Editing Amblyopia

{{short description|Failure of the brain to process input from one eye}}
{{Use dmy dates|date=June 2024}}
{{Infobox medical condition (new)
| name            = Amblyopia
| synonyms        = Lazy eye<ref name=NEI2013/>
| image           = Child eyepatch.jpg
| caption         = A child wearing an adhesive eyepatch to correct amblyopia
| field           = [[Ophthalmology]], [[optometry]]
| pronounce       = {{IPAc-en|ˌ|æ|m|b|l|i|ˈ|oʊ|p|i|.|ə}} {{respell|AM|blee|OH|pee|ə}}
| symptoms        = [[Decreased vision]]
| complications   =
| onset           = Before age five<ref name=BMJ2015/>
| duration        =
| types           =
| causes          = [[strabismus|Poor alignment of the eyes]], eye [[astigmatism|being irregularly shaped such that focusing is difficult]], one eye [[anisometropia|being more nearsighted or farsighted]], [[cataract|clouding of the lens]]<ref name=NEI2013/>
| risks           =
| diagnosis       = [[eye examination|Vision testing]]<ref name=NEI2013/>
| differential    = [[Brainstem]] disorders, [[optic nerve]] disorder, [[eye disease]]s<ref>{{cite book |last1=Ferri |first1=Fred F. | name-list-style = vanc | title = Ferri's differential diagnosis: a practical guide to the differential diagnosis of symptoms, signs, and clinical disorders |date=2010 |publisher=Elsevier/Mosby |location=Philadelphia, PA |isbn=978-0-323-07699-9 |page=Chapter A |edition=2nd}}</ref>
|prevention      =
|treatment       = [[Glasses]], [[eyepatch]]<ref name=NEI2013/><ref name=BMJ2015/><ref name=Mac2015/>
| medication      =
| prognosis       =
| frequency       = ~2% of adults<ref name=Web2005/>
| deaths          =
}}
<!-- Definition and symptoms -->
'''Amblyopia''', also called '''lazy eye''', is a disorder of sight in which the brain fails to fully process input from one eye and over time favors the other eye.<ref name=NEI2013/><!-- Quote = It develops when there's a breakdown in the way the brain and the eye work together, and the brain cannot recognize the sight from one eye. Over time, the brain relies more and more on the other, stronger eye  --> It results in decreased vision in an eye that typically appears normal in other aspects.<ref name=NEI2013/> Amblyopia is the most common cause of decreased vision in a single eye among children and younger adults.<ref name=NEI2013>{{cite web |title=Facts About Amblyopia |url=https://nei.nih.gov/health/amblyopia/amblyopia_guide |website=National Eye Institute |access-date=27 July 2016 |date=September 2013 |url-status = live |archive-url=https://web.archive.org/web/20160727233820/https://nei.nih.gov/health/amblyopia/amblyopia_guide |archive-date=27 July 2016}}</ref>

<!-- Cause and diagnosis -->
The cause of amblyopia can be any condition that interferes with focusing during early childhood.<ref name=NEI2013/><ref name=Sch2002>{{cite book |last1=Schwartz |first1=M. William | name-list-style = vanc |title=The 5-minute pediatric consult |date=2002 |publisher=Lippincott Williams & Wilkins |location=Philadelphia |isbn=978-0-7817-3539-1 |page=110 |edition=3rd |url=https://books.google.com/books?id=SRi0WnNisW8C&pg=PA110 }}</ref> This can occur from [[strabismus|poor alignment of the eyes]] (strabismic), an eye [[astigmatism|being irregularly shaped]] such that focusing is difficult, one eye [[anisometropia|being more nearsighted or farsighted]] than the other (refractive), or [[cataract|clouding of the lens]] of an eye (deprivational).<ref name=NEI2013/> After the underlying cause is addressed, vision is not restored right away, as the mechanism also involves the brain.<ref name=Sch2002/><ref name=Levi2013>{{cite journal |vauthors = Levi DM |title = Linking assumptions in amblyopia |journal = Visual Neuroscience |volume = 30 |issue = 5–6 |pages = 277–87|date = November 2013 |pmid = 23879956 |pmc = 5533593 |doi = 10.1017/S0952523813000023 }}</ref> Amblyopia can be difficult to detect, so [[eye examination|vision testing]] is recommended for all children around the ages of four to five.<ref name=BMJ2015>{{cite journal |vauthors = Jefferis JM, Connor AJ, Clarke MP |title = Amblyopia |journal = BMJ |volume = 351 |pages = h5811 |date = November 2015 |pmid = 26563241 |doi = 10.1136/bmj.h5811 |s2cid = 220101666}}</ref>

