Astigmatism

Astigmatism is where the cornea is irregularly shaped which causes distorted vision. This vision is especially distorted at near distances. Either glasses or contact lenses can correct this problem for most people.

Axis

The axis (measured in degrees) tells the person making the spectacles what angle to position the lens so that the two curves are in the right place in front of the eye. A prescription which has a sphere and a cyl must have an axis.

Base Curve

The base curve of a contact lens is the radius of the sphere that the back of the contact lens describes. Your eye practitioner should ensure the contact lens fits well to your cornea in order to be comfortable and to facilitate tear exchange and oxygen transmission.

Generally, if your contact lens feels lose and slides easily,a smaller base curve may work better.A larger base curve may be needed if they feel tight.

Bifocal

A type of spectacle or contact lens design that includes two focal areas: one for near, one for distance

Center Thickness (CT)

A measure of the thickness of the contact lens at its center.

Cleaning solution

This solution is used to clean your contact lenses. The solution, along with rubbing, helps with loosening any debris, which is then rinsed off with saline solution.

Color Changing

Color Enhancer: This lens changes the color of your eye completely.
Color Blends: This lens enhances the natural color of your eye.
Colorless: This lens blends three colors into one to create the subtle, natural depth of beautiful eyes.
Crazy Lenses: This is a clear lens without any color function.

Contact lens technician

In many states, contact lens dispensing may be handled by specially trained technicians, who fit the lenses after an optometrist or ophthalmologist determines the prescription.

Cornea

Clear front eye tissue that covers the iris and pupil and admits light. Contact lenses either fully or partially cover the cornea.

Daily wear lens

Worn during waking hours and removed at the end of each day for cleaning and disinfecting.

Disinfectant

This is an agent that inhibits the growth of or destroys harmful microorganisms such as bacteria.

Disinfecting/soaking solution

After cleaning contact lenses and rinsing them with saline, fill the chambers of your storage case with enough disinfecting solution to cover the lenses. Always use fresh disinfecting solution. Allow your lenses to soak and disinfect overnight.

Disposable contact lens

Worn for brief periods, from one day to two weeks, then discarded and replaced with a new lens.

Dry eye syndrome

Dry eye usually occurs when eyes don't produce enough tears or when tears evaporate too quickly because of environmental conditions.

Emmetropia

This is the term for normal vision. When the cornea and lens of the eye focus an image directly on the retina, clear vision is the result.

Enzyme cleaner

An extra-strength cleaner, typically used weekly, to remove stubborn deposits from contact lenses.

Extended wear lens

These lenses do not have to be removed for sleeping. Most extended wear lenses are worn continuously for one week. There are several brands that are approved for 30-day wear.

Farsightedness

This is a condition where the eyeball is too short and flat, so that light rays haven't yet focused when they reach the retina. The result is difficulty in seeing near objects clearly.

GP contact lens

GP contact lenses are also known as a gas permeable or RGP (rigid gas permeable). This contact lens is made of breathable plastic that has been custom fitted to the shape of the cornea. GP contact lenses are long-lasting, comfortable, easy to clean, and healthy for the eyes.

Hard contact lens

Hard contact lenses are made of an inflexible plastic material called PMMA (polymethylmethacrylate). These were the first contact lenses in wide use. Hard lenses had excellent optics, but because they kept oxygen from reaching the cornea, they've become virtually obsolete.

Hyperopia

Another term for farsightedness.

Iris Size

The Iris is the anterior part of the vascular tunic of the eye, which is situated in front of the crystalline lens and behind the cornea. It has a shape of a circular membrane with a perforation in the center (the pupil) and is attached peripherally to the ciliary body. The pupil is sometimes known as the Iris Size

Keratoconus

Keratoconus is a condition where the cornea becomes cone-shaped, causing major vision distortion. People with this condition are particularly challenging to contact lens fitters, who usually must prescribe custom-made lenses for them.

Lens Type

Single Vision: A lens in which the two surfaces are spherical.
Single Vision Toric: A toric or cylindrical lens which produces two separate focal lines at right angles instead of a single focal point
Bi- / Multi- / Trifocal: A lens which combines corrections for both distance and near vision, with a visible dividing line or curve.
Bi- / Multi- / Trifocal Toric: A lens which combines distance, intermediate and near vision in one lens but with no visible line.

