A pair of contact lenses, positioned with the concave side facing upward.

One-day disposable blue color contact lens

A contact lens (also known simply as a "contact") is a corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye. Modern soft contact lenses were invented by the Czech chemist Otto Wichterle, who also invented the first gel used for their production. Image File history File linksMetadata Download high resolution version (2560x1920, 1331 KB) contact lenses Confortissimo - own picture File links The following pages link to this file: Contact lens Metadata This file contains additional information, probably added from the digital camera or scanner used to create or digitize it. ... Image File history File linksMetadata Download high resolution version (2560x1920, 1331 KB) contact lenses Confortissimo - own picture File links The following pages link to this file: Contact lens Metadata This file contains additional information, probably added from the digital camera or scanner used to create or digitize it. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 572 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 572 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... A bifocal corrective eyeglasses lens A corrective lens is a lens worn in front of the eye, mainly used to treat myopia, hyperopia, astigmatism, and presbyopia. ... Make-up redirects here. ... This article is about the optical device. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... For other uses, see Eye (disambiguation). ... A chemist pours from a round-bottom flask. ... Prof. ... In optical filters and theatrical lighting a color gel is a transparent or translucent colored panel used to change the color of transmitted light. ...

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. Some cosmetic lenses are deliberately colored to alter the appearance of the eye. A pair of modern glasses Glasses, also called eyeglasses or spectacles are frames, bearing lenses worn in front of the eyes normally for vision correction, eye protection, or for protection from UV rays. ...

It has been estimated that 125 million people use contact lenses worldwide (2%),^[1] including 28 to 38 million in the United States^[1][2]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] For other uses, see Scandinavia (disambiguation). ...

People choose to wear contact lenses for various reasons.^[4] Many consider their appearance to be more attractive with contact lenses than with glasses^{[citation needed]}. 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 corrected with glasses. This article is about the branch of medicine. ... Keratoconus (from Greek: kerato- horn, cornea; and konos cone), is a degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve. ... The following text is a summary of Optical Diagnostics aniseikonia information webpage. ...

History

In 1887, Adolf Fick was apparently the first to successfully fit contact lenses, which were made from brown glass

Leonardo 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] Image File history File links Adolf_Fick. ... Image File history File links Adolf_Fick. ... “Da Vinci” redirects here. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ...

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 impracticable, since it would make blinking impossible. René Descartes (French IPA:  Latin:Renatus Cartesius) (March 31, 1596 – February 11, 1650), also known as Renatus Cartesius (latinized form), was a highly influential French philosopher, mathematician, scientist, and writer. ...

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 Leonardo's, Young's device was not intended to correct refraction errors. Thomas Young, English scientist Thomas Young (June 13, 1773-May 10, 1829) was an English polymath, contributing to the scientific understanding of vision, light, solid mechanics, energy, physiology, and Egyptology. ...

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".^[7] Though Herschel reportedly never tested these ideas, they were both later advanced by several independent inventors such as Hungarian Dr. Dallos (1929), who perfected a method of making molds from living eyes. This enabled the manufacture of lenses that, for the first time, conformed to the actual shape of the eye. John Herschel Sir John Frederick William Herschel (7 March 1792 – 11 May 1871) was an English mathematician and astronomer. ... The Encyclopaedia Metropolitana was published in London, 1845, quarto, 30 vols. ... For the art collective, see Gelitin. ...

It was not until 1887 that a German glassblower, F.E. Muller, produced the first eye covering to be seen through and tolerated.^[8] In the next year, 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 dextrose solution. He published his work, "Contactbrille", in the journal Archiv für Augenheilkunde in March 1888. Portrait of Fick Adolf Eugen Fick (born 3 September, 1829, in Kassel, Germany; died 21 August, 1901, in Blankenberge, Flanders) was a German physiologist usually credited with the invention of contact lenses. ... For other uses of Zurich, see Zurich (disambiguation). ... A scleral lens is a large type of contact lens that rests on the sclera and creates a tear-filled vault over the cornea. ... Nature, Science and PNAS In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. ...

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.^[9] August Müller (1864 – 1949), born in Mönchengladbach, was a medical student at the University of Kiel, Germany, and a pioneer in the manufacture of contact lenses. ... , For the city in the United States, see Kiel, Wisconsin. ...

