalmologist

      A medical doctor who specializes in diagnosing and treating eye disorders. They perform eye exams, treat disease, prescribe medication, and perform surgery. They may prescribe glasses and corrective lenses. In some states, ophthalmologists may have opticians and contact lens technicians fit contact lenses.

       

      Orthokeratology

      Treatment for corrections, such as myopia, in which the patient wears gas permeable lenses to reshape the cornea in order to be able to see temporarily without vision correction.

    • Presbyopia

      A condition associated with aging in which the normally soft and flexible crystalline lens of the eye hardens and becomes less elastic, making the lens less able to focus incoming light, thereby causing blurred vision at reading distance. Can be corrected with bifocal or multifocal contact lenses or glasses.

      Protein

      Large, complex organic molecules found in all living cells. These molecules contain enzymes, antibodies, hormones and other elements that help organisms function. Proteins are present in human tears and can collect on contact lenses, resulting in discomfort and cloudy vision.

      Refraction

      The test performed during an eye exam to determine the eyeglass lens powers needed for optimum visual acuity. An automated refraction uses an instrument that does not require the patient to respond. A manifest refraction is the manual way to determine the best lenses, by placing various lenses in front of the patient's eyes and asking, "Which is better, lens A or lens B?"

      Retina

      The light-sensitive layer of tissue that lines the inside of the back of the eye. The retina translates the optical image into neurologic impulses that are transmitted through the optic nerve to the brain.

      RGP

      (Rigid Gas Permeable) Type of contact lens made of breathable plastic that is custom-fit to the shape of the cornea. RGPs are the successor to old-fashioned hard lenses, which are now virtually obsolete.

      Soft contact lenses

      Contacts made of gel-like plastic containing varying amounts of water

      Spherical

      A contact lens design that is like a sphere and is fairly common; in contrast, toric lenses for astigmatism are football-shaped and are less common.

      Sty

      A small red bump on the edge of the eyelid caused by an infected gland. Additional symptoms include eyelid pain, eyelid swelling, eye pain or discomfort, foreign body sensation, light sensitivity and tearing.

      Toric

      A lens design with two different optical powers at right angles to each other for the correction of astigmatism.

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