Friday, March 13, 2009
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Since those are inserted only once, they never need to be cleaned or sterilized at all. You just clean your hands, insert them, then throw them away after the wear period. No muss, no fuss. But, that convenience comes at a price.
Cost is a factor to consider and it's not always negligible. While prices vary over time, disposables are typically more expensive over the long run. You pay for the convenience. But the daily costs are lower, since the lens is intended to be used only for a short period.
One way manufacturers can do that, of course, is to use different materials and production methods. The result is a safe, comfortable lens but one that may not provide the same optimally sharp vision that another style can.
Still, many sports enthusiasts enjoy disposable lenses thanks to their tight fit, which results in them being very hard to knock loose. And if the quality is good enough for them, it will probably be good enough for most everyone.
Investigate your options in disposable contact lenses and you may well find one that is just right for you and your lifestyle.
Wednesday, March 11, 2009
Disposable contacts were first introduced in 1987. Since then they have become one of the most popular options for contact lense wearers. They're comfortable, safe and come in a variety of different types.
Disposables are designed to be worn and discarded either daily, weekly, bi-weekly or monthly. But it's important to keep in mind a distinction, that between the replacement schedule and the wear schedule. Some are designed to be worn daily and discarded daily. But some that are labeled dailies are removed daily, cleaned and stored, then reused up to their intended lifetime. That lifetime can be one week, two weeks, or even as long as a month. Make sure you note which is which when you choose your lenses.
The more often you change your prescription contact lenses the lower the odds of health problems. Even the best of contacts reduce the amount of oxygen that gets to the surface of the cornea. That ups the chances of infection. Longer wear cycles also increase the odds of corneal abrasion, conjunctivitis and other eye health issues.
However, changing lenses more frequently can increase the odds of introducing other kinds of health problems. For example, some preservative solutions can cause an allergic reaction to some contact lens users. Wearing a pair of disposables continuously for a week, then simply throwing them away, eliminates that possibility. They come packaged in a sterile solution, so they never need to be cleaned unless they're removed and re-inserted.
Saturday, March 7, 2009
Contemporary contact lenses are comfortable, long-lasting (unless by design, as in disposables) and very safe. Yet, there are some risks and limitations in wearing them and knowing what those are can help you choose the type that’s best for you. Of course, any such decision should be made in consultation with your eye care professional.
Since 1986 many have opted for Rigid Gas Permeable contact lenses. Modern designs allow for up to five times more oxygen diffusion through the plastic than those of the past. That feature is important in minimizing the odds of corneal infection. The less oxygen that makes it to the eye, the higher the odds of an infection.
On the downside, RGP lenses are a little less flexible than other types, making them less comfortable for some. But, they may be better for correcting astigmatism as a result. They also can last up to 2-3 years, which is longer than typical soft contact lenses.
Thursday, March 5, 2009
Modern contacts are manufactured to extremely high standards. Millions wear them daily and for years without health problems or even discomfort. Still, about 4% of all contact lens users experience some type of health issue at some point. Risks of wearing contact lenses, while very low, are not zero. Your odds can be improved by proper use, though.
One overall issue is the fact that any contact lens will restrict the amount of air that gets to the eye. That increases the odds of infection, even when lenses are well sterilized. With the popularity of 7 day or even 30-day continuous wear lenses, that problem (while small) is larger than it was in the past.
Apart from infection, discomfort and blurred vision can occur when a lens is worn for more than a few days. That irritation can occur to the eyeball itself, and also to the lens and surrounding tissues. One possible result is GPC (Giant Papillary Conjunctivitis).
GPC produces itching and redness on the surrounding tissue, the result of protein buildup on the surfaces of the lens. Swelling occurs on the interior surface of the eyelids and can produce a sticky discharge as well. When this occurs, you should discontinue use until your eye care professional declares the lenses are safe to wear again. Regular, careful lens care and proper use can reduce the odds of any re-occurrence.
