Editing Contact lens (section)

==Types==
Contact lenses are classified in diverse ways, namely, by their primary function, material, wear schedule (how long a lens can be worn), and replacement schedule (how long before a lens needs to be discarded).

===Functions===

====Correction of refractive error====
[[Corrective lens|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 [[Dioptre|power]] for clear vision.

A spherical contact lens bends light evenly in every direction (horizontally, vertically, etc.). They are typically used to correct [[myopia]] and [[hypermetropia]].

There are two ways that contact lenses can correct astigmatism. One way is with [[toric lens|toric]] soft lenses that work essentially the same way as eyeglasses with cylindrical correction; a toric lens has a different focusing power horizontally than vertically, and as a result can correct for [[astigmatism]]. Another way is by using a rigid gas permeable lens; since most astigmatism is caused by the shape of the cornea, rigid lenses can improve vision because the front surface of the optical system is the perfectly spherical lens.<ref>{{Cite web |title=Astigmatism |url=http://www.aoa.org/Astigmatism.xml,%20http://www.aoa.org/Astigmatism.xml |access-date=2020-08-06 |website=www.aoa.org |language=en}}{{Dead link|date=December 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Both approaches have advantages and drawbacks. Toric lenses must have the proper orientation to correct for astigmatism, so such lenses must have additional design characteristics to prevent them from rotating out of alignment. This can be done by weighting the bottom of the lens or by using other physical characteristics to rotate the lens back into position, but these mechanisms rarely work perfectly, so some misalignment is common and results in somewhat imperfect correction, and blurring of sight after blinking rotates the lens. Toric soft lenses have all the advantages of soft lenses in general, which are low initial cost, ease of fitting, and minimal adjustment period. Rigid gas permeable lenses usually provide superior optical correction but have become less popular relative to soft lenses due to higher initial costs, longer initial adjustment period, and more involved fitting.<ref>{{Cite web |title=Advantages and Disadvantages of Various Types of Contact Lenses |url=https://www.aoa.org/patients-and-public/caring-for-your-vision/contact-lenses/advantages-and-disadvantages-of-various-types-of-contact-lenses |access-date=2020-08-06 |website=www.aoa.org |language=en}}</ref><ref>{{Cite web |date=2013-01-26 |title=A Complete Guide to Gas Permeable Contact Lenses |url=https://www.eyehealthweb.com/rigid-gas-permeable-lenses/ |access-date=2020-08-06 |website=EyeHealthWeb.com |language=en}}</ref>

====Correction of presbyopia====
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 lens]]es because they have multiple [[focus (optics)|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).

Monovision<ref>{{Cite journal |last=Lebow |first=KA |last2=Goldberg |first2=JB |year=1975 |title=Characteristic of binocular vision found for presbyopic patients wearing single vision contact lenses |journal=Journal of the American Optometric Association |volume=46 |issue=11 |pages=1116–23 |pmid=802938}}</ref> is the use of single-vision lenses (one focal point per lens) to focus an eye (typically the dominant one) for distance vision and the other for near work. The brain then learns to use this setup to see clearly at all distances. A technique called modified monovision uses multifocal lenses and also specializes one eye for distance and the other for near, thus gaining the benefits of both systems. Care is advised for persons with a previous history of [[strabismus]] and those with significant phorias, who are at risk of eye misalignment under monovision.<ref>{{Cite journal |last=Pollard |first=Zane F. |last2=Greenberg |first2=Marc F. |last3=Bordenca |first3=Mark |last4=Elliott |first4=Joshua |last5=Hsu |first5=Victoria |date=September 2011 |title=Strabismus Precipitated by Monovision |journal=American Journal of Ophthalmology |volume=152 |issue=3 |pages=479–482.e1 |doi=10.1016/j.ajo.2011.02.008 |pmid=21669405}}</ref>   Studies have shown no adverse effect to driving performance in adapted monovision contact lens wearers.<ref>{{Cite journal |last=Wood |first=Joanne M. |last2=Wick |first2=Kristan |last3=Shuley |first3=Vicki |last4=Pearce |first4=Brendon |last5=Evans |first5=Dean |date=6 May 1998 |title=The effect of monovision contact lens wear on driving performance |journal=Clinical and Experimental Optometry |volume=81 |issue=3 |pages=100–103 |doi=10.1111/j.1444-0938.1998.tb06727.x |pmid=12482258 |s2cid=38392636}}</ref>

Alternatively, a person may simply wear reading glasses over their distance contact lenses.