Also in 1887, Louis J. Girard invented a similar scleral form of contact lens.^[10] Louis J. Girard developed the first form of contact lens in 1887. ...

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, optometrist William Feinbloom introduced plastic lenses, making them lighter and more convenient.^[11] These lenses were a combination of glass and plastic. Structure of methyl methacrylate, the monomer that makes up PMMA Polymethyl methacrylate (PMMA) or poly(methyl 2-methylpropenoate) is the synthetic polymer of methyl methacrylate. ... Dr. William Feinbloom (born in Brooklyn in 1904, died in 1985) was a pioneer in the field of vision rehabilitation. ...

In 1949, the first "corneal" lenses were developed.^{[12][13][14][15]} 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, and could be worn up to sixteen hours per day. 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. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ...

One important disadvantage of PMMA lenses is that no oxygen is transmitted through the lens to the conjunctiva and cornea, which can cause a number of adverse clinical effects. 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. Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ... A polymer is a long, repeating chain of atoms, formed through the linkage of many molecules called monomers. ...

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.^[16] 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. Prof. ... FDA redirects here. ... Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ...

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. Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ...

Types of contact lenses

Contact lenses are classified in many different manners.^{[17] [18]}

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. Contact wearers must usually take their contacts out every night or every few days, depending on the brand and style of the contact. 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. Refraction error is an error in the focussing of light by the human eye. ... Human eye cross-sectional view. ... For other uses, see Myopia (disambiguation). ... Hyperopia (or more rarely, hypermetropia), also known as farsightedness or longsightedness, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short), causing inability to focus on near objects, and in extreme cases causing a sufferer to be unable to focus on... Astigmatism is an affliction of the eye, where vision is blurred by an irregularly shaped cornea. ... Presbyopia (Greek word presbyteros (πρεσβύτερος), meaning elder) is the eyes diminished ability to focus that occurs with aging. ... Orthokeratology (Ortho-K) is the use of rigid gas-permeable contact lenses, normally worn only at night, to improve vision through the reshaping of the cornea. ... For other uses, see Myopia (disambiguation). ...

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.^[19][20] Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect or emit. ...

ChromaGen lenses have been used and these have been shown to have some limitations with vision at night although otherwise producing significant improvements in colour vision.^[21] An earlier study showed very significant improvements in colour vision and patient satisfaction^[22]

Later work that used these ChromaGen lenses with dyslexics in a randomised, double-blind, placebo controlled trial showed highly significant improvements in reading ability over reading without the lenses ^[23] This system has been granted FDA approval in the United States, which is reassuring to patients.

Cosmetic 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.^{[24][25][26][27]} The United States Food and Drug Administration is the government agency responsible for regulating food, dietary supplements, drugs, cosmetics, medical devices, biologics and blood products in the United States. ...

Theatrical contact lenses are a type of cosmetic contact lens that are used primarily in the entertainment industry to make the eye appear pleasing, unusual or unnatural in appearance^[28], most often in horror and zombie movies, where lenses can make one's eyes appear demonic, cloudy and lifeless, or even to make the pupils of the wearer appear dilated to simulate the natural appearance of the pupils under the influence of various illicit drugs. The entertainment industry consists of a large number of sub-industries devoted to entertainment. ... “Horror Movie” redirects here. ... This article is about the living dead. ...

Scleral lenses cover the white part of the eye (i.e. sclera) and are used in many theatrical lenses..^[29] Due to their size, these lenses are difficult to insert and do not move very well within the eye. They may also hamper the vision as the lens has a small area for the user to see through. As a result they generally cannot be worn for more than 3 hours as they can cause temporary vision disturbances.^[30] A scleral lens is a large type of contact lens that rests on the sclera and creates a tear-filled vault over the cornea. ... Schematic diagram of the human eye. ...

