Who can wear contact lenses?
Most people can. Recent advances in contact lenses include astigmatism-correcting lenses, bifocals, daily disposables, and frequent-replacement lenses. Whether you're nearsighted or farsighted, older or younger, you can probably wear some type of contact lens. back to menu
Are contact lenses good for my eyes? Can they cause damage to the cornea?
Contact lenses have proven to be a healthy vision option for millions of people. But only your eyecare professional can determine if they are healthy for you. If you follow all prescribed steps for inserting, removing, and caring for them, contact lenses will continue to be safe and effective. You also need to see your eyecare professional regularly to insure long-term corneal health. back to menu
At what age can contact lens wear begin?
As soon as the need for vision correction is identified, contact lenses are a viable option. In fact, they have frequently been used in premature infants, who sometimes have vision problems. With proper care and lens maintenance, infants, young children, teens, and adults of all ages can wear contacts effectively. If you're a parent, click here for more information. back to menu
Should I wear contact lenses while playing sports?
Sports vision doctors agree that contact lenses are the best vision correction option for athletes. They can enhance visual skills like depth perception, peripheral awareness, and eye-hand/eye-foot coordination. Unlike glasses, contacts offer athletes a competitive advantage because they stay in place under dynamic conditions, provide a wider vision field, and eliminate the risk of glasses-related injuries. Contact lenses also make it easy to wear protective goggles. Click here for more information on contact lenses and sports. back to menu
Is it true that some contact lenses can actually slow or control nearsightedness?
Many contact lens specialists agree that GP contact lenses, which are made of firm plastic, may slow the progression of nearsightedness (myopia), whereas spectacles or soft contact lenses offer no such benefit. Myopia control is one reason why GP contacts are an excellent choice for many school-aged children and teens. Various eyecare practitioners are continuing research in this area. back to menu
If I have astigmatism, can I wear contact lenses?
Yes. Astigmatism is distorted vision caused by an irregularly shaped cornea. Contact lenses that correct astigmatism are called torics, and they come in both soft and GP contact lens materials. GP contacts tend to work better for astigmatism, because they are custom-fit to your eyes' particular shape; also, their firm material keeps its original shape more when you blink. In addition, small amounts of astigmatism may be corrected with a regular, non-toric GP contact lens. back to menu
Aren't soft contact lenses the newest and best technology?
No. When they were first available in 1971, soft contact lenses were a giant leap in technology and comfort over old-style hard contact lenses. But GP contact lenses, first marketed in 1979, are a next-generation advancement. New, recently developed materials and designs make them a state-of-the-art option for contact lens wearers, offering sharper vision, better corneal health, longer lens life, and greater ease of care than most soft contacts. Click here for an in-depth comparison of GPs and soft lenses. back to menu
Are contacts hard to take care of?
It differs from lens to lens. GP contacts, which last for years, need daily cleaning and disinfecting but generally no enzyming, since their slick surface resists deposit buildup. Daily disposable lenses are worn once, then discarded, with no maintenance required. Weekly soft disposables are cleaned at the end of the day, then soaked in disinfecting solution until they're worn again. Since they're discarded before deposit buildups occur, they don't need to be soaked in an enzyme solution. Other soft lenses usually require daily cleaning/disinfection and weekly enzyming. back to menu
How can I get contact lenses that change the appearance or color of my eyes?
Soft contact lenses are available that will change the color of your eyes, even if you don't require vision correction. Costume lenses for Halloween or theatrical purposes are also available. Both are still a prescribed medical device that must be fitted and followed up by your eyecare professional. And remember, even though such lenses might provoke curiosity by your friends and family members, never share them with anyone. Sharing lenses can lead to dangerous health problems. back to menu
Who should I see for contacts -- an optometrist or an ophthalmologist?
