Frequently Asked Questions (FAQ's)
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A. Contact lenses are small plastic discs, which are curved (on the backside), to the shape of the cornea (the front of the eye). They are curved slightly different on the front to allow them to correct near and farsightedness, astigmatism and presbyopia.
A. “Hard” lenses were the original contact lenses made several decades ago from a plastic called PMMA. For a long time they were the only kind of lens (If you exclude the glass ones experimented with at the beginning of this century) but they are seldom used anymore as they have several drawbacks. They have been replaced by “Rigid” (also known as “Gas Permeable”) lenses. In fact, when people say hard lenses they most likely referring to the gas permeable type. Gas permeable lenses are similar to hard lenses in design and appearance, however, as the name suggests the material they are made of is permeable to gases (Most importantly oxygen and carbon dioxide) whereas PMMA lenses are completely impermeable to gases. “Soft” contact lenses are completely different in that they are slightly larger, flexible, and made of materials that soak up water. In fact, the absorption of water is what allows the soft lenses to transmit oxygen to the cornea. The water gives the lenses flexibility, if you were to allow a soft lens to dry out it becomes quite brittle.
A. The cornea is unusual in that it is transparent, it has to be otherwise light could not enter the eye. The tissues that make up the cornea are able to maintain their transparency partly by not having blood vessels flowing through them. Without blood vessels, the cornea must get its oxygen directly from the air. The oxygen first dissolves in the tears and then diffuses throughout the cornea to keep it healthy. Equally important is carbon dioxide, which is the waste product of a healthy cornea. This diffuses out in the reverse process. Putting any contact lens into the eye will slow or possibly stop these processes. Without enough oxygen the cornea can warp, become less transparent, and become less able to detect pain. Additionally, new blood vessels can grow into the cornea and cause further damage and scarring.
A. As mentioned above, soft lenses soak up water, and it is water which allows the eye to “breath” through the contact lens. Therefore, the more water the lens soaks up, the easier it is for oxygen to pass through the lens to the cornea. The original soft contact lenses are now often referred to as "Low water content” lenses and contain roughly 38% water when fully hydrated. Manufacturers have spent a great deal of time and resources perfecting the use of plastics that are used in contact lenses and as a result the water content of soft contact lenses has risen. Many lenses now contain between 50% and 60% water and some contain over 70%. The amazing thing is that only 30% of a high water content lens are actually plastic. Lenses having over 60% water content are generally considered to be “High water content”, while those lenses between 50% and 65% are called “Mid water content” lenses.
A. There are several disadvantages to high water content lenses. First, because the higher water content lenses contain less plastic, they are more fragile. This means that the lenses are easy to damage or that the manufacturers have to make the lenses thicker thus reducing the effect of the higher water content. Thick lenses transmit less oxygen that thin lenses. Second, higher water content lenses often tend to attract deposits more quickly, making them harder to keep clean. Third, the higher the water content, the easier it is for water to evaporate from the lens and cause the lens to become uncomfortable and less clear.
A. No. They do not need to because the material itself allows oxygen to diffuse through them making water irrelevant.
A. There is no easy answer to this. In terms of oxygen transmission, soft lens materials range from 8 to 35 units of permeability, whereas gas permeable lenses range from 6 to 200. Therefore, if it were just oxygen transmission, then everyone would be wearing gas permeable lenses. The big advantage of gas permeable lenses is that they allow more oxygen to reach the eye in most circumstances. They are small, easy to insert and remove; they give excellent vision, can correct astigmatism and are long lasting. However, they can be difficult to get used to and are best worn daily to maintain the eyes’ tolerance to the lenses. Also, they are more easily dislodged from the eye and so are less useful for sporting activities. Soft lenses are more or less the opposite. They are very stable on the cornea and hence good for sports. They are easy to get used to and can be worn occasionally. However, they do not last long and some types of vision, most notably astigmatism, are harder to correct with soft lenses. If you want tinted or colored contact lenses, then they are presently only available in the soft variety.
A. Astigmatism is usually a natural distortion of the cornea which causes the cornea to become more curved in one direction than in any other direction. Astigmatism is the most common form of refractive error. You can have astigmatism with both near and farsightedness and presbyopia. Occasionally, it can be can be caused by a distortion of the lens inside the eye instead of the cornea, but the effect on focussing is the same. Because the cornea or lens is more curved along one direction it acts as a more powerful lens in that direction causing the image in the back of the eye to be warped.
A. Yes. You may have been told that soft lenses do not correct astigmatism in the past, but this is no longer the case.There is a special type of soft lens called a “Toric” lens that is designed with different curvatures on the front and back to compensate for the astigmatism. They are more difficult to fit and more difficult to manufacture, therefore they tend to be more expensive that standard soft lenses. They are widely available now – you can even get monthly disposable toric lenses.