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. In anatomy, the iris (plural irises or irides) is the most visible part of the eye of vertebrates, including humans. ... Aniridia is a rare congenital condition characterized by the underdevelopment of the eyes 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.^[31]

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.^[32] 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.^[33] Contact lenses that deliver drugs to the eye have also been developed.^[34] Keratoconjunctivitis sicca (KCS), also called keratitis sicca,[1] sicca syndrome,[1] xerophthalmia,[1] dry eye syndrome (DES),[1] or simply dry eyes,[1] is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in humans and some animals[2]. Keratoconjunctivitis sicca is Latin and... For corneal abrasions in dogs and cats, see corneal ulcer. ... Recurrent corneal erosion is a disorder of the eyes characterized by the failure of the corneas outermost layer of epithelial cells to attach to the underlying basement membrane (Bowmans membrane). ... This page is about the condition called edema. ... A corneal ulcer is an inflammatory condition of the cornea involving loss of its outer layer. ...

By constructional material

Contact lenses, other than the cosmetic variety, become almost invisible once inserted in the eye

The first contact lenses were made of glass, which caused eye irritation, and were not wearable for extended periods of time. But when William Feinbloom introduced lenses made from polymethyl methacrylate (PMMA or Perspex/Plexiglas), contacts became much more convenient. These PMMA lenses are commonly referred to as "hard" lenses (this term is not used for other types of contacts). Image File history File links Metadata Size of this preview: 800 × 596 pixelsFull resolution (1562 × 1163 pixel, file size: 152 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Metadata Size of this preview: 800 × 596 pixelsFull resolution (1562 × 1163 pixel, file size: 152 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... This article is about the material. ... Dr. William Feinbloom (born in Brooklyn in 1904, died in 1985) was a pioneer in the field of vision rehabilitation. ... Structure of methyl methacrylate, the monomer that makes up PMMA Polymethyl methacrylate (PMMA) or poly(methyl 2-methylpropenoate) is the synthetic polymer of methyl methacrylate. ... Structure of methyl methacrylate, the monomer that makes up PMMA Polymethyl methacrylate (PMMA) or poly(methyl 2-methylpropenoate) is the synthetic polymer of methyl methacrylate. ...

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. One advantage of hard lenses is that, due to their non-porous nature, they do not absorb chemicals or fumes. The absorption of such compounds by other types of contacts can be a problem for those who are routinely exposed to painting or other chemical processes. This article is about the chemical element and its most stable form, or dioxygen. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ... A polymer is a long, repeating chain of atoms, formed through the linkage of many molecules called monomers. ...

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. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... Keratoconus (from Greek: kerato- horn, cornea; and konos cone), is a degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve. ...

While 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. Prof. ... Hydrogel is a network of polymer chains that are water-insoluble, sometimes found as a colloidal gel in which water is the dispersion medium. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ...

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. Optical power or dioptric power or refractive power is the degree to which a lens or mirror converges or diverges light. ...

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. Not to be confused with the element silicon. ... Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ... Not to be confused with the element silicon. ...

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. Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ...

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 healthy. Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ...

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 has historically also been a common complication of extended lens wear, though this does not appear to be a problem with silicone hydrogel extended wear. The most common complication of extended lens use is conjunctivitis, usually allergic or giant papillary conjunctivitis (GPC), sometimes associated with a poorly fitting contact lens. A corneal ulcer is an inflammatory condition of the cornea involving loss of its outer layer. ... Corneal neovascularization is the excessive ingrowth of blood vessels from the limbal vascular plexus into the cornea. ... Allergy is an abnormal reaction to a substance foreign to the body that is acquired, predictable and rapid. ... Conjunctivitis (IPA: ), commonly called Pink Eye and Red Eye in the UK, and Madras Eye in India is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), most commonly due to an allergic reaction or an infection (usually bacterial, or viral). ...

By frequency of replacement

The various soft contact lenses available are often categorized by their replacement schedule. The shortest replacement schedule is single use (daily disposable) 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, or for purposes (e.g. swimming or other sporting activities) where losing a lens is likely. 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. PMMA hard lenses were very durable, and were commonly worn for 5 to 10 years. This article needs cleanup. ... An antigen is any molecule that is recognized by antibodies. ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ...

By design

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 does not, 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 few extra characteristics: Normal vision for a achromatopsic colour-blind person. ... Hyperopia (or more rarely, hypermetropia), also known as farsightedness or longsightedness, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short), causing inability to focus on near objects, and in extreme cases causing a sufferer to be unable to focus on... Astigmatism is an affliction of the eye, where vision is blurred by an irregularly shaped cornea. ...

