question: how do contact lenses work to help you see?
comment: Normal sight is made possible partly because of the part of your eye called the lens. It is an oblong shaped piece of clear tissue that bends light. It is shaped in such a way that light entering from various angles is all bent so that they hit the same spot on the retina on the back of your eye. Eye sight problems can be caused when this lens is not shaped correctly, meaning light does not bend all the way, or bends too much. Artificial lenses, like contacts and glasses, fix this by bending the light as well, in such a way that when it hits the natural lens of your eye, it is able to bend it appropriately to hit your retina in the right spot to focus one the image.
passages: 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 and his assistant Drahoslav Lím, who also invented the first gel used for their production.
   Contact lenses usually serve the same corrective purpose as 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. Lenses now have a slight bluish tint which is a thin UV coating; this reduces glare and cornea damage much like a pair of sunglasses.
  
  Section::::Surgical Vision Correction.
  
  Section::::Surgical Vision Correction.:Photorefractive keratectomy.
   A small number of hybrid lenses exist. Typically these contact lenses consist of a rigid center and a soft "skirt". A similar technique is the "piggybacking" of a smaller, rigid lens on the surface of a larger, soft lens. These techniques are often chosen to give the vision correction benefits of a rigid lens and the comfort of a soft lens.
  
  Section::::Types.:Wear schedule.
   Corrective contact lenses are designed to improve vision, most commonly by correcting refractive error. This is done by directly focusing light so it enters the eye with the proper power for clear vision.
   Section::::Usage.:Removal.
   Section::::Current research.
   Alternatively, a person may simply wear reading glasses over their distance contact lenses.
  
  Section::::Types.:Functions.:Corrective contact lenses.:Other types of vision correction.
  
  For those with certain color deficiencies, a red-tinted "X-Chrom" contact lens may be used. Although such a lens does not restore normal color vision, it allows some color-blind people to distinguish colors better. Red-filtering contact lenses can also be an option for extreme light sensitivity in some visual deficiencies such as achromatopsia.
   A recent area of research is in the field of bionic lenses. These are visual displays that include built-in electric circuits and light-emitting diodes and can harvest radio waves for their electric power. Bionic lenses can display information beamed from a mobile device overcoming the small display size problem. The technology involves embedding nano and microscale electronic devices in lenses. These lenses will also need to have an array of microlenses to focus the image so that it appears suspended in front of the wearer’s eyes. The lens could also serve as a head-up display for pilots or gamers.
   Magnification is another area being researched for future contact lens applications. Embedding of telescopic lenses and electronic components suggests that future uses of contact lenses may become extremely diverse. 
  
  Section::::Types.:Functions.:Cosmetic contact lenses.
  
  A cosmetic contact lens is designed to change the appearance of the eye. These lenses may also correct refractive error. Although many brands of contact lenses are lightly tinted to make them easier to handle, cosmetic lenses worn to change eye color are far less common, accounting for only 3% of contact lens fits in 2004.
   Cosmetic lenses can have more direct medical applications. For example, some contact lenses can restore the appearance and, to some extent the function, of a damaged or missing iris.
  
  Section::::Types.:Functions.:Therapeutic scleral lenses.
   Drug administration through contact lenses is also becoming an area of research. One application is a lens that releases anesthesia to the eye for post-surgery pain relief, especially after PRK (photorefractive keratectomy) in which the healing process takes several days. One experiment shows that silicone contact lenses that contain vitamin E deliver pain medication for up to seven days compared with less than two hours in usual lenses.
   There are many ways to clean and care for contact lenses, typically called care systems or lens solutions:
  
  BULLET::::- Multipurpose solutions
  
  BULLET::::- Hydrogen peroxide systems
  
  BULLET::::- 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.
   A "daily wear" (DW) contact lens is designed to be worn for one day and removed before sleeping. An "extended wear" (EW) contact lens is designed for continuous overnight wear, typically for up to 6 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). EW and CW contact lenses can be worn overnight because of their high oxygen permeability. While awake, the eyes are mostly open, allowing oxygen from the air to dissolve into the tears and pass through the lens to the cornea. While asleep, oxygen is supplied from the blood vessels in the back of the eyelid. A lens hindering passage of oxygen to the cornea causes corneal hypoxia which can result in serious complications, such as corneal ulcer that, if left untreated, can permanently decrease vision. EW and CW contact lenses typically allow for a transfer of 5–6 times more oxygen than conventional softs, allowing the cornea to remain healthy, even with closed eyelids.
   People choose to wear contact lenses for many reasons. Aesthetics and cosmetics are the main motivating factors for people who want to avoid wearing glasses or to change the appearance of their eyes. Others wear contact lenses for functional or optical reasons. When compared with spectacles, contact lenses typically provide better peripheral vision, and do not collect moisture (from rain, snow, condensation etc.) or perspiration. This can make them preferable for sports and other outdoor activities. Contact lens wearers can also wear sunglasses, goggles, or other eyewear of their choice without having to fit them with prescription lenses or worry about compatibility with glasses. Additionally, there are conditions such as keratoconus and aniseikonia that are typically corrected better with contact lenses than with glasses.
   Correction of presbyopia (a need for a reading prescription different from the prescription needed for distance) presents an additional challenge in the fitting of contact lenses. Two main strategies exist: multifocal lenses and monovision.
  