Monovision

This is a contact lens fitting technique that is an alternative to bifocal glasses, bifocal contacts, or reading glasses. It may be used with either soft or GP contacts. One eye is fitted with a contact lens for distance vision, and the other eye is fitted for near vision. Although it is an effective technique, it does have disadvantages. For example, many people who use monovision report compromised depth perception.

Multifocal

A type of spectacle or contact lens design that includes more than one focal area. Bifocals and trifocals are both multifocal lens designs.

Myopia

Another term for nearsightedness.

Nearsightedness

A condition where the eyeball is too long and steep, so that light rays focus before they reach the retina. The result is difficulty in seeing distant objects clearly.

Ophthalmologist

Ophthalmologists are medical doctors (MDs) who are eye specialists. They perform eye examinations, treat disease, and perform surgery; some also specialize in contact lenses. In some states ophthalmologists may have opticians and contact lens technicians working with them, who are specially trained to fit contact lenses.

Optician

Opticians and contact lens technicians are not doctors. In some states they can become certified, after special training, to fit contact lenses. Some specialize in contact lenses and work in optometric or medical offices, working as a team with an OD or MD to fit contact lenses.

Optometrist

Doctors of optometry (ODs) complete four years of post-graduate optometry school. Optometrists examine eyes for both vision and health problems, prescribe glasses, and fit contact lenses. They can prescribe many ophthalmic medications and often participate in pre- and post-operative care.

Orthokeratology (ortho-k)

A non-surgical procedure for changing the shape of the eye's cornea. The procedure involves wearing a series of GP contact lenses that progressively "mold" the surface of the cornea into a shape that provides for better vision. The procedure does not have a permanent effect. Therefore, just as orthodontic retainers keep your teeth from moving back to their original positions, "retainer" contact lenses must be worn periodically to keep the cornea from regressing back to its less desirable shape.

Presbyopia

The age-related inability to focus clearly at all distances. Presbyopes may wear reading glasses, multifocal contact lenses, or glasses.

Progressive addition lenses

Like bifocals and trifocals, progressive lenses provide clear vision at all distances: near, intermediate, and far. The difference is that the viewing zones gradually blend into each other, for lenses that are more attractive to wear.

Pupil

The pupil is the small dark portion in the center of the eye. It opens and closes to regulate the amount of light, and thus the amount of visual information, the retina receives.

Pupil Size

The Pupil Size is the size of the "hole" in the middle of the color changing iris part of the lens where you can look through. It is important that this size is big enough so that you can see enough.

Refraction

A measurement of the eyes to determine the level of visual acuity. Most refractions are performed by optometrists, though many ophthalmologists do them as well. Refractions often result in a prescription for glasses or contact lenses.

Retina

Thin tissue in the back of the eye that receives an image formed by the lens and converts it to electrical impulses carried by the optic nerve to the brain.

Rewetting solution

Drops that contact lens wearers can use all day if needed to keep the eye moist.

RGP contact lens

Abbreviation for rigid gas permeable lens. Same as GP (gas permeable) contact lens.

Saline Solution

Sterile salt solution used to clean and store soft contact lenses. Saline is also used to rinse both soft lenses and GP contacts.

Shape

There are just two different shapes in the contact lens market.http://www.london-eyewear.co.uk/img/t.gif They are spherical and elliptical.

Soft contact lens

Made of gel-like plastic, soft contact lenses contain varying amounts of water. They provide good initial comfort for first-time wearers but must be replaced often.

Toric contact lens

A contact lens design for correcting astigmatism.

Total Diameter

Total Diameter (TD, DIA) tells you how big the contact lens is.

Trifocal

A type of spectacle or contact lens design that includes three focal areas: usually a reading lens, a lens for faraway viewing, and a lens for mid-distance viewing.

Trifocal

A type of spectacle or contact lens design that includes three focal areas: usually a reading lens, a lens for faraway viewing, and a lens for mid-distance viewing.

UV Inhibitor

A contact lens which has a UV-inhibitor helps protect against transmission of harmful radiation to the cornea and into the eye.

Wetting solution

Drops used to ease the process of applying a GP lens to the eye. Wetting solution may also be used to relieve dryness after several hours of lens wear.

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