It is your choice. Optometrists (Doctors of Optometry, or O.D.s) perform eye examinations, treat eye disease, prescribe vision correction, fit contact lenses, and dispense eyeglasses. Ophthalmologists are medical doctors (M.D.s) who specialize in eyes. Many concentrate on eye surgery and treatment of disease, but some specialize in contact lenses. Also, in some states specially trained opticians or contact lens technicians are licensed to fit contact lenses. Since they must fit the lenses from an optometrist's or ophthalmologist's prescription, they often work with them in the same office. back to menu
How much do contact lenses cost?
The cost of contact lenses can vary greatly. If you have a difficult prescription or need correction for problems like astigmatism, your lenses will be more expensive. If you have no special requirements, your options will range from daily disposables (fairly high cost) to GP contacts, which are thought by many to provide the greatest value. GP contacts, though initially more expensive, can last for years and are inexpensive to care for. Consumer Reports called GP contact lenses a better buy "because they're more durable and cheaper to maintain." Fortunately, GP contacts can also accommodate any prescription, no matter how difficult, because they are custom-made for each individual wearer. back to menu
Can I sleep in contact lenses?
Ask your doctor. It depends on the type of lens you're wearing, the composition of your tear film, your general eye health, and other factors. GP contact lenses and certain soft lenses can be slept in, but never wear them while sleeping unless your eyecare practitioner says you can. back to menu
I've never worn contact lenses, and the thought of putting something in my eye is a little scary.
This is a typical concern with first-time wearers, but your eyecare professional will be able to help. Here are some of the most common worries:
"I can't get my eye open wide enough." Yes you can. Grasp the upper eyelashes between your thumb and index finger and gently pull the eyelids apart.
"My eyes are too small." They aren't. Hold the top lid up and rest the edge of the lens inside the lower lid with the lens slanting out. If you look down, the lens usually moves right onto the eye.
"What if I put the lens in the wrong place?" You can't. The lens won't fit right unless it's centered, and it has a natural tendency to move to the center of your eye. Your eyecare professional can show you how to move it into position if you do get the lens off the cornea.
"What if the lens slides to the back of my eyeball?" Don't worry, this is completely impossible.
"The lens won't stick in place." Usually it's because the lens is attracted to the wettest surface, and your finger is wetter than your eye. Dry your finger, and let your lens air-dry for a few seconds before insertion.
"I'm afraid I'll put my lens on inside-out." The good thing about GP contact lenses is that they can't flip inside-out. But if it's a soft lens, look at it closely. If the edge is flared out, it's probably inside-out. Some soft lenses have little marks to help you know if they're inside out.
"How do I get the lens out again? Isn't it stuck to my eye?" No. If you're wearing a GP contact lens, just pull your eyelid taut to the side and blink. It pops right out. For a soft lens, use a few drops of rewetting or solution to keep the lens wet. Look up, touch the lens, and let it slide down and over to the outside corner of the eye. The lens will bunch up, so it's easy to fold out.
"Will I give myself an eye problem by touching the lens?" No. Just make sure to wash your hands first. back to menu
Contact lens
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A pair of contact lenses when not inserted in the eye. They are positioned with the concave side facing upward.A contact lens (also known simply as a "contact") is a corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye.
Contact lenses usually serve the same corrective purpose as conventional glasses, but are lightweight and virtually invisible — many commercial lenses are tinted a faint blue to make them more visible when immersed in cleaning and storage solutions. Cosmetic lenses are deliberately coloured for altering the appearance of the eye.
It has been estimated that about 125 million people use contact lenses worldwide (2%)[1], including 28 to 38 million in the United States[2][1] and 13 million in Japan [3]. The types of lenses used and prescribed vary markedly between countries, with rigid lenses accounting for over 20% of currently-prescribed lenses in Japan, Netherlands and Germany but less than 5% in Scandinavia[1].
People choose to wear contact lenses for various reasons[4]. Many consider their appearance to be more attractive with contact lenses than with glasses. Contact lenses are less affected by wet weather, do not steam up, and provide a wider field of vision. They are more suitable for a number of sporting activities[5]. Additionally, ophthalmological conditions such as keratoconus and aniseikonia may not be accurately correctable with glasses.
