A Glossary of Contact Lens Terms and Definitions Ė Seeing is Believing
So you want to order contact lenses? Youíve done your research and now you find yourself knee-deep in optometric jargon. How can you see eye-to-eye, so to speak, with your optometrist and feel confident that youíre going to get the best contact lenses to suit your lifestyle? Our purpose here is to provide you with the most relevant information, in the simplest terms. So letís look at some of those contact lens terms and make some sense out of them.
An aspheric lens is a bifocal lens that changes power gradually, from the center to the edge of the lens.
Astigmatism is a condition caused by an irregularly-shaped cornea, which results in light images focusing on two separate points in the eye, creating a distorted image.
- Bifocal/Multifocal Contact Lenses
Bifocal contact lenses have two viewing areas (multifocal lenses have more than two). Part of the lens is for seeing distances and another part is for seeing up close.
- Contact Lens
A contact lens is a thin plastic lens that fits over the cornea and corrects an error in someoneís sight.
The cornea is a transparent surface that covers the pupil and iris (like a watch crystal), providing most of the eyeís optical power.
- Crystalline lens
The crystalline lens is a transparent structure that hangs behind the iris. It focuses light rays on the retina and changes shape, thus changing the eyeís focus for different distances.
- Daily-Wear Contact Lenses
Daily-wear contact lenses are designed to be worn only during waking hours, then removed, disinfected and stored for the next dayís use.
- Disinfecting Solution
A disinfecting solution kills surface bacteria and microorganisms on contact lenses.
- Disposable Contact Lenses
Disposable contact lenses are used one time and discarded.
- Extended-Wear contact Lenses
Extended-wear contact lenses are a type of disposable contact lenses designed to be worn round-the-clock for one to seven days.
- Frequent and Planned Replacement Contact Lenses
Frequent and planned replacement contact lenses are replaced on a planned schedule, for example, every 2 weeks, every month or every 3 months.
- Hyperopia (Farsightedness)
Hyperopia is the result of either an eyeball thatís too short from front to back, or a weak focusing mechanism which causes light to focus behind, rather than on the retina. The result is that people have trouble seeing objects up close. Contact lenses or glasses may be required for people with moderate to severe hyperopia.
The iris is the round membrane surrounding the pupil of the eye. The muscles of the iris adjust the size of the pupil to regulate the amount of light entering the eye.
- Myopia (Nearsightedness)
Myopia is the result of either an eyeball thatís too long, or a too powerful focusing mechanism which causes light rays to focus in front of the retina. The result is that people have trouble seeing objects in the distance.
- Ophthalmologist (MD)
An ophthalmologist is a medical doctor who diagnoses and treats all disorders of the eye, including medical, surgical and optical.
An optician manufactures and dispenses eyeglasses and helps in the selection of frames. Some are licensed to dispense contact lenses as well.
- Optometrist (OD)
An optometrist diagnoses and treats eye health and vision problems. An OD can prescribe glasses and contact lenses, and engage in low vision rehabilitation and vision therapy. An OD also can prescribe ophthalmic medications and perform certain surgical procedures.
- Oxygen permeability
Oxygen permeability refers to the amount of oxygen diffusing through a given amount of lens material in a given amount of time.
The retina is the thin nerve tissue in the back of the eye that receives an image from the lens and transforms it into an electrical impulse thatís carried by the optic nerve to the brain for interpretation.
- Rigid Gas Permeable Lenses (RPGs)
RPG contact lenses, also called oxygen permeable contact lenses, are made of a durable plastic that transmits oxygen. RPGs donít contain water so they resist deposits and donít harbor bacteria.
- Saline solution
Saline solution is a sterile salt solution thatís used for cleaning, rinsing and sometimes storing contact lenses.
- Therapeutic contact lenses
Therapeutic contact lenses help to protect and heal a sick eye.
- Toric Lenses
Toric contact lenses correct astigmatism by bearing two different optical powers at right angles to each other.
- Visual Acuity
Visual acuity is the figure that describes a personís quality of vision. Itís expressed as a fraction, for example, 20/20 vision, with the numerator being the testing distance and the denominator being the distance at which a person with normal eyesight can read the letters on an eye chart.
Simple, huh? If you feel youíve got a good understanding of contact lenses now, then this glossary of contact lens terms has done its job. Youíll know what the optometrist means when heís describing your new contact lenses to you. And youíll be able to comfortably and confidently see your way clear.
About The Author
Gareth Marples is a successful freelance writer providing valuable tips and advice for consumers purchasing bifocal or progressive contact lenses, wanting to find Gucci, Adidas, Versace designer sunglasses and even digital camera lenses. His numerous articles offer moneysaving tips and valuable insight on typically confusing topics.
This "Glossary of Contact Lens Terms & Definitions" reprinted with permission.
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