• They correct for both spherical and cylindrical aberration.
• They may 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 thicker at the bottom and this thicker zone is pushed down by the upper eyelid during blinking to allow the lens to rotate into the correct position (with this thicker zone at the 6 o'clock position on the eye). Toric lenses are usually marked with tiny striations to assist their fitting.
• They are usually more expensive to produce than non-toric lenses; therefore they are usually meant for extended wear. The first disposable toric lenses were introduced in 2000 by Vistakon.

Like eyeglasses, contact lenses can have one (single vision) or more (multifocal) focal points. The Acuvue brand of contact lenses, made by Vistakon, a subsidiary of Johnson & Johnson, is among the worlds most popular brands of disposable contact lenses. ... An image that is partially in focus, but mostly out of focus in varying degrees. ...

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^[35]: 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. Presbyopia (Greek word presbyteros (πρεσβύτερος), meaning elder) is the eyes diminished ability to focus that occurs with aging. ... Accommodative insufficiency (AI) involves the inability of the eye to focus properly on an object. ...

Rigid gas permeable bifocal 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. RGPs must translate (move vertically) to work properly, and thus the gaze of the eye can change from the near to the distant sections, much like bifocal eyeglasses.

Multifocal soft 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 corrections are presented simultaneously to the retina, regardless of the position of the eye. Of course, only one correction is correct, the incorrect correction causes blur. Commonly these are designed with distance correction in the center of the lens and near correction in the periphery, or vice versa.

Implantation

Intraocular 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 degrees of myopia and hyperopia. An intraocular lens (IOL) is an implanted lens in the eye, usually replacing the existing crystalline lens because it has been clouded over by a cataract, or as a form of refractive surgery to change the eyes optical power. ... The posterior chamber is a narrow chink behind the peripheral part of the iris, and in front of the suspensory ligament of the lens and the ciliary processes. ... In anatomy, the iris (plural irises or irides) is the most visible part of the eye of vertebrates, including humans. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ...

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.^[36]
• Lathe cut - A lathe cut contact lens is cut and ground on a lathe.^[36]
• Molded
• Hybrids

Although many companies make contact lenses, there are four major manufacturers: Vistakon/Johnson & Johnson, CIBA Vision, Bausch & Lomb, and CooperVision.^[37] For other uses, see Lathe (disambiguation). ... The Acuvue brand of contact lenses, made by Vistakon, a subsidiary of Johnson & Johnson, is among the worlds most popular brands of disposable contact lenses. ... Johnson & Johnson (NYSE: JNJ) is a global American pharmaceutical, medical devices and consumer packaged goods manufacturer founded in 1886. ... CIBA Vision, a Novartis company is a contact lens provider and is the eye-care unit of Novartis AG. It is headquartered in Atlanta, Georgia (USA) in the Johns Creek Technology Park. ... Bausch & Lomb is an American company based in Rochester, New York, specializing in eye health products such as contact lenses, lens care products and eye surgery devices and instruments. ... CooperVision is the 3rd largest contact lens maker in the world and the number one manufacturer of toric lenses. ...

Contact lens prescriptions

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. An eye care professional is an individual who provides a service related to the eyes or vision. ... // COUNCIL DIRECTIVE 93/42/EEC of 14 June 1993 concerning medical devices defines a ‘medical device’ as: any instrument, apparatus, appliance, material or other article, whether used alone or in combination, including the software necessary for its proper application intended by the manufacturer to be used for human beings for... Optometry is a doctoral-degree health care profession concerned with eyes and related structures, as well as vision, visual systems, and vision information processing in humans. ... This article is about the branch of medicine. ... An optician is to an ophthalmologist and optometrist as a pharmacist is to a physician. ... A pair of modern glasses Glasses, also called eyeglasses or spectacles are frames, bearing lenses worn in front of the eyes normally for vision correction, eye protection, or for protection from UV rays. ...

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. Especially above the age of 35 years dry eyes often makes wearing contact lenses too risky, especially soft lenses. Traditional Snellen chart used for visual acuity testing. ... Keratoconjunctivitis sicca or KCS is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in people and small animals. ... Keratoconjunctivitis sicca or KCS is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in people and small animals. ...