Contents [hide]
1 History
2 Types of contact lenses
2.1 By function
2.2 By constructional material
2.3 By wear time
2.4 By disposability
2.5 By shape
2.6 By number of focal points
2.7 Implantation
3 Manufacturing of contact lenses
4 Prescribing contact lenses
5 Complications
6 Contact lens care: cleaning and disinfection products
7 References and sources
8 See also
9 External links
[edit]
History
In 1887, Adolf Fick was apparently the first to successfully fit contact lenses, which were made from brown glassLeonardo da Vinci is frequently credited with introducing the general principle of contact lenses in his 1508 Codex of the eye, Manual D, where he described a method of directly altering corneal power by submerging the eye in a bowl of water. Leonardo, however, did not suggest his idea be used for correcting vision--he was more interested in learning about the mechanisms of accommodation of the eye.[6]
René Descartes proposed another idea in 1636, in which a glass tube filled with liquid is placed in direct contact with the cornea. The protruding end was to be composed of clear glass, shaped to correct vision; however the idea was unworkable, since it would make blinking impossible.
In 1801, while conducting experiments concerning the mechanisms of accommodation, scientist Thomas Young constructed a liquid-filled "eyecup" which could be considered a predecessor to the contact lens. On the eyecup's base, Young fitted a microscope eyepiece. However, like da Vinci's, Young's device was not intended to correct refraction errors.
Sir John Herschel, in a footnote of the 1845 edition of the Encyclopedia Metropolitana, posed two ideas for the visual correction: the first "a spherical capsule of glass filled with animal jelly", and "a mould of the cornea" which could be impressed on "some sort of transparent medium". Though Herschel reportedly never tested these ideas, they were both later advanced by several independent inventors, seemingly unaware of Herschel's suggestion.
It was not until 1887 that the German physiologist Adolf Eugen Fick constructed and fitted the first successful contact lens. While working in Zürich, he described fabricating afocal scleral contact shells, which rested on the less sensitive rim of tissue around the cornea, and experimentally fitting them: initially on rabbits, then on himself, and lastly on a small group of volunteers. These lenses were made from heavy brown glass and were 18-21mm in diameter. Fick filled the empty space between cornea/callosity and glass with a grape sugar solution. He published his work, "Contactbrille", in the journal Archiv für Augenheilkunde in March 1888.
Fick's lens was large, unwieldy, and could only be worn for a few hours at a time. August Müller in Kiel, Germany, corrected his own severe myopia with a more convenient glass-blown scleral contact lens of his own manufacture in 1888.
Glass-blown scleral lenses remained the only form of contact lens until the 1930s when polymethyl methacrylate (PMMA or Perspex/Plexiglas) was developed, allowing plastic scleral lenses to be manufactured for the first time. In 1936 an optometrist, William Feinbloom introduced plastic lenses, making them lighter and more convenient.[7] These lenses were a combination, however, of both plastic and glass.
In the 1950s, the first 'corneal' lenses were developed--these were much smaller than the original scleral lenses, as they sat only on the cornea rather than across all of the visible ocular surface. PMMA corneal lenses became the first contact lenses to have mass appeal through the 1960s, as lens designs became more sophisticated with improving manufacturing (lathe) technology.
One important disadvantage of PMMA lenses is that no oxygen is transmitted through the lens to the cornea, which can cause a number of adverse clinical events. By the end of the 1970s, and through the 1980s and 1990s, a range of oxygen-permeable but rigid materials were developed to overcome this problem. Collectively, these polymers are referred to as 'rigid gas permeable' or 'RGP' materials or lenses. Although all the above lens types--sclerals, PMMA lenses and RGPs--could be correctly referred to as being 'hard' or 'rigid', the term 'hard' is now used to refer to the original PMMA lenses which are still occasionally fitted and worn, whereas 'rigid' is a generic term which can be used for all these lens types. That is, 'hard' lenses (PMMA lenses) are a sub-set of 'rigid' lenses. Occasionally, the term 'gas permeable' is used to describe RGP lenses, but this is potentially misleading, as soft lenses are also 'gas permeable' in that they allow oxygen to move through the lens to the ocular surface.