A. Presbyopia is the process that reduces the eye’s ability to focus on objects close-up as we get older. This is a natural process that is gradual usually starting to affect most people in their 40’s, although you may notice it slightly earlier if you are farsighted. This is a totally natural aging process that is not affected by over wear or under wear of contacts or spectacles. Presbyopia can be present with near or farsightedness as well as astigmatism.
A. Yes. There are several approaches to overcome presbyopia while wearing contact lenses. First, you could wear a pair of reading spectacles over your contact lenses. Alternatively, you could get bifocal contact lenses, which work in a similar way as spectacle bifocals. Then there is a third alternative called monovision. This technique uses one lens for distance vision and one lens for reading in the other eye. The last two alternatives work well for most people but both bifocal and monovision contact lenses have an adaptation period. This adaptation period can last from 1 to 2 days up to a few weeks.
A. “Disposable” contact lenses are those lenses that are designed to be replaced more often than regular lenses. Almost all disposable lenses are of the soft variety. You can replace your lenses yearly, every 6 months, every 3 months, monthly, every 2 weeks, weekly, and now daily. Lenses that are disposed of every 3 and 6 months are called “Frequent Replacement” lenses. The advantage of disposable lenses is that they are thrown away before getting to dirty and are therefore are more healthy for your eyes. Also, because they do not have to last as long, they can be made thinner to improve the ability of oxygen to pass to the cornea through the lens. It is also possible to simplify the cleaning and disinfecting routine as the lenses are replaced more frequently.
A. One of the things that you should not forget is that contact lenses are not a natural thing to have in your eyes. Contact lens solution does three things. First, it cleans and the lenses to make sure that they are clear and comfortable to wear. Cleaning your contact lenses also removes over 90% of the contaminants that can grow on the lenses. Second, lens solution disinfects the lenses and lens case. While the lenses are out of your eyes they are exposed to many contaminants. Your hands, tap water, and the surrounding air to name a few. The disinfectant kills any germs that are on the lens so it reduces the change of getting an eye infection. Third, the lens solution acts as a buffering and wetting solution that makes the lenses more comfortable when inserted. Almost all modern lenses need to be kept wet to prevent them from changing shape and solutions do this also.
A. Yes and no. The dirt that gets on to the lens partly comes from the environment (for example dust) and partly from the eye itself. The tears contain many compounds that stick to the lens and need to be removed to keep them clean. The four main components from tears that get onto the lenses are fats, proteins, mucus, and calcium. Using a daily rub and rinse procedure when removing your lenses will remove almost all of these four components. However, protein is the most difficult to remove and so after a period of several days to a week, a film of protein may form on the lenses. Protein removing tablets are designed to remove this film but remember that they will not remove any other type of deposit. Some peoples’ eyes produce more protein than others do, and so they may have to use protein tablets more often. In addition; some lens materials tend to attract proteins more than others.
A. The best solution to use is the one prescribed for you by your eye care practitioner. They will have assessed how often you replace your lenses, the type of lens materials and whether you are likely to have any allergies to the solutions. Do not change solutions unless you are told to do so by your eye care practitioner. You could end up damaging your lenses, making them less comfortable or possibly giving yourself an eye infection. If you think that you would like to change solutions, talk to your eye care practitioner.
A. Modern contact lenses are made of materials that are designed to be permeable to oxygen, which makes them more permeable to contaminants. Unfortunately, this means that they need to be looked after a lot more carefully. Therefore, the solutions are very thoroughly formulated to ensure that they do not damage your lenses or create possible problems (such as allergic reactions). Do not forget that all contact lens solutions have to be made in conditions that are similar to those used to make drugs to ensure that they are as safe to use as possible. Finally, all lens solutions have to be approved by the FDA. This approval requires many tests on many different types of lenses. This is unfortunately a complicated and expensive procedure. The safety of your eyes is the most important thing.
A. Generally speaking, you should not swim in your contact lenses. This is for two main reasons. First, it is very easy for the lens to be washed out of your eye. Second, the lenses, especially the soft variety will absorb any chemicals or contaminates in the water. The chemicals or contaminants can then stay in or on your lenses for several hours or possibly permanently. This can irritate your eyes making your lenses uncomfortable or possibly giving you an eye infection. You can get prescription swimming goggles or masks that are not too expensive, that are made by opticians. This option is much safer for swimming.
A. You should replace your spectacles at the same time that you update your contact lenses. There are two reasons for this. First, most people should not healthily wear their lenses all day long, every day. Wearing lenses this much can often affect the health of the eye, and it can do this without any symptoms. Secondly, if you do have any trouble with your lenses then you will probably have to stop wearing them and resort back to your spectacles.