<!-- Treatment and prognosis -->
Early detection improves treatment success.<ref name=BMJ2015/> [[Eye glasses|Glasses]] may be all the treatment needed for some children.<ref name=BMJ2015/><ref name=Mac2015>{{cite journal |vauthors = Maconachie GD, Gottlob I |title = The challenges of amblyopia treatment |journal = Biomedical Journal |volume = 38 |issue = 6 | pages = 510–6 | date = December 2015 |pmid = 27013450 |pmc = 6138377 |doi = 10.1016/j.bj.2015.06.001 }}</ref> If this is not sufficient, treatments which encourage or force the child to use the weaker eye are used.<ref name=NEI2013/> This is done by either using a [[eyepatch|patch]] or putting [[atropine]] in the stronger eye.<ref name=NEI2013/><ref name="National Eye Institute 2019">{{cite web |title=Amblyopia (Lazy Eye) |website=National Eye Institute |date=2019-07-02 |url=https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/amblyopia-lazy-eye |access-date=2020-01-31 |quote=Putting special eye drops in the stronger eye. A once-a-day drop of the drug atropine can temporarily blur near vision, which forces the brain to use the other eye. For some kids, this treatment works as well as an eye patch, and some parents find it easier to use (for example, because young children may try to pull off eye patches).}}</ref> Without treatment, amblyopia typically persists.<ref name=NEI2013/> Treatment in adulthood is usually much less effective.<ref name=NEI2013/>

<!-- Epidemiology and prognosis -->
Amblyopia begins by the age of five.<ref name=BMJ2015/> In adults, the disorder is estimated to affect 1–5% of the population.<ref name=Web2005>{{cite journal |vauthors = Webber AL, Wood J |title = Amblyopia: prevalence, natural history, functional effects and treatment |journal = Clinical & Experimental Optometry |volume = 88 |issue = 6 |pages = 365–75 |date = November 2005 |pmid = 16329744 |doi = 10.1111/j.1444-0938.2005.tb05102.x |s2cid = 39141527 |doi-access = free }}</ref> While treatment improves vision, it does not typically restore it to normal in the affected eye.<ref name=BMJ2015/> Amblyopia was first described in the 1600s.<ref name=Mar2016>{{cite book |veditors = Fazzi E, Bianchi PE |title=Visual Impairments and Developmental Disorders: From diagnosis to rehabilitation Mariani Foundation Paediatric Neurology |date=2016 |publisher=John Libbey Eurotext |isbn=978-2-7420-1482-8 |chapter-url=https://books.google.com/books?id=VVI2DAAAQBAJ&pg=PT26 |vauthors = Bianchi PE, Ricciardelli G, Bianchi A, Arbanini A, Fazzi E |chapter = Chapter 2: Visual Development in Childhood |url-status = live |archive-url=https://web.archive.org/web/20170908154722/https://books.google.com/books?id=VVI2DAAAQBAJ&pg=PT26|page=26 |archive-date=8 September 2017}}</ref> The condition may make people ineligible to be pilots or police officers.<ref name=BMJ2015/> The word ''amblyopia'' is from [[Ancient Greek|Greek]] ἀμβλύς ''amblys'', meaning "blunt", and ὤψ ''ōps'', meaning "sight".<ref>{{cite web |title=Online Etymology Dictionary |url= http://www.etymonline.com/index.php?term=amblyopia |website=etymonline.com |access-date=5 May 2017|url-status = live |archive-url=https://web.archive.org/web/20170908154722/http://www.etymonline.com/index.php?term=amblyopia |archive-date=8 September 2017}}</ref>