The principal breakthrough in soft lenses was made by the Czech chemist Otto Wichterle who published his work "Hydrophilic gels for biological use" in the journal Nature in 1959[8]. This led to the launch of the first soft (hydrogel) lenses in some countries in the 1960s and the first approval of the 'Soflens' material by the United States Food and Drug Administration (FDA) in 1971. These lenses were soon prescribed more often than rigid lenses, mainly due to the immediate comfort of soft lenses; by comparison, rigid lenses require a period of adaptation before full comfort is achieved. The polymers from which soft lenses are manufactured improved over the next 25 years, primarily in terms of increasing the oxygen permeability by varying the ingredients making up the polymers.
In 1999, an important development was the launch of the first 'silicone hydrogels' onto the market. These new materials encapsulated the benefits of silicone—which has extremely high oxygen permeability—with the comfort and clinical performance of the conventional hydrogels which had been used for the previous 30 years. These lenses were initially advocated primarily for extended (overnight) wear although more recently, daily (no overnight) wear silicone hydrogels have been launched.
[edit]
Types of contact lenses
Contact lenses are classified in many different manners.[9] [10]
[edit]
By function
Corrective contact lenses - A corrective contact lens is a lens designed to improve vision. In many people, there is a mismatch between the refractive power of the eye and the length of the eye, leading to a refraction error. A contact lens neutralizes this mismatch and allows for correct focusing of light onto the retina. Conditions correctable with contact lenses include near (or short) sightedness (myopia), far (or long) sightedness (hypermetropia), astigmatism and presbyopia. Recently there has been renewed interest in orthokeratology, the correction of myopia by deliberate overnight flattening of the cornea, leaving the eye without contact lens or eyeglasses correction during the day.
For those with certain color deficiencies, a red-tinted "X-Chrom" contact lens may be used. Although the lens does not restore normal color vision, it allows some colorblind individuals to distinguish colors better[11][12]. Other tinted lenses have been used with limited success[13].
A person seen wearing two different styles of cosmetic contact lensesCosmetic contact lenses - A cosmetic contact lens is designed to change the appearance of the eye. These lenses may also correct the vision, but some blurring or obstruction of vision may occur as a result of the color or design. In the United States, the FDA frequently calls non-corrective cosmetic contact lenses decorative contact lenses[14][15][16][17].
Theatrical contact lenses are a type of cosmetic contact lens that are used primarily in the entertainment industry to make the eye appear unusual or unnatural in appearance[18]. These lenses have been used by Wes Borland, Marilyn Manson, Twiztid, World Wrestling Entertainment (WWE) wrestlers Kane, Rey Mysterio and Viscera, and Ray Park as Darth Maul in Star Wars Episode I: The Phantom Menace. Scleral lenses cover the white part of the eye (i.e. sclera) and are used in many theatrical lenses.
Similar lenses have more direct medical applications. For example, some lenses can give the iris an enlarged appearance, or mask defects such as absence (aniridia) or damage (dyscoria) to the iris.
Although many brands of contact lenses are lightly tinted to make them easier to handle, cosmetic lenses worn to change the color of the eye are far less common, accounting for only 3% of contact lens fits in 2004[19].
Therapeutic contact lenses - Soft lenses are often used in the treatment and management of non-refractive disorders of the eye. A bandage contact lens protects an injured or diseased cornea from the constant rubbing of blinking eyelids thereby allowing it to heal[20]. They are used in the treatment of conditions including bullous keratopathy, dry eyes, corneal ulcers and erosion, keratitis, corneal edema, descemetocele, corneal ectasis, Mooren's ulcer, anterior corneal dystrophy, and neurotrophic keratoconjunctivitis[21]. Contact lenses to deliver drugs to the eye have also been developed[22].