====Other types of vision correction====
For those with certain [[color blindness|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.<ref>{{Cite journal |last=Hartenbaum |first=NP |last2=Stack |first2=CM |year=1997 |title=Color vision deficiency and the X-Chrom lens |journal=Occupational Health & Safety |volume=66 |issue=9 |pages=36–40, 42 |pmid=9314196}}</ref><ref>{{Cite journal |last=Siegel |first=IM |year=1981 |title=The X-Chrom lens. On seeing red |journal=Survey of Ophthalmology |volume=25 |issue=5 |pages=312–24 |doi=10.1016/S0039-6257(81)80001-X |pmid=6971497}}</ref> Red-filtering contact lenses can also be an option for extreme light sensitivity in some visual deficiencies such as [[achromatopsia]].<ref>http://www.achromatopsia.info/red-contact-lenses/ Red contact lenses for achromats</ref>

ChromaGen contact lenses have been used and shown to have some limitations with vision at night although otherwise producing significant improvements in color vision.<ref>{{Cite journal |last=Swarbrick |first=HA |last2=Nguyen |first2=P |last3=Nguyen |first3=T |last4=Pham |first4=P |year=2001 |title=The ChromaGen contact lens system: Colour vision test results and subjective responses |journal=Ophthalmic & Physiological Optics |volume=21 |issue=3 |pages=182–96 |doi=10.1046/j.1475-1313.2001.00583.x |pmid=11396392 |s2cid=40409461}}</ref> An earlier study showed very significant improvements in color vision and patient satisfaction.<ref>Harris D "Colouring Sight: A study of CL fittings with colour enhancing lenses" 'Optician' 8 June 1997</ref>

Later work that used these ChromaGen lenses with [[Dyslexia|people with dyslexia]] in a randomised, double-blind, placebo-controlled trial showed highly significant{{Clarify|reason=vague|date=June 2017}} improvements in reading ability over reading without the lenses.<ref>Harris DA, MacRow-Hill SJ "Application of ChromaGen haploscopic lenses to patients with dyslexia: a double masked placebo controlled trial" Journal of the American Optometric Association 25/10/99.</ref> This system has been granted FDA approval for use in the United States.<ref>{{Cite press release |title=Cision - FDA Cleared ChromaGen Lenses |url=https://www.prnewswire.com/news-releases/fda-cleared-chromagen-lenses-are-a-life-changing-aid-for-people-struggling-with-dyslexia-and-other-reading-problems-200289391.html |url-status=live |archive-url=https://web.archive.org/web/20130703043949/http://www.prnewswire.com/news-releases/fda-cleared-chromagen-lenses-are-a-life-changing-aid-for-people-struggling-with-dyslexia-and-other-reading-problems-200289391.html |archive-date=3 July 2013}}</ref>

[[Magnification]] is another area being researched for future contact lens applications.<ref>{{Cite magazine |title=Telescopic contact lens magnifies vision by 2.8 times on demand |url=https://www.wired.co.uk/news/archive/2013-07/24/magnifying-contact-lenses |url-status=dead |archive-url=https://web.archive.org/web/20150402151345/http://www.wired.co.uk/news/archive/2013-07/24/magnifying-contact-lenses |archive-date=2 April 2015 |access-date=26 March 2015 |magazine=Wired UK}}</ref> Embedding of telescopic lenses and electronic components suggests that future uses of contact lenses may become extremely diverse.

====Cosmetic contact lenses====
[[File:Contact Grain.jpg|thumb|Woman wearing a cosmetic type of contact lens; enlarged detail shows the grain produced during the manufacturing process. Curving of the lines of printed dots suggests these lenses were manufactured by printing onto a flat sheet then shaping it.]]

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.<ref>Morgan PB et al.[http://www.clspectrum.com/article.aspx?article=12741 "International Contact Lens Prescribing in 2004: An analysis of more than 17,000 contact lens fits from 14 countries in 2004 reveals the diversity of contact lens practice worldwide."] ''Contact Lens Spectrum.'' January 2005.</ref>

In the United States, the FDA labels non-corrective cosmetic contact lenses as ''decorative contact lenses''. Like any contact lens, cosmetic lenses carry risks of mild to serious complications, including ocular redness, irritation and infection.<ref>[http://www.mc.vanderbilt.edu/news/releases.php?release=1670 Vanderbilt University Medical Center – Vanderbilt Eye Doctors Warn of the Dangers of Cosmetic Contact Lenses]. Mc.vanderbilt.edu (19 April 2010). Retrieved on 2013-07-21.</ref>

Due to their medical nature, colored contact lenses, similar to regular ones, are illegal to purchase in the United States without a valid prescription. Those with perfect vision can buy color contacts for cosmetic reasons, but they still need their eyes to be measured for a "plano" prescription, meaning one with zero vision correction. This is for safety reasons so the lenses will fit the eye without causing irritation or redness.