==Signs and symptoms==
Many people with amblyopia, especially those who only have a mild form, are not aware they have the condition until tested at older ages, since the vision in their stronger eye is normal. People with amblyopia typically have poor [[stereopsis|stereo vision]], since it requires both eyes. They further may have, on the affected eye, poor pattern recognition, poor [[visual acuity]], and low sensitivity to [[contrast (vision)|contrast]] and [[Motion perception|motion]].<ref name="Hess">{{cite journal | vauthors = Hess RF, Mansouri B, Dakin SC, Allen HA | title = Integration of local motion is normal in amblyopia | journal = Journal of the Optical Society of America A | volume = 23 | issue = 5 | pages = 986–92 | date = May 2006 | pmid = 16642175 | doi = 10.1364/JOSAA.23.000986 | bibcode = 2006JOSAA..23..986H }}</ref>

Amblyopia is characterized by several functional abnormalities in spatial vision, including reductions in [[visual acuity]], [[contrast sensitivity]] function, and [[vernier acuity]], as well as spatial distortion, abnormal spatial interactions, and impaired contour detection. In addition, individuals with amblyopia have binocular abnormalities such as impaired stereoacuity ([[stereoscopic acuity]]) and abnormal [[binocular summation]].<ref name="polat"/> Also, central vision in amblyopes is more [[crowding|crowded]] than central vision in normal observers.<ref name="LeviSong2007">{{cite journal|last1=Levi|first1=Dennis M.|last2=Song|first2=Shuang|last3=Pelli|first3=Denis G.|title=Amblyopic reading is crowded|journal=Journal of Vision|volume=7|issue=2|year=2007|pages=21.1–17|issn=1534-7362|doi=10.1167/7.2.21|pmid=18217836|doi-access=free}}</ref>

These deficits are usually specific to the amblyopic eye. Subclinical deficits of the "better" eye have also been demonstrated.<ref>{{cite journal | vauthors = Simons K | title = Amblyopia characterization, treatment, and prophylaxis | journal = Survey of Ophthalmology | volume = 50 | issue = 2 | pages = 123–66 | year = 2005 | pmid =  15749306| doi = 10.1016/j.survophthal.2004.12.005 }}</ref>

People with amblyopia also have problems of [[binocular vision]] such as limited stereoscopic [[depth perception]] and usually have difficulty seeing the three-dimensional images in hidden stereoscopic displays such as [[autostereogram]]s.<ref name="Tyler">{{Cite book |  vauthors = Tyler CW| year=2004| title= Binocular Vision In, Duane's Foundations of Clinical Ophthalmology | volume = 2 | veditors = Tasman W, Jaeger EA | publisher = J.B. Lippincott Co. | location = Philadelphia }}</ref> Perception of depth, from monocular cues such as size, [[Perspective (visual)|perspective]], and [[Parallax|motion parallax]] remains normal.

==Cause==
Amblyopia, often referred to as "lazy eye," can be categorized into three types:

# '''Deprivation Amblyopia''': This occurs when something obstructs light from entering the eye, preventing proper vision development. A congenital cataract is an example of such a condition.
# '''Strabismic Amblyopia''': The most common form, this type arises when the eyes are not properly aligned, leading to double vision. To avoid confusion, the brain compensates by ignoring the visual input from the misaligned eye.
# '''Refractive Amblyopia''': This type is caused by a significant difference in uncorrected refractive errors, such as nearsightedness or farsightedness, between the two eyes.