[edit]
By constructional material
Contact lenses, once inserted in the eye, become almost invisible (except cosmetic contact lenses).The first contact lenses were made of glass, which caused eye irritation, and so were not able to be worn for extended periods of time. But when Dr. William Feinbloom introduced lenses made from polymethyl methacrylate (PMMA or Perspex/Plexiglas), contacts become much more convenient. These PMMA lenses are commonly referred to as "hard" lenses (this term is not used for other types of contacts).
However, PMMA lenses have their own side effects: no oxygen is transmitted through the lens to the cornea, which can cause a number of adverse clinical events. In the late 1970s, and through the 1980s and 1990s, improved rigid materials — which were also oxygen-permeable — were developed. Collectively, these polymers are referred to as 'rigid gas permeable' or 'RGP' materials or lenses.
Rigid lenses offer a number of unique properties. In effect, the lens is able to replace the natural shape of the cornea with a new refracting surface. This means that a regular (spherical) rigid contact lens can provide good level of vision in people who have astigmatism or distorted corneal shapes as with keratoconus.
Whilst rigid lenses have been around for about 120 years, soft lenses are a much more recent development. The principal breakthrough in soft lenses made by Otto Wichterle led to the launch of the first soft (hydrogel) lenses in some countries in the 1960s and the approval of the 'Soflens' material (polymacon) by the United States FDA in 1971. Soft lenses are immediately comfortable, while rigid lenses require a period of adaptation before full comfort is achieved. The polymers from which soft lenses are manufactured improved over the next 25 years, primarily in terms of increasing the oxygen permeability by varying the ingredients making up the polymers.
A small number of hybrid rigid/soft lenses exist. An alternative technique is piggybacking of contact lenses, a smaller, rigid lens being mounted atop a larger, soft lens. This is done for a variety of clinical situations where a single lens will not provide the optical power, fitting characteristics, or comfort required.
In 1999, 'silicone hydrogels' became available. Silicone hydrogels have both the extremely high oxygen permeability of silicone and the comfort and clinical performance of the conventional hydrogels. These lenses were initially advocated primarily for extended (overnight) wear, although more recently daily (no overnight) wear silicone hydrogels have been launched.
While it provides the oxygen permeability, the silicone also makes the lens surface highly hydrophobic and less "wettable." This frequently results in discomfort and dryness during lens wear. In order to compensate for the hydrophobicity, hydrogels are added (hence the name "silicone hydrogels") to make the lenses more hydrophilic. However the lens surface may still remain hydrophobic. Hence some of the lenses undergo surface modification processes which cover the hydrophobic sites of silicone. Some other lens types incorporate internal rewetting agents to make the lens surface hydrophilic.
[edit]
By wear time
A daily wear contact lens is designed to be removed prior to sleeping. An extended wear (EW) contact lens is designed for continuous overnight wear, typically for 6 or more consecutive nights. Newer materials, such as silicone hydrogels, allow for even longer wear periods of up to 30 consecutive nights; these longer-wear lenses are often referred to as continuous wear (CW). Generally, extended wear lenses are discarded after the specified length of time. These are increasing in popularity, due to their obvious convenience. Extended- and continuous-wear contact lenses can be worn for such long periods of time because of their high oxygen permeability (typically 5-6 times greater than conventional soft lenses), which allows the eye to remain remarkably healthy.
Extended lens wearers may have an increased risk for corneal infections and corneal ulcers, primarily due to poor care and cleaning of the lenses, tear film instability, and bacterial stagnation. Corneal neovascularization is also a common complication of extended lens wear, however the most common complication of extended lens use is conjunctivitis usually allergic or giant papillary conjunctivitis (GPC) associated with a poorly fitting contact lens.
