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Whether you are a new user of eyeglasses or have worn glasses your entire life, you may be considering switching to corrective contact lenses. Contact lenses offer comfort in many different ways, and also have an advantage from an aesthetic point of view. No matter what your motivation is, you may be considering contact lenses as an option if you have been diagnosed with or suffer from any of the following conditions:
- Myopia (nearsightedness)
- Hyperopia (farsightedness)
- Astigmatism (distorted vision)
- Presbyopia (need for bifocals)
If you are considering using corrective contact lenses, you should only do so under the strict supervision of a qualified eye care professional- preferably an ophthalmologist or a contact lens specialist. You should be prepared before going in to your eye care appointment by being aware of the different types of contact lenses that are available in the marketplace. This will help give you a head start in choosing the type of prescription contact lenses that are right for you. The types of contacts that are widely available include the following:
- Rigid Gas-permeable Contact Lenses (RGP's)
- Soft Contact Lenses
- Extended Wear Contact Lenses
- Disposable Contact Lenses
Will my sight worsen if I start wearing prescription contact lenses?
Many people who are considering wearing corrective contact lenses to correct their vision issues are concerned about the possibility of harming their vision further simply by using contact lenses. They may have heard stories or rumors, or may even just have apprehensions about inserting a foreign object into their eye.
First of all, contact lenses should be worn only when prescribed by an ophthalmologist, eye care professional or contact lens specialist. Corrective lenses should only be prescribed after a proper eye exam and diagnosis of one of the following: myopia, hyperopia, astigmatism or presbyopia. Involving a professional from the very beginning will ensure that your eye care is appropriate, adequate and safe.
The Answer is NO!
According to the eye care experts, a corrective contact lens prescription will not make your vision problems worse. Many times when a person tries on contact lenses for the first time, there will be an adjustment period. At first the contact lenses may feel a bit uncomfortable and strange.
If you are used to wearing regular eyeglasses, you may be taken aback by the fact that your peripheral vision is so much better with the contact lenses. In any case, whether you're trying the contact lenses as your first option when diagnosed with vision problems or trying them after using glasses for any period of time, the visual improvement you will experience may be extraordinary. This amazing improvement may make vision without the contacts seem much worse than it actually is, especially the longer your eyes are allowed to grow accustomed to them.
This phenomenon can simply be attributed to the fact that the brain now has a reference point for comparing two images directly: the first one with corrective lenses and the latter one without. Prior to this it had nothing to which a real comparison could be made. Because of this, vision did not seem quite as unclear and blurred, when in fact it really was.
The bottom line is, with proper care and use; contact lenses should not affect your vision in a negative way. Using corrective contact lenses under the care of a contact lens specialist will ensure you are minimizing any chances of causing damage to your eyes.
The concept of lenses made from silicone hydrogel was first proposed over 20 years ago. The potential benefits were clear but the technological challenge was as difficult as needing to combine oil and water to produce an optically clear product. Researcher organizations have to date invested considerable academic and financial resources to achieve the high performance soft lenses of today. They have done this quite simply because they see this material as the way forward and the ultimate standard of the future.
At the time of writing, silicone hydrogel lenses are available in the USA from four manufacturers: "Night & Day" and "O2OPTIX" from CIBA Vision, "Pure Vision" from Bausch & Lomb, and "Acuvue OASYS" and "Advance" from J&J Vision Care.
OXYGEN TRANSPORT
So what’s so special about silicone hydrogel as a lens material? Essentially, the great benefit of this material is it’s ability to transport oxygen to the eye and thus maintain proper eye health. Modern contact lens technology is all to do with oxygen permability, which is measured using the "Dk" index. And for optimal oxygen transmission, this must be as high as possible.
The Dk of traditional, non-silicone based hydrogel lenses is directly related to the amount of water that the material can hold, since oxygen dissolves into the water-component of the material and thus diffuses through the lens. The Dk in fact increases logarithmically with increasing water content. Water itself has a Dk of only 80, thus placing a ceiling on the Dk of convential materials, and the original soft contact lens material, polyHEMA, possesses a Dk of only around 10 (with a water content of about 38%).
However, in silicone hydrogels, the relationship between Dk and water content is the opposite. Here higher water content implies lower Dk. With these lenses Dk increases significantly as the silicone content - not water content - of the lens increases. The Dk values of silicone hydrogel contact lenses are much higher than those of older soft lens materials.
SLEEPING IN CONTACT LENSES
According to market data from CIBA Vision, 84% of soft contact lens wearers occasionally sleep with their lenses in, and one-third admit to doing this regularly. 25% of wearers of one to two-week disposable lenses with low oxygen transmissibility occasionally or routinely sleep in their lenses overnight. And 72% of soft contact lens wearers said they would prefer to be allowed to wear their lenses overnight provided it was safe.
Thus the demand for lenses with the capablities of silicone hydrogels is evidently very high with almost three-quarters of soft lens wearers wanting to be able to sleep in their lenses.
LENS HANDLING
Silicone hydrogel lenses are significantly more rigid than their conventional counterparts, due to the presence of silicone. This increased rigidity does possess some advantages, making the lenses markedly easier to handle and thus the ideal choice for wearers with a less delicate touch. There is a downside to this however in that the rigidity makes the lenses less prone to adopting the shape of the eye so readily, resulting in the possibility for some of reduced comfort.
REDUCED DEPOSITIONS
Historically, the deposition of proteins and lipids has been a problem with contact lenses. The amount of depositions is essentially linked to the duration of wear, the lens material and the tear composition of each individual wearer. With traditional lenses, a frequent replacement schedule greatly reduces the buildup of harmful deposits.
Silicone hydrogel contact lenses have been proven to offer major benefits in the reduction of protein and lysozyme deposition. Indeed, combined with the correct replacement schedule and appropriate care system, problems associated with protein deposition have become almost a thing of the past.
DRY EYES
A problem frequently encountered by wearers of traditional soft contact lenses is one of a feeling of discomfort and "grittiness" in the eyes towards the end of the day. It has been reported that after one week wearing silicone hydrogel lenses, the quantity of regular soft lens wearers in a particular study group who previously suffered significantly from end-of-day dryness, was reduced dramatically to only 13% of the sample.
LIFESTYLE BENEFITS
Silicone hydrogel contact lenses also provide some benefits that conventional lenses don't. Continuous wear contact lenses can be particularly beneficial for use by members of certain professions, such as medical workers, police, the armed forces and firefighters who frequently work unpredictable and long hours.
Furthermore, an increasing numbers of contact lens wearers can now enjoy active outdoor lifestyles, enjoying pursuits such as camping and hiking where it is often difficult to handle and disinfect the lenses with the appropriate level of hygiene.
THE FUTURE FOR CONTACT LENSES
There is much evidence to suggest that, owing to their significant benefits over conventional soft lenses, silicone hydrogel lenses will ultimately, and sooner rather than later, displace other types of contact lens as the prefferred choice for both daily and overnight wear for the majority of contact lens wearers. Silicone hydrogel lenses provide a much improved physical performance, excellent handling properties and greater comfort. They might be considered as the ideal lens for general purpose use that exists today and are likely to become the new everyday standard.