===Strabismus===
{{Further|Strabismus}}
Strabismus, sometimes also incorrectly called lazy eye, is a condition in which the eyes are misaligned.<ref name=handbook>{{cite book|title=Handbook of Pediatric Strabismus and Amblyopia | last1 = Wright | first1 = Kenneth W. | last2 = Spiegel | first2 = Peter H. | last3 = Thompson | first3 = Lisa S. | name-list-style = vanc |year=2006|isbn=978-0-387-27924-4|publisher=[[Springer Science+Business Media|Springer]]|location=New York, New York}}</ref> Strabismus usually results in normal vision in the preferred sighting (or "fellow") eye (the eye that the person prefers to use), but may cause abnormal vision in the deviating or strabismic eye due to the difference between the images projecting to the brain from the two eyes.<ref>{{cite journal | vauthors = Levi DM | title = Visual processing in amblyopia: human studies | journal = Strabismus | volume = 14 | issue = 1 | pages = 11–9 | date = March 2006 | pmid = 16513566 | doi = 10.1080/09273970500536243 | s2cid = 29190763 }}</ref>
Adult-onset strabismus usually causes double vision ([[diplopia]]), since the two eyes are not fixed on the same object.
Children's brains are more [[Neuroplasticity|neuroplastic]], so can more easily adapt by [[Suppression (eye)|suppressing images]] from one of the eyes, eliminating the double vision. This plastic response of the brain interrupts the brain's normal development, resulting in the amblyopia.{{citation needed|date=July 2018}} Recent evidence points to a cause of infantile strabismus lying with the input to the [[visual cortex]].<ref>{{cite journal | vauthors = Tychsen L | title = The cause of infantile strabismus lies upstairs in the cerebral cortex, not downstairs in the brainstem | journal = Archives of Ophthalmology | volume = 130 | issue = 8 | pages = 1060–1 | date = August 2012 | pmid = 22893080 | doi = 10.1001/archophthalmol.2012.1481 }}</ref>

Those with strabismic amblyopia tend to show ocular motion deficits when reading, even when they use the nonamblyopic eye. In particular, they tend to make more [[saccade]]s per line than persons with normal stereo vision, and to have a reduced [[reading speed]], especially when reading a text with small [[font size]].<ref name="pmid24370829">{{cite journal | vauthors = Kanonidou E, Gottlob I, Proudlock FA | title = The effect of font size on reading performance in strabismic amblyopia: an eye movement investigation | journal = Investigative Ophthalmology & Visual Science | volume = 55 | issue = 1 | pages = 451–9 | date = January 2014 | pmid = 24370829 | doi = 10.1167/iovs.13-13257 | doi-access = free | hdl = 2381/38991 | hdl-access = free }}</ref><ref name="pmid20207968">{{cite journal | vauthors = Kanonidou E, Proudlock FA, Gottlob I | title = Reading strategies in mild to moderate strabismic amblyopia: an eye movement investigation | journal = Investigative Ophthalmology & Visual Science | volume = 51 | issue = 7 | pages = 3502–8 | date = July 2010 | pmid = 20207968 | doi = 10.1167/iovs.09-4236 | doi-access =  }}</ref>{{primary source inline|date=February 2019}}

Strabismic amblyopia is treated by clarifying the visual image with glasses, or encouraging use of the amblyopic eye with an [[eyepatch]] over the dominant eye or [[Atropine#Ophthalmic use|pharmacologic penalization]] of the better eye. Penalization usually consists of applying [[atropine]] drops to temporarily paralyze the accommodation reflex, leading to the blurring of vision in the good eye. It also dilates the [[pupil]]. This helps to prevent the bullying and teasing associated with wearing a patch, although sometimes application of the eye drops is challenging. The ocular alignment itself may be treated with surgical or nonsurgical methods, depending on the type and severity of the strabismus.<ref name="Holmes">{{cite journal | vauthors = Holmes JM, Repka MX, Kraker RT, Clarke MP | title = The treatment of amblyopia | journal = Strabismus | volume = 14 | issue = 1 | pages = 37–42 | date = March 2006 | pmid = 16513568 | doi = 10.1080/09273970500536227 | s2cid = 31165871 }}</ref>