  Multifocal contact lenses (e.g. bifocals or progressives) are comparable to spectacles with bifocals or progressive lenses because they have multiple focal points. Multifocal contact lenses are typically designed for constant viewing through the center of the lens, but some designs do incorporate a shift in lens position to view through the reading power (similar to bifocal glasses).
   Current brands of soft lenses are either traditional hydrogel or silicone hydrogel. Because of drastic differences in oxygen permeability, replacement schedule, and other design characteristics, it is very important to follow the instructions of the eye care professional prescribing the lenses.
  
  Section::::Types.:Materials.:Hybrid.
   Contact lenses are typically inserted into the eye by placing them on the pad of the index or middle finger with the concave side upward and then using that finger to place the lens on the eye. Rigid lenses should be placed directly on the cornea. Soft lenses may be placed on the sclera (white of the eye) and then slid into place. Another finger of the same hand, or a finger of the other hand, is used to keep the eye wide open. Alternatively, the user may close their eyes and then look towards their nose, sliding the lens into place over the cornea. Problems may arise if the lens folds, turns inside-out, slides off the finger prematurely, or adheres more tightly to the finger than the eye surface. A drop of solution may help the lens adhere to the eye.
   Section::::Types.:Functions.:Therapeutic soft lenses.
  
  Soft lenses are often used in the treatment and management of non-refractive disorders of the eye. A bandage contact lens allows the patient to see while protecting an injured or diseased cornea from the constant rubbing of blinking eyelids, thereby allowing it to heal. They are used in the treatment of conditions including bullous keratopathy, dry eyes, corneal abrasions and erosion, keratitis, corneal edema, descemetocele, corneal ectasis, Mooren's ulcer, anterior corneal dystrophy, and neurotrophic keratoconjunctivitis. Contact lenses that deliver drugs to the eye have also been developed.
  
  Section::::Types.:Materials.
  
  Section::::Types.:Materials.:Rigid lenses.
   Biotrue contact lens solutions are a brand of cleaning and storage solutions manufactured by Bausch & Lomb that were developed to match the natural lubricant found in the eye. It matches the pH of healthy tears and helps to keep certain beneficial tear proteins active while removing deposited proteins that distort a wearers vision. In theory this helps to keep a users contact lenses more comfortable. In 2012 an affordable line of daily disposable contact lenses were launched under the same brand name for both single vision and for users with presbyopia. They were first introduced in Italy and quickly followed by the United Kingdom and the Nordics. In 2015 they were approved for the US market. Biotrue one day contact lenses are made from a material called HyperGel and manufactured in the country of Ireland.
   Pesudovs is trained in Contact Lenses (under AJ Phillips).
  
  Section::::Honours.
   A rigid lens is able to cover the natural shape of the cornea with a new refracting surface. This means that a spherical rigid contact lens can correct corneal astigmatism. Rigid lenses can also be made as a front-toric, back-toric, or bitoric. Rigid lenses can also correct corneas with irregular geometries, such as those with keratoconus or post surgical ectasias. In most cases, patients with keratoconus see better through rigid lenses than through glasses. Rigid lenses are more chemically inert, allowing them to be worn in more challenging environments than soft lenses.
  
  Section::::Types.:Materials.:Soft lenses.
   A contact lens, or simply contact, is a thin lens placed directly on the surface of the eye. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision, for cosmetic, or therapeutic reasons. In 2004, it was estimated that 125 million people worldwide use contact lenses, including 28 to 38 million in the United States. In 2010, the worldwide market for contact lenses was estimated at $6.1 billion, while the US soft lens market was estimated at $2.1 billion. Multiple analysts estimated that the global market for contact lenses would reach $11.7 billion by 2015. , the average age of contact lens wearers globally was 31 years old, and two-thirds of wearers were female.
   Doctors discovered the reshaping phenomena of glass lenses as early as the 1940s. This history of orthokeratology includes contributions made by multiple authors to the use of contact lenses for myopia reduction.
   Wesley and Jessen eventually developed the plastic lenses known as rigid contact lenses. The lens fit over just the cornea, unlike its predecessor, which also rested on the sclera (the white area), said Neil Hodur, a professor at the Illinois College of Optometry and a colleague and friend of Dr. Wesley's. The end product was lenses that were smaller, thinner and longer-wearing, said Alfred Rosenbloom, a former dean and president of the Illinois College of Optometry.
   Scleral lens
  
  A scleral lens, also known as a scleral contact lens and ocular surface prostheses is a large contact lens that rests on the sclera and creates a tear-filled vault over the cornea. Scleral lenses are designed to treat a variety of eye conditions, many of which do not respond to other forms of treatment.
  
  Section::::Uses.
  
  Section::::Uses.:Medical uses.
  