A. Both are types of soft lenses that are used to enhance or change the color of the eye. “Tinted” lenses are good at enhancing light colored eyes and can darken light eye with brown or hazel tints. However, if you have dark eyes, then tinted lenses will have no visible affect on their color. Instead you will need to use “Colored” lenses. These lenses have a special colored pattern printed onto the lens that is opaque. In other words, you can not see though the colored part to the natural color of your eye. Because of this, opaque lenses can change even the darkest brown eyes baby blue or green or a wide variety of colors. A lot of new lenses soft and gas permeable now come with a “handling tint”. This is not a tint for cosmetic reasons but to help you see the lens easily.
A. Although the standard “hard” lenses introduced in the 1950’s are still around, technology and materials development have made these lenses virtually obsolete. These lenses are considered specialty lenses used mostly to correct corneal abnormalities. The majority of lenses fitted today are soft and ridged gas permeable (also known as RGP’s). Soft contact lenses, first introduced over 20 years age, are made from a flexible, water absorbent plastic. In fact, these contacts are anywhere from 30% to 80% water. This higher water content increases the oxygen transfer through the lens to the cornea. Soft lenses are designed to be thrown away daily, weekly, every other week, monthly, every 3 months, every 6 months or yearly depending on your eye care practitioner’s instructions. RGP lenses are made of special, firmer plastics that are suited for the passage of oxygen and other gasses. These lenses are very durable and typically last longer than soft lenses. RGP’s offer crisp vision and are often preferred by people with higher degrees of astigmatism. While they may take a little longer to get used to, regular wearers find them comfortable and the visual acuity outstanding.
A. Daily wear lenses are designed to be removed on a daily basis for cleaning, disinfecting and should be taken out before you go to bed or nap. Extended wear lens can be worn continuously for up to 7 days before they are removed for cleaning and disinfecting. Extended wear lenses can also be prescribed to be removed each day for cleaning and slept in occasionally when special circumstances arise. Eye care professionals consider many variables in deciding between daily wear and extended wear lenses for each person’s needs.
A. A growing number of people now wear disposable soft lenses, depending on the lens type, these lenses can be worn a single day or for up to a week. Disposible lenses are usually prescribed in multi-packs, providing several weeks supply at a time. Frequent and planned replacement lenses are lenses that are replaced on a planned schedule, most often every 2 weeks, monthly or quarterly.
A. Contact lenses can correct most vision conditions, including near and far sightedness, astigmatism, and presbyopia. Today’s lenses are lens fitting techniques can help a variety of vision conditions.
A. Advances in materials technology are enabling a significant number of premature babies’ cope with serious eye problems. Premature babies are at a high risk of blindness because their retinas are not completely developed at the time of their birth. While surgery can protect their vision, this procedure often leaves them either very near or far sighted. Contact lenses can provide them the best vision possible and even help their own vision develop better. When contact lenses are prescribed for infants and toddlers, parents and other family members must learn to insert, remove and clean the lenses. Children of all ages can adapt easily to wearing contact lenses.
A. Your eyes and your vision are precious and good contact lens care can help assure a lifetime of healthy eyes. It is important to follow the instructions for daily or weekly lens care prescribed by your eye care professional for your type of lenses. The basic steps include cleaning, rinsing, and disinfecting/storing to keep your soft lenses clean, comfortable and free from bacteria. Weekly enzyme cleaning helps keep your lenses free from deposits of protein naturally produced in your eyes and carried by your tears. RGP lenses utilize a conditioning and cleaning regimen for effective cleaning, storing and comfortable wear. There are also daily disposable lenses available, which do not require as much care as they are designed to be worn for a single day, then thrown away and replaced with a brand new pair. The types of care contacts require—and how long they should be worn is something each eye care professional will prescribe for each patient. Personal wear and care regimens may depend upon the type of contact lens prescribed, the nature of the vision problem being corrected, and the individual’s unique eye chemistry. Regardless of the type of lens you wear, you will find that lens care is now easier and more convenient than ever before.
A. Most first time wearers are delighted with the level of comfort that contact lenses provide. Initial contact lens fittings by professional eye care practitioners can minimize or eliminate any irritation associated with new lenses. After a brief adjustment period, most people report they can no longer feel the contact lenses on their eyes.
A. Athletes of all kinds have discovered the advantages of wearing contact lenses when participating in sports or working out. Contact’s do not steam up from perspiration, they do not smudge and do not get foggy if you from cold to warm temperatures. They provide better depth perception and complete peripheral vision. Today’s close-fitting contacts stay on your eyes, even during vigorous activity.