Some colored contact lenses completely cover the iris, thus dramatically changing eye color. Other colored contact lenses merely tint the iris, highlighting its natural color. A new trend in Japan, South Korea and China is the [[circle contact lens]], which extend the appearance of the iris onto the sclera by having a dark tinted area all around. The result is an appearance of a bigger, wider iris, a look reminiscent of dolls' eyes.<ref>{{Cite web |title=How Do You Find the Right Circle Lens? |url=http://www.eyecandys.com/news/finding-the-right-circle-lenses |url-status=dead |archive-url=https://web.archive.org/web/20131213060734/http://www.eyecandys.com/news/finding-the-right-circle-lenses |archive-date=13 December 2013 |access-date=26 March 2015 |website=EyeCandy's}}</ref>

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 [[aniridia|missing]] [[Iris (anatomy)|iris]].

====Therapeutic scleral lenses====
[[File:Scleral lens worn on an eye.jpg|thumb|upright|alt=See caption|[[Scleral lens]], with visible outer edge resting on the sclera of a patient with severe [[dry eye syndrome]] ]]

A [[scleral lens]] is a large, firm, transparent, oxygen-permeable contact lens that rests on the sclera and creates a tear-filled vault over the cornea. The cause of this unique positioning is usually relevant to a specific patient whose cornea is too sensitive to support the lens directly. Scleral lenses may be used to improve vision and reduce pain and light sensitivity for people with disorders or injuries to the eye, such as severe [[dry eye syndrome]] (keratoconjunctivitis sicca), [[microphthalmia]], [[keratoconus]], [[corneal ectasia]], [[Stevens–Johnson syndrome]], [[Sjögren's syndrome]], [[aniridia]], neurotrophic keratitis (anesthetic corneas), complications post-LASIK, high order [[aberrations of the eye]], complications post-corneal transplant and [[Pellucid marginal degeneration|pellucid degeneration]]. Injuries to the eye such as surgical complications, distorted corneal implants, as well as chemical and burn injuries also may be treated with scleral lenses.<ref>{{Cite journal |last=Caceres |first=Vanessa |date=June 2009 |title=Taking a second look at scleral lenses |url=http://www.eyeworld.org/article-taking-a-second-look-at-scleral-lenses |url-status=dead |journal=ASCRS EyeWorld |archive-url=https://web.archive.org/web/20190228004334/https://www.eyeworld.org/article-taking-a-second-look-at-scleral-lenses |archive-date=28 February 2019 |access-date=18 May 2014}}</ref>

====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<ref>{{Cite journal |last=Alvarez-Lorenzo |first=Carmen |last2=Anguiano-Igea |first2=Soledad |last3=Varela-García |first3=Angela |last4=Vivero-Lopez |first4=María |last5=Concheiro |first5=Angel |date=January 2019 |title=Bioinspired hydrogels for drug-eluting contact lenses |journal=Acta Biomaterialia |volume=84 |pages=49–62 |doi=10.1016/j.actbio.2018.11.020 |pmid=30448434 |s2cid=53780024}}</ref> while protecting an injured or diseased cornea<ref>{{Cite journal |last=Zidan |first=Ghada |last2=Rupenthal |first2=Ilva D. |last3=Greene |first3=Carol |last4=Seyfoddin |first4=Ali |date=2018 |title=Medicated ocular bandages and corneal health: potential excipients and active pharmaceutical ingredients |journal=Pharmaceutical Development and Technology |volume=23 |issue=3 |pages=255–260 |doi=10.1080/10837450.2017.1377232 |pmid=28875742 |s2cid=32765975}}</ref> from the constant rubbing of blinking eyelids, thereby allowing it to heal.<ref>{{Cite web |title=Eye Health Guide – Eye Diseases, Eye Problems and Eye Conditions |url=http://eyemdlink.com/terminology/bandage_contact_lens.htm |url-status=dead |archive-url=https://web.archive.org/web/20080409214021/http://eyemdlink.com/terminology/bandage_contact_lens.htm |archive-date=9 April 2008 |access-date=26 March 2015 |website=All About Vision}}</ref> They are used in the treatment of conditions including [[bullous keratopathy]], [[Keratoconjunctivitis sicca|dry eyes]], [[corneal abrasion]]s and [[recurrent corneal erosion|erosion]], [[keratitis]], corneal [[edema]], [[descemetocele]], [[corneal ectasia]], [[Mooren's ulcer]], anterior corneal dystrophy, and neurotrophic keratoconjunctivitis.<ref>{{Cite web |title=45 COVERAGE ISSUES – SUPPLIES – DRUGS 11–91 45 |url=http://new.cms.hhs.gov/manuals/downloads/Pub06_PART_45.pdf |url-status=dead |archive-url=https://web.archive.org/web/20060304101146/http://new.cms.hhs.gov/manuals/downloads/Pub06_PART_45.pdf |archive-date=4 March 2006 |access-date=1 March 2006 |publisher=[[Centers for Medicare and Medicaid Services]] |df=dmy-all}}</ref> Contact lenses that deliver drugs to the eye have also been developed.<ref>{{Cite web |title=Qmed is the world's only directory of pre-qualified suppliers to the medical device and in vitro diagnostics industry. - Qmed |url=http://www.devicelink.com/mddi/archive/05/01/011.html |url-status=dead |archive-url=https://web.archive.org/web/20081205140248/http://www.devicelink.com/mddi/archive/05/01/011.html |archive-date=5 December 2008 |access-date=26 March 2015}}</ref>