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

Many people already wearing contact lenses order contact lenses over the internet at their own risk. In the US, The Fairness to Contact Lens Consumers Act, which became law in February, 2004, was intended to ensure the availability of contact lens prescriptions to patients ^[38]. Under the law consumers have a right to obtain a copy of their contact lens prescription, allowing them to fill that prescription at the business of their choice. Oxygen permeability, abbreviated Dk, is a parameter of a contact lens. ... Base curve radius, or BCR, is a parameter of a contact lens. ... DIAMETER is a computer networking protocol for AAA (Authentication, Authorization and Accounting). ... Optical power or dioptric power or refractive power is the degree to which a lens or mirror converges or diverges light. ... A dioptre, or diopter, is a non-SI unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres (i. ...

Complications

Complications due to contact lens wear affect roughly 4% of contact lens wearers each year.^[39] Excessive wear of contact lenses, particularly overnight wear, is associated with most of the 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.^[39] Complication, in medicine, is a unfavorable evolution of a disease, a health condition or a medical treatment. ... An eyelid is a thin fold of skin that covers and protects an eye. ... Image of a human eye clearly showing the blood vessels of the conjuntiva. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... The tear system. ...

Eyelid:

• Ptosis

Conjunctiva: In ophthalmology, ptosis is an abnormally low position (drooping) of the upper eyelid which may grow more or less severe during the day. ...

• Contact dermatitis
• Giant papillary conjunctivitis
• Superior limbic keratoconjunctivitis

Cornea: Contact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants. ... Conjunctivitis (commonly called pinkeye) is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), often due to infection. ... Conjunctivitis (commonly called pinkeye) is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), often due to infection. ...

• Epithelium

• Corneal abrasion
• Corneal erosion
• Corneal ulcer
• Hypoxia

• Stroma

• Infection and keratitis

• Bacteria
• Protozoa: Acanthamoeba
• Fungal: Fusarium^[40]

• Contact lens acute red eye (CLARE)
• Keratoconus

• Endothelium

This article is about the epithelium as it relates to animal anatomy. ... For corneal abrasions in dogs and cats, see corneal ulcer. ... Recurrent corneal erosion is a painful disorder of the eyes involving the outermost corneal layer. ... A corneal ulcer is an inflammatory condition of the cornea involving loss of its outer layer. ... Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. ... Stroma can refer to: The connective supportive framework of a biological cell, tissue, or organ. ... An infection is the detrimental colonization of a host organism by a foreign species. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Leishmania donovani, (a species of protozoan) in a bone marrow cell (in Greek proto = first and zoa = animals) are one-celled eukaryotes (that is, unicellular microbes whose cells have membrane-bound nuclei) that commonly show characteristics usually associated with animals, mobility and heterotrophy. ... Acanthamoeba is a genus of amoebae, one of the most common protozoa in soil, and also frequently found in freshwater and other habitats. ... Fusarium is a large genus of filamentous fungi widely distributed in soil and in association with plants. ... Keratitis is a condition in which the eyes cornea is inflamed. ... Keratoconus (from Greek: kerato- horn, cornea; and konos cone), is a degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve. ... The endothelium is the layer of thin, flat cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. ...

Usage

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. The soap should not be antibacterial due to risk of improper hand washing and the possibility of destroying the natural bacteria found on the eye. These bacteria keep pathogenic bacteria from colonizing the cornea. The technique for removing or inserting a contact lens varies slightly depending upon whether the lens is soft or rigid. Hand washing is the act of cleansing the hands with water or other liquid, with or without the use of soap or other detergents, for the purpose of removing soil or microorganisms. ... For other uses, see Soap (disambiguation). ... Moisturizers are a complex mixture of chemical agents specially designed to make the external layers of the skin (epidermis) softer and more pliable, by increasing its hydration (water content). ... An allergen is any substance (antigen), most often eaten or inhaled, that is recognized by the immune system and causes an allergic reaction. ... Odor receptors on the antennae of a Luna moth An odor is the object of perception of the sense of olfaction. ... An antiseptic is a substance that kills or prevents the growth of bacteria on the external surfaces of the body. ...