Corneal abrasions, while uncommon, are also far from unknown among contact lens users. A small scratch on the clear tissue over the pupil can happen when small particles of grit get between the lens and the eye, usually as a result of poor cleaning or handling. But it can occur even to the most careful, as airborne or finger-borne material lands on the surface of the eyeball.
Knowledge can give you a real advantage. To make sure you're fully informed about contact lense , keep reading.
Hopefully the information presented so far has been applicable. You might also want to consider the following:
Small pieces of eyelash, cotton threads, airborne plant material and much more can all wind up in the eye. In the absence of contacts these things are normally washed away by the tears and eyelid working together. Contacts can interfere with that process. In many instances, antibiotics are called for since infection is common under these circumstances.
Pollen and other material can also produce allergic reactions that are sometimes amplified by contact lenses. The eyes become red and irritated and excessive tearing can occur, leading to blurred vision and discomfort. Sometimes the reaction is the result of preservatives in the lens cleaning solution. It happens more often with soft contact lenses. Treatments include removing the lens for a time, changing solutions and using different storage methods.
The contact lenses themselves can cause problems if they change shape. While rare, previously well-fitting contact lenses can be affected by temperature and age, causing tears and oxygen to less efficiently make it to the eye. This so-called Tight Lens Condition can cause pain, redness and even swelling of the cornea. Correction consists of remeasuring the eye and fitting new contacts after the eyes have recovered.
The cornea itself can change shape, as can the whole eyeball. The change is subtle, but with contact lenses the tolerances are small. If corneal warpage (as it's called) does happen the result can be discomfort and an increase in the odds of infection. The condition is more common with gas permeable and hard lenses, which are less flexible than soft contact lenses.
If this happens, healing can take weeks or months, during which time contact lenses can't be worn. As the eye resumes its normal shape, vision can change. More than one glasses prescription may be required for optimal sight. In rare cases the astigmatism is permanent.
In all cases, following the manufacturer's and your eye care professional's guidance about cleaning, insertion and removal, contact lens care and wear are your best bet to avoiding problems.
Of course, it's impossible to put everything about contact lense into just one article. But you can't deny that you've just added to your understanding about contact lense, and that's time well spent.
Sometimes it's tough to sort out all the details related to this subject, but I'm positive you'll have no trouble making sense of the information presented above.
Wednesday, March 4, 2009
The human visual system is both simple and complex. Complex, because there are so many parts that have to work together to make sight possible. Simple, because those parts and the process can really be explained without in-depth knowledge of anatomy and biology.
An ordinary glass lens, such as a magnifying glass, focuses the light that moves through it by bending the rays toward a focal point. That's the bright spot you see when you hold one over a newspaper, for example. Something similar happens when light enters the eye through an opening called the pupil, behind a clear protective portion called the cornea.
The pupil is surrounded by the iris, the colored portion of the eye. The pupil can narrow or widen to regulate the amount of light admitted, from as small as about 2mm to as much as approximately 8mm. The iris contains the muscles that change the diameter of the opening. Just behind the pupil is the lens, the part that focuses the light rays similar to the magnifying glass.
But there's an important difference between a magnifying glass and the eye. The magnifying glass's focal point is fixed. The eye, by contrast, contains muscles that help shape the lens and that shaping process performs a number of important tasks. Most importantly, it makes it possible for the focal point to change.
A camera lens is a good analogy. Because the camera lens contains multiple pieces of glass that can be moved by turning the barrel, objects at different distances can be brought into focus on the film. The muscles attached to the lens perform a similar function in order to focus light onto the retina, which is like the film.
Focused light rays strike the cells of the retina, the cones and rods. The names come from the shapes of the cells. The cones - 7 million cells in the central part of the retina, called the macula - are responsible for sharp, detailed vision and color vision. The approximately 100 million rods around them help us see in dim light and provide peripheral vision.
When those focused light rays hit the cells chemical reactions occur that stimulate the optic nerve attached to the back of the retina to produce electrical impulses. Those impulses are then transmitted to the visual cortex, the part of the brain that organizes them. Many parts of the brain cooperate to cause the mind to conclude: 'Ah, a car.' But the visual cortex does the initial heavy lifting.