===Materials===
[[File:Eye with contact lens.jpg|thumb|alt=Closeup of the eye, showing the light tint on the rim of a corrective contact lense|Non-cosmetic contact lenses become almost invisible once inserted in the eye. Most corrective contact lenses come with a light "handling tint" that renders it slightly more visible on the eye, sometimes visible against the [[sclera]].]]

====Rigid lenses====
Glass lenses were never comfortable enough to gain widespread popularity. The first lenses to do so were those made from [[polymethyl methacrylate]] (PMMA or Perspex/Plexiglas), now commonly referred to as "hard" lenses. Their main disadvantage is they do not allow [[oxygen]] to pass through to the [[cornea]], which can cause a number of adverse, and often serious, clinical events. Starting in the late 1970s, improved rigid materials which were [[Oxygen permeability|oxygen-permeable]] were developed. Contact lenses made from these materials are called [[rigid gas permeable]] lenses (RGPs).

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 [[Post-LASIK ectasia|ectasias]]. In most cases, patients with keratoconus see better through rigid lenses than through [[eyeglasses|glasses]]. Rigid lenses are more chemically inert, allowing them to be worn in more challenging environments where chemical inertia is important compared to soft lenses.<ref>{{Cite web |title=Rigid contact lenses |url=http://www.eagleeyeuk.com/rigid-contact-lenses/ |access-date=2022-04-28 |website=Eagle Eyes UK |language=en-US}}</ref>

====Soft lenses====
{{see also|List of soft contact lens materials}}
Soft lenses are more flexible than rigid lenses and can be gently rolled or folded without damaging the lens. While rigid lenses require a period of adaptation before comfort is achieved, new soft lens wearers typically report lens awareness rather than pain or discomfort.

Hydrogel lenses rely on their water content to transmit oxygen through the lens to the cornea. As a result, higher water content lenses allowed more oxygen to the cornea. In 1998, [[silicone hydrogel]], or Si-hy lenses became available. These materials have both the extremely high [[oxygen permeability]] of [[silicone]] and the comfort and clinical performance of the conventional hydrogels. Because silicone allows more oxygen permeability than water, oxygen permeability of silicone hydrogels is not tied to the lenses' water content. Lenses have now been developed with so much oxygen permeability that they are approved for overnight wear (extended wear). Lenses approved for daily wear are also available in silicone hydrogel materials.<ref>FDA Premarket Notification for [http://acuvue-now.com/latest-news/news-flash/121-green-light-for-1-day-acuvue-trueye.html "new silicone hydrogel lens for daily wear"] {{webarchive|url=https://web.archive.org/web/20081003075751/http://acuvue-now.com/latest-news/news-flash/121-green-light-for-1-day-acuvue-trueye.html |date=3 October 2008 }} 'July 2008.</ref>

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. When comparing traditional hydrogel soft lens contacts with silicone hydrogel versions, there is no clear evidence to recommend a superior lens.<ref>{{Cite journal |last=Haworth |first=Kristina |last2=Travis |first2=Darian |last3=Leslie |first3=Louis |last4=Fuller |first4=Daniel |last5=Pucker |first5=Andrew D |date=2023-09-19 |editor-last=Cochrane Eyes and Vision Group |title=Silicone hydrogel versus hydrogel soft contact lenses for differences in patient-reported eye comfort and safety |journal=Cochrane Database of Systematic Reviews |language=en |volume=2023 |issue=9 |pages=CD014791 |doi=10.1002/14651858.CD014791.pub2 |pmc=10507745 |pmid=37724689}}</ref>