Insertion

Contact lenses are typically inserted into the eye by placing them on the index finger with the concave side upward and raising them to touch the cornea. The other hand may be employed to keep the eye open. Problems may arise particularly with disposable soft lenses; if the surface tension between the lens and the finger is too great the lens may turn itself inside out; alternatively it may fold itself in half. When the lens first contacts the eye, a brief period of irritation may ensue as the eye acclimatises to the lens and also (if a multi-use lens is not correctly cleansed) as dirt on the lens irritates the eye. Irrigation may help during this period, which generally should not exceed one minute. This box:      Surface tension is a property of the surface of a liquid that causes it to behave as an elastic sheet. ...

Removal

A soft lens may be removed by holding the eyelids open and grasping the lens with opposing digits. This method can cause irritation, could risk damage to the eye and may in many cases be difficult, in part due to the blink reflex. If the lens is pushed off the cornea it will buckle up (due to the difference in curvature), making it easier to grasp. Corneal reflex This is an automated involuntary blinking of the eyelids (See : Reflex) elicited by stimulation (such as touching or a foreign body) of the eyeballs cornea. ...

Rigid contact lenses may be removed by pulling with one finger on the outer or lateral canthus, then blinking to cause the lens to lose adhesion. The other hand is typically cupped underneath the eye to catch the lens. There also exist small tools specifically for removing lenses, which resemble small plungers made of flexible plastic; the concave end is raised to the eye and touched to the lens, forming a seal stronger than that of the lens with the cornea and allowing the lens to be removed from the eye. Front of left eye with eyelids separated to show medial canthus. ... Dew drops adhering to a spider web For the medical condition see Adhesion (medicine) Adhesion is the molecular attraction exerted between bodies in contact. ... For the coffee plunger, see French press. ...

Care (cleaning and disinfection)

Lens cover to store contact lens

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: Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution‎ (1,752 × 1,168 pixels, file size: 869 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution‎ (1,752 × 1,168 pixels, file size: 869 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Acanthamoeba is a genus of amoebae, one of the most common protozoa in soil, and also frequently found in freshwater and other habitats. ... Staphylococcus aureus biofilm on an indwelling catheter. ...

• 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 protein removal enzyme tablets in most cases. Some multipurpose solutions are not effective at disinfecting Acanthamoeba from the lens.^[41] In May 2007, one brand of multipurpose solution was recalled due to a cluster of Acanthamoeba infections.^[42][43] Newer generations of multipurpose solutions, such as OPTI-FREE RepleniSH are effective against bacteria, fungi, and acanthamoeba and are designed to condition the lenses while soaking.
• 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 be used to rinse away the peroxide. If you get this solution in your eyes, it is highly recommended that you go to the Emergency Room and get your eye(s) irrigated.^[44]
• 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. In addition, one should remember to wash the contact cases or lens covers thoroughly with water and multipurpose solution or hydrogen peroxide to avoid formation of biofilms on its surfaces. Acanthamoeba is a genus of amoebae, one of the most common protozoa in soil, and also frequently found in freshwater and other habitats. ... In medicine, saline is a solution of sodium chloride (a substance also commonly known as table salt) in sterile water, used frequently for intravenous infusion, rinsing contact lenses, and nasal irrigation (or the yogic practice called jala neti). ...

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 thiomersal, benzalkonium chloride, benzyl alcohol, and other compounds. In 1989, thiomersal was responsible for about 10% of problems related to contact lenses^[45]: 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. The introduction of silicone-hydrogel soft contact lens materials in 1999 made selection of the proper disinfecting solution more important. One study has noted several incompatibilities between these new lens materials and some solutions resulting in corneal staining.^[46] A cluster of Escherichia coli bacteria magnified 10,000 times. ... This article does not cite any references or sources. ... Thiomersal (INN) (C9H9HgNaO2S), formerly and still commonly known in the United States as thimerosal, is an organomercury compound (approximately 49% mercury by weight) used as an antiseptic and antifungal agent. ... R-phrases , , S-phrases , , RTECS number BO3150000 Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Benzalkonium chloride (alkyl dimethyl benzyl ammonium chloride) is a mixture of alkylbenzyl dimethylammonium chlorides of various alkyl chain lengths. ... Benzyl alcohol, also known as phenylmethanol, is a clear, colorless liquid with a mild pleasant aromatic odor. ... Shelf-life is the length of time that corresponds to a tolerable loss in quality of a processed food. ...

