What is myopia and hyperopia?
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Myopia is whaen you are short sight sighted. ( ie you can see at near but not far).
Hyperopia is when you are long-sighted. (ie you can see far but not at near).
I have just had a cataract operation and need a corrective prescription. Can i use contact lenses?
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There can be no problems as long as enough time has elapsed between your cataract operation. This is usually about two months. Ideally, your ophthalmologist at the hospital should recommend this.
How has the history of contact lenses progressed?
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The history of the contact lens includes some remarkable people, Leonardo da Vinci among them. It is an amazing history, beginning in 1508 and still continuing with advances today. Explore this amazing timeline.
1500’s Leonardo da Vinci first explores the concept of contact lenses. He explained how immersing the eye in a bowl of water could change the power of the cornea. Leonardo sketches several forms of contact lenses.
Mid 1600’s Rene Descartes suggests that corneal contact lens can be used to correct eyesight. His idea describes using a glass tube filled with liquid, with an end made of clear glass. The tube was to be placed directly over the cornea. The idea worked in theory, but not practicality. The tube prevented blinking.
1801 Thomas Young expands on Descartes’ idea. He designs a quarter inch glass tube filled with water fitted with a microscope at the outer end. Young uses this device to correct his own vision. Young’s invention did not correct the problems of light refraction.
mid-1800’s Sir John Herschel suggests two important ideas. The first is a sphere of glass filled with animal jelly. The second involves making a mold of the eye to fit the sphere exactly on the eye surface.
1887-1888 Adolph Fick explains how afocal scleral contact “shells” can be placed on the less sensitive part of the eye. These workable lenses are made of heavy blown glass and cover the entire eye. The space between the glass and the cornea is filled with a sugar solution. In this same time period Muller develops a more comfortable glass blown scleral lens.
1929 Dr. Dallos uses Herschel’s idea of taking a mold of the eye.
1936 William Feinbloom uses Plexiglas ( polymethyl methacrylate) to make a plastic scleral lens. The center is made out of glass and the outer band is made of plastic.
1945 The American Optometric Association recognizes contact lenses as an important part of the field of optometry.
1948 Kevin Touhy begins making contact lenses entirely of plastic. These still cover the entire cornea. This same year, Dr George Butterfield designs a lens that sits better on the eye.
1960 Otto Wichterle experiments with a soft water absorbing plastic to make contact lenses. These soft contact lenses are much more comfortable.
1971 Soft contact lenses are approved by the US FDA and become commercially available through Bausch and Lomb.
1978 The first toric contact lenses are approved for distribution.
1979 The first rigid gas permeable (RGP) contact lenses are made and silicone- acrylate lenses are sold.
1980’s-1990’s Oxygen permeable materials or polymers are developed through out this time period. Tinted daily wear soft lenses, extended wear soft lenses, bifocal daily wear soft lenses, tinted RGP, extended wear RGP, disposable soft contact lenses, multi-purpose lenses, planned replacement lenses, daily wear two-week extended replacement lenses, all became available during this time period.
1999 Silicone hydrogels become commercially available, offering extreme comfort.
What are silicone hydrogel lenses and how do they work?
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A new generation of "super-permeable" contact lenses can transmit unprecedented amounts of oxygen to your cornea and, in some cases, enable 30 consecutive days of wear without removal
Silicone hydrogel contact lenses represent a breakthrough over traditional hydrogel soft contact lenses, because silicone lets so much oxygen (essential for a healthy cornea) pass through the lens. "We're talking about lenses that breathe six to seven times more oxygen than previous lenses," says P. Douglas Becherer, OD, former chairman of the American Optometric Association's Contact Lens and Cornea Section.
Silicone hydrogel contact lenses have caught on with both wearers and eye care practitioners. By 2009, silicone hydrogel lenses are expected to account for more than two-thirds of U.S. soft contact lens sales (in dollars), according to equity research firm Robert W. Baird & Co.
How Silicone Hydrogel Lenses Work
Traditional soft contact lenses are made from hydrogel polymers (soft, water-containing plastics). The plastic itself is not oxygen permeable, so the water performs the job of carrying oxygen through the lens to the eye. But water can carry only so much oxygen — and the more water a lens contains, the greater its tendency to dehydrate after long periods of wear.
Silicone is oxygen permeable. So silicone hydrogel lenses use both their water and polymer content to transmit oxygen to the eye.
The benefits to wearers include comfort and convenience:
Silicone hydrogel contact lenses contain less water than traditional hydrogel lenses. As a result, they aren't as prone to dehydration while you're wearing them. For some people who wear their lenses for long days, this can mean better end-of-day comfort.
Silicone hydrogels also have made 30-day contact lens wear — sometimes called "continuous wear" — available once again.
What is presbyopia?
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Presbyopia is a natural condition that occurs as the eyes age. Basically, the lens of the eye begins to become less flexible and so focusing on near objects becomes a problem. This has no bearing on your distance acuity. Its like comparing a camera with a zoom lens with the batteries running out! The zoom takes longer and harder to focus. However, presbyopic lenses are now available to offer some relief on this problem. They are termed as "presbyopic" or "bifocal" lenses.
What are extended wear lenses?
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Purevision by Bausch & Lomb and Air Optix Night & Day are examples of this type lens. Also see "Silicone Hydrogel Lenses".
Extended wear (continuous wear) contact lenses are made to be worn over night for several days. This is possible due to the high oxygen flow, through the lens to the eye, allowed by the revolutionary material they are made from. What is this revolutionary material? Among other things - water. Actually, the high water content in other types of contact lenses inhibits oxygen flow, but in the specially designed extended wear lenses it increases oxygen flow. The types of extended wear lenses are defined by the amount of water in them.
TYPES OF EXTENDED WEAR LENSES
Low water content lenses. These have a water content of 38%-45%. These are thin and can be difficult to work with.
Medium water content lenses. These have a water content of 48%-69%. These are the most popular choice among contact lens wearers.
High water content. These have a water content of 70%-80%. They allow for the most oxygen flow, but can have increase deposits on the lenses.
Extended wear contact lenses are very beneficial. They are more convenient. There is no worrying if you fall asleep at work or at school, when you didn’t expect to. They are particularly beneficial for those people whose eyesight is such that they have difficulty seeing in the morning when their contacts are not in. These patients have the wonderful experience of waking up and seeing well, right away. Something many people take for granted. Also given the increase oxygen flow there are fewer eye infections with extended wear lenses.
There are some complications, however. Because they are worn continuously, they can lead to dry eyes causing discomfort. While it was previously stated that there area fewer infections there are some organisms that thrive in the environment. Also the occurrence of corneal ulcers is the same for extended wear users as the users of regular contact lenses.
Extended wear contact lenses made from silicone hydrogel have been introduced to help combat some of the problems with extended wear lenses. They are certainly an improvement, but more advances are needed. With improved lens design, and better cleaners and disinfectants, problems for extended wear contact lens users will continue to decrease.
The patient can improve their own chances for decrease complications by avoiding smoke and swimming with the lenses in. Obviously, if smoke or pool chemicals get between the lens and the eye problems will occur. Also strictly following doctor’s recommendations greatly improves your chances of successful extended wear contact lens use.