[edit]
By disposability
The various soft contact lenses available are often categorized by their replacement schedule. The shortest replacement schedule is single use lenses, which are disposed of each night. These may be best for patients with ocular allergies or other conditions because it limits deposits of antigens and protein. Single use lenses are also useful for people who use contacts infrequently. More commonly, contact lenses are prescribed to be disposed of on a two-week or monthly basis. Quarterly or annual lenses, which used to be very common, have lost favor because a more frequent disposal schedule allows for thinner lenses and limits deposits. Rigid gas permeable lenses are very durable and may last for several years without the need for replacement
[edit]
By shape
A spherical contact lens is one in which both the inner and outer optical surfaces are portions of a sphere. A toric lens is one in which either or both of the optical surfaces have the effect of a cylindrical lens, usually in combination with the effect of a spherical lens. Myopic (nearsighted) and hypermetropic (farsighted) people who also have astigmatism and who have been told they are not suitable for regular contact lenses may be able to use toric lenses. If one eye has astigmatism and the other doesn't, the patient may be told to use a spherical lens in one eye and a toric lens in the other. Toric lenses are made from the same materials as regular contact lenses but have a couple of extra characteristics:
They correct for both spherical and cylindrical aberration.
They have a specific top and bottom, as they are not symmetrical around their centre and must not be rotated. Lenses must be designed to maintain their orientation regardless of eye movement. Often lenses are weighted more at the bottom and are marked by tiny striations so the wearer can insert them in the correct orientation, or they are designed so that the correct orientation is restored when the user blinks. Some do both.
[edit]
By number of focal points
Similarly to eyeglasses, contact lenses can have one (single vision) or more (multifocal) focal points.
For correction of presbyopia or accommodative insufficiency multifocal contact lenses are almost always used; however, single vision lenses may also be used in a process known as monovision[23]: single vision lenses are used to correct one eye's far vision and the other eye's near vision. Alternatively, a person may wear single vision contact lenses to improve distance vision and reading glasses to improve near vision.
Multifocal contact lenses are more complex to manufacture and require more skill to fit. All soft bifocal contact lenses are considered "simultaneous vision" because both far and near vision are corrected simultaneously, regardless of the position of the eye. Commonly these are designed with distance correction in the center of the lens and near correction in the periphery, or viceversa. Rigid gas permeable contact lenses most commonly have a small lens on the bottom for the near correction: when the eyes are lowered to read, this lens comes into the optical path.
[edit]
Implantation
Intraocular contact lenses, also known as an implantable contact lenses, are special small corrective lenses surgically implanted in the eye's posterior chamber behind the iris and in front of the lens to correct higher amounts of myopia and hyperopia.
[edit]
Manufacturing of contact lenses
Most contact lenses are mass produced.
Spin-cast lenses - A spin cast lens is a soft contact lens manufactured by whirling liquid plastic in a revolving mold at high speed[24].
Lathe cut - A lathe cut contact lens is cut and ground on a lathe [24].
Molded
Hybrids
Although many companies make contact lenses, there are four major manufacturers: Vistakon/Johnson & Johnson, CIBA Vision, Bausch & Lomb, and CooperVision[25].
[edit]
Prescribing contact lenses
The prescribing of contact lenses is usually restricted to appropriately qualified eye care practitioners. In countries such as the United States (where all contact lenses are deemed to be medical devices by the Food and Drug Administration), the United Kingdom and Australia, optometrists are usually responsible. In France and eastern European countries, ophthalmologists play the major role. In other parts of the world, opticians usually prescribe contact lenses. Prescriptions for contact lenses and glasses may be similar, but are not interchangeable.
The practitioner or contact lens fitter typically determines an individual's suitability for contact lenses during an eye examination. Corneal health is verified; ocular allergies or dry eyes may affect a person's ability to successfully wear contact lenses.