Current research

A large segment of current contact lens research is directed towards the treatment and prevention of conditions resulting from contact lens contamination and colonization by foreign organisms. It is generally accepted by clinicians that the most significant complication of contact lens wear is microbial keratitis and that the most predominant microbial pathogen is Pseudomonas aeruginosa ^[47]. Other organisms are also major causative factors in bacterial keratitis associated with contact lens wear, although their prevalence varies across different locations. These include both the Staphylococcus species (aureus and epidermidis) and the Streptococcus species, among others ^[48][49]. Microbial keratitis is a serious focal point of current research due to its potentially devastating effect on the eye, including severe vision loss ^[50]. Binomial name Pseudomonas aeruginosa (Schroeter 1872) Migula 1900 Synonyms Bacterium aeruginosum Schroeter 1872 Bacterium aeruginosum Cohn 1872 Micrococcus pyocyaneus Zopf 1884 Bacillus aeruginosus (Schroeter 1872) Trevisan 1885 Bacillus pyocyaneus (Zopf 1884) Flügge 1886 Pseudomonas pyocyanea (Zopf 1884) Migula 1895 Bacterium pyocyaneum (Zopf 1884) Lehmann and Neumann 1896 Pseudomonas polycolor... Staphylococcus (in Greek staphyle means bunch of grapes and coccos means granule) is a genus of Gram-positive bacteria. ... Species S. agalactiae S. bovis S. mutans S. pneumoniae S. pyogenes S. salivarius S. sanguinis S. suis Streptococcus viridans Streptococcus uberis etc. ...

One specific research topic of interest is how microbes such as Pseudomonas aeruginosa invade the eye and cause infection. Although the pathogenesis of microbial keratitis is not well understood, many different factors have been investigated. One group of researchers showed that corneal hypoxia exacerbated Pseudomonas binding to the corneal epithelium, internalization of the microbes, and induction of the inflammatory response ^[51]. One way to alleviate hypoxia is to increase the amount of oxygen transmitted to the cornea. Although silicone-hydrogel lenses almost eliminate hypoxia in patients due to their very high levels of oxygen transmissibility ^[52], they also seem to provide a more efficient platform for bacterial contamination and corneal infiltration than other conventional hydrogel soft contact lenses. A recent study showed that Pseudomonas aeruginosa and Staphylococcus epidermis adhere much more strongly to silicone hydrogel contact lenses than conventional hydrogel contact lenses and that adhesion of Pseudomonas aeruginosa was 20 times stronger than adhesion of Staphylococcus epidermidis ^[53]. This might help to explain one reason why Pseudomonas infections are the most predominant. Binomial name Pseudomonas aeruginosa (Schroeter 1872) Migula 1900 Synonyms Bacterium aeruginosum Schroeter 1872 Bacterium aeruginosum Cohn 1872 Micrococcus pyocyaneus Zopf 1884 Bacillus aeruginosus (Schroeter 1872) Trevisan 1885 Bacillus pyocyaneus (Zopf 1884) Flügge 1886 Pseudomonas pyocyanea (Zopf 1884) Migula 1895 Bacterium pyocyaneum (Zopf 1884) Lehmann and Neumann 1896 Pseudomonas polycolor... Hypoxia may refer to: Hypoxia (medical), the lack of oxygen in tissues Hypoxia or Oxygen depletion, a reduced concentration of dissolved oxygen in a water body leading to stress or even death in aquatic organisms This is a disambiguation page: a list of articles associated with the same title. ... Binomial name Pseudomonas aeruginosa (Schroeter 1872) Migula 1900 Synonyms Bacterium aeruginosum Schroeter 1872 Bacterium aeruginosum Cohn 1872 Micrococcus pyocyaneus Zopf 1884 Bacillus aeruginosus (Schroeter 1872) Trevisan 1885 Bacillus pyocyaneus (Zopf 1884) Flügge 1886 Pseudomonas pyocyanea (Zopf 1884) Migula 1895 Bacterium pyocyaneum (Zopf 1884) Lehmann and Neumann 1896 Pseudomonas polycolor...