Disadvantages of silicone hydrogels are that they are slightly stiffer and the lens surface can be hydrophobic, thus less "wettable" – factors that can influence comfort of lens use. New manufacturing techniques and changes to multipurpose solutions have minimized these effects. Those new techniques are often broken down into 3 generations:<ref name="szcz">{{Cite web |last=Szczotka-Flynn |first=Loretta |date=1 May 2008 |title=Looking at Silicone Hydrogels Across Generations |url=http://www.optometricmanagement.com/articleviewer.aspx?articleid=101727 |url-status=live |archive-url=https://web.archive.org/web/20110719173206/http://www.optometric.com/article.aspx?article=101727 |archive-date=19 July 2011 |access-date=5 October 2021 |website=www.optometricmanagement.com}}</ref><ref name="chou">{{Cite web |last=Chou |first=Brian |date=1 June 2008 |title=The Evolution of Silicone Hydrogel Lenses |url=https://www.clspectrum.com/issues/2008/june-2008/the-evolution-of-silicone-hydrogel-lenses |url-status=live |archive-url=https://web.archive.org/web/20161230160857/https://www.clspectrum.com/issues/2008/june-2008/the-evolution-of-silicone-hydrogel-lenses |archive-date=30 December 2016 |access-date=5 October 2021 |website=www.clspectrum.com}}</ref>

* 1st generation (plasma coating): A surface modification process called plasma coating alters the lens surface's hydrophobic nature;
* 2nd generation (wetting agents): Another technique incorporates internal rewetting agents to make the lens surface hydrophilic;
* 3rd generation (inherently wettable): A third process uses longer backbone polymer chains that results in less cross linking and increased wetting without surface alterations or additive agents.

====Hybrid====
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.<ref>{{Cite web |last=White |first=Neal |last2=Jennings |first2=Christopher |last3=Pelka |first3=Kevin |date=16 January 2015 |title=Hybrid contact lens |url=https://patents.google.com/patent/US9625738B2/en |access-date=28 February 2018}}</ref>

===Wear schedule===
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.<ref>{{Cite web |title=Contact Lens Types |url=https://www.aao.org/eye-health/glasses-contacts/contact-lens-types |access-date=30 April 2020 |website=American Academy of Ophthalmology}}</ref> 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.

Wearing lenses designed for daily wear overnight has an increased risk for corneal infections, corneal ulcers and [[corneal neovascularization]]—this latter condition, once it sets in, cannot be reversed and will eventually spoil vision acuity through diminishing corneal transparency. The most common complication of extended wear is giant papillary conjunctivitis (GPC), sometimes associated with a poorly fitting contact lens.

===Replacement schedule===
Contact lenses are often categorized by their replacement schedule. Single use lenses (called 1-day or daily disposables) are discarded after one use. Because they do not have to stand up to the wear and tear of repeated uses, these lenses can be made thinner and lighter, greatly improving their comfort. Lenses replaced frequently gather fewer deposits of [[allergens]] and [[pathogen|germs]], making these lenses preferable for patients with ocular [[allergies]] or for those who are prone to infection. Single-use lenses are also useful for people who wear contact lenses infrequently, or when losing a lens is likely or not easily replaced (such as when on vacation). They are also considered useful for children because cleaning or disinfecting is not needed, leading to improved compliance.

Other disposable contact lenses are designed for replacement every two or four weeks. Quarterly or annual lenses, which used to be very common, are now much less so. Rigid gas permeable lenses are very durable and may last for several years without the need for replacement. PMMA hards were very durable and were commonly worn for 5 to 10 years but had several drawbacks.

Lenses with different replacement schedules can be made of the same material. Although the materials are alike, differences in the manufacturing processes determine if the resulting lens will be a "daily disposable" or one recommended for two- or four-week replacement. However, sometimes manufacturers use absolutely identical lenses and just repackage them with different labels.<ref>{{Cite news |date=1993-07-12 |title=The Only Difference Is When You Throw Them Away |url=https://www.bloomberg.com/news/articles/1993-07-11/the-only-difference-is-when-you-throw-them-away |access-date=2016-12-26 |work=Bloomberg.com}}</ref><ref>{{Cite web |title=Contact Lenses – Types of Contact Lenses. Disposable (Replacement Schedule) Contact Lenses |url=https://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/HomeHealthandConsumer/ConsumerProducts/ContactLenses/ucm062319.htm#dcl |access-date=2016-12-26 |website=www.fda.gov |language=en}}</ref>