The parameters specified in a contact lenses prescription may include:
Material (eg. Oxygen Permeability/Transmissibility (Dk/L, Dk/t), water content, modulus)
Base curve radius (BC, BCR)
Diameter (D, OAD)
Power in dioptres - Spherical, Cylindrical and/or reading addition)
Cylinder axis
Center thickness (CT)
Brand
[edit]
Complications
Complications due to contact lens wear are relatively common, affecting roughly 5% of contact lens wearers each year [26]. Excessive wear of contact lenses, particularly overnight wear, is associated with the most serious safety concerns[2]. Problems associated with contact lens wear may affect the eyelid, the conjunctiva, the various layers of the cornea, and even the tear film that covers the outer surface of the eye[26].
Eyelid:
Ptosis
Conjunctiva:
Contact dermatitis
Giant papillary conjunctivitis
Superior limbic keratoconjunctivitis
Cornea:
Epithelium
Corneal abrasion
Corneal erosion
Corneal ulcer
Hypoxia
Stroma
Infection and keratitis
Bacteria
Protozoa: Acanthamoeba
Fungal: Fusarium[27]
Contact lens acute red eye (CLARE)
Keratoconus
Endothelium
[edit]
Contact lens care: cleaning and disinfection products
While daily disposable lenses require no cleaning, other types require regular cleaning and disinfecting in order to retain clear vision and prevent discomfort and infections by various microorganisms including bacteria, fungi, and Acanthamoeba, that form a biofilm on the lens surface. There are a number of products that can be used to perform these tasks:
Multipurpose solution - The most popular cleaning solution for contact lenses. Used for rinsing, disinfecting, cleaning and storing the lenses. Using this product eliminates the need for multiple solutions.
Saline solution - Used for rinsing the lens after cleaning and preparing it for insertion. Saline solutions do not disinfect the lenses.
Daily cleaner - Used to clean lenses on a daily basis. A few drops of cleaner are applied to the lens while it rests in the palm of the hand, then the lens is rubbed for about 20 seconds with a fingertip (check the cleaner's directions) on each side. Long fingernails can damage the lens, so care should be taken.
Hydrogen peroxide solution - Used for disinfecting the lenses, and available as 'two-step' or 'one-step' systems. If using a 'two-step' product, one must ensure that the lens taken out of the hydrogen peroxide is neutralized before it is worn, or else wear will be extremely painful. Saline must not be used to rinse away the peroxide. Some peroxide solutions, such as CIBA Vision's Clear Care, come with a special storage case that contains a catalyzing disk. If soaked in the solution with the disk for at least six hours, the hydrogen peroxide decomposes and the remaining solution is a saline that will not harm the eye. People with extremely sensitive, irritable eyes often use these types of cleaning solutions.
Enzymatic cleaner - Used for cleaning protein deposits off lenses, usually weekly, if the daily cleaner is not sufficient. Typically, this cleaner is in tablet form. Protein deposits make use of contact lenses uncomfortable, and may lead to various eye problems.
Some products must only be used with certain types of contact lenses: it is important to check the product label to make sure that it can be used for a given type of lens. It is also important to follow the product's directions carefully to reduce risk of eye infection or eye irritation.
It is important to ensure that the product does not become contaminated with microorganisms: the tips of the containers for these solutions should never touch any surface, and the container should be kept closed when not in use. To counteract minor contamination of the product and kill microorganisms on the contact lens, some products may contain preservatives such as thimerosal, benzalkonium chloride, benzyl alcohol, and other compounds. In 1989, thimerosal was responsible for about 10% of problems related to contact lenses[28]: because of this, many products no longer contain thimerosal. Preservative-free products usually have shorter shelf life. For example, non-aerosol preservative-free saline solutions can typically be used for only two weeks once opened.
Before touching the contact lens or one's eyes, it is important to thoroughly wash & rinse hands with a soap that does not contain moisturizers or allergens such as fragrances.