Another important area of contact lens research deals with patient compliance. Compliance is a major issue surrounding the use of contact lenses because patient noncompliance often leads to contamination of the lens, storage case, or both ^[54][55][56]. The introduction of multipurpose solutions and daily disposable lenses have helped to alleviate some of the problems observed from inadequate cleaning but new methods of combating microbial contamination are currently being developed. A silver-impregnated lens case has been developed which helps to eradicate any potentially contaminating microbes that come in contact with the lens case ^[57]. Additionally, a number of antimicrobial agents are being developed that have been embedded into contact lenses themselves. Contact lenses with covalently attached Selenium molecules have been shown to reduce bacterial colonization without adversely affecting the cornea of a rabbit eye ^[58] and octylglucoside used as a contact lens surfactant significantly decreases bacterial adhesion ^[59]. These compounds are of particular interest to contact lens manufacturers and prescribing optometrists because they do not require any patient compliance to effectively attenuate the effects of bacterial colonization. This article is about the chemical element. ... An antimicrobial is a substance that kills or inhibits the growth of microbes such as bacteria. ... For other uses, see Selenium (disambiguation). ...

See also

• Bionic contact lens
• Corrective lens
• Eyeglass prescription
• Visual acuity

A bifocal corrective eyeglasses lens A corrective lens is a lens worn in front of the eye, mainly used to treat myopia, hyperopia, astigmatism, and presbyopia. ... Using a phoropter to determine a prescription for eyeglasses An eyeglass prescription is a written order by an ophthalmologist or an optometrist to an optician for eyeglasses. ... Traditional Snellen chart used for visual acuity testing. ...

Brands

• Acuvue
• Advanced Medical Optics
• Bausch & Lomb
• CooperVision
• CIBA Vision
• UltraVision
• Wöhlk

The Acuvue brand of contact lenses is among the worlds most popular brands of disposable contact lenses. ... Advanced Medical Optics, Inc. ... Bausch & Lomb is an American company based in Rochester, New York, specializing in eye health products such as contact lenses, lens care products and eye surgery devices and instruments. ... CooperVision is the 3rd largest contact lens maker in the world and the number one manufacturer of toric lenses. ... CIBA Vision, a Novartis company is a contact lens provider and is the eye-care unit of Novartis AG. It is headquartered in Atlanta, Georgia (USA) in the Johns Creek Technology Park. ... UltraVision CLPL is a contact lens manufacturer, with headquarters based in Leighton Buzzard, Bedfordshire, England. ...

References and sources

Sources:

• Efron, Nathan (2002). Contact Lens Practice, Elsevier Health Sciences. ISBN 0-7506-4690-X.

References:

is the 59th day of the year in the Gregorian calendar. ... Year 1948 (MCMXLVIII) was a leap year starting on Thursday (link will display the 1948 calendar) of the Gregorian calendar. ... is the 245th day of the year (246th in leap years) in the Gregorian calendar. ... Year 1949 (MCMXLIX) was a common year starting on Saturday (link will display the full calendar) of the Gregorian calendar. ... is the 252nd day of the year (253rd in leap years) in the Gregorian calendar. ... Year 1949 (MCMXLIX) was a common year starting on Saturday (link will display the full calendar) of the Gregorian calendar. ... The New York Times is a daily newspaper published in New York City and distributed internationally. ... is the 42nd day of the year in the Gregorian calendar. ... Year 1952 (MCMLII) was a leap year starting on Tuesday (link will display full calendar) of the Gregorian calendar. ... It has been suggested that Health Care Financing Administration be merged into this article or section. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 60th day of the year (61st in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 219th day of the year (220th in leap years) in the Gregorian calendar. ... The Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, is recognized as the leading United States agency for protecting the public health and safety of people. ...

External links

Wikimedia Commons has media related to:

Contact lens

• British Contact Lens Association
• Contact Lens & Anterior Eye Journal
• Contact Lens History