===Refractive===
Refractive amblyopia may result from [[anisometropia]] (unequal refractive error between the two eyes).<ref>{{cite journal | first1 = Robert F.| last1 = Rutstein | first2 = David | last2 = Corliss | name-list-style = vanc |title=Relationship between Anisometropia, Amblyopia, and Binocularity|journal=Optometry & Vision Science|date=April 1999|volume=76|issue=4| pages = 229–33 | doi = 10.1097/00006324-199904000-00026 | pmid = 10333185}}</ref><ref>{{cite journal | vauthors = Weakley DR | title = The association between nonstrabismic anisometropia, amblyopia, and subnormal binocularity | journal = Ophthalmology | volume = 108 | issue = 1 | pages = 163–71 | date = January 2001 | pmid = 11150283 | doi = 10.1016/s0161-6420(00)00425-5 }}</ref> Anisometropia exists when there is a difference in the [[refractive error|power]] between the two eyes. The eye which provides the brain with a clearer image typically becomes the dominant eye. The image in the other eye is blurred, which results in abnormal development of one half of the visual system. Refractive amblyopia is usually less severe than strabismic amblyopia and is commonly missed by [[primary care physician]]s because of its less dramatic appearance and lack of obvious physical manifestation, such as with strabismus.<ref name=AAFP>{{cite journal | vauthors = Simon JW, Kaw P | title = Commonly missed diagnoses in the childhood eye examination | journal = American Family Physician | volume = 64 | issue = 4 | pages = 623–8 | date = August 2001 | pmid = 11529261 | url = http://www.aafp.org/afp/20010815/623.html | access-date = 28 August 2005 | archive-date = 12 September 2005 | archive-url = https://web.archive.org/web/20050912000156/http://www.aafp.org/afp/20010815/623.html | url-status = dead }}</ref> Given that the refractive correction of anisometropia by means of spectacles typically leads to different image magnification for the two eyes, which may in turn prevent binocular vision, a refractive correction using [[contact lens]]es is to be considered. Also [[Refractive surgery#Children|pediatric refractive surgery]] is a treatment option, in particular if conventional approaches have failed due to [[aniseikonia]] or lack of compliance or both.<ref>{{cite journal | vauthors = Astle WF, Rahmat J, Ingram AD, Huang PT | title = Laser-assisted subepithelial keratectomy for anisometropic amblyopia in children: outcomes at 1 year | journal = Journal of Cataract and Refractive Surgery | volume = 33 | issue = 12 | pages = 2028–34 | date = December 2007 | pmid = 18053899 | doi = 10.1016/j.jcrs.2007.07.024 | s2cid = 1886316 }}</ref>

Frequently, amblyopia is associated with a combination of anisometropia and strabismus. In some cases, the vision between the eyes can differ to the point where one eye has twice average vision while the other eye is completely blind.

=== Deprivation and occlusion ===
Deprivation amblyopia (amblyopia ex anopsia) results when the ocular media become [[Opacity (optics)|opaque]], such as is the case with [[congenital cataract]] or [[cornea]]l haziness.<ref name=Angell>{{cite journal | vauthors = Angell LK, Robb RM, Berson FG | title = Visual prognosis in patients with ruptures in Descemet's membrane due to forceps injuries | journal = Archives of Ophthalmology | volume = 99 | issue = 12 | pages = 2137–9 | date = December 1981 | pmid = 7305711 | doi = 10.1001/archopht.1981.03930021013004 }}</ref> These opacities prevent adequate visual input from reaching the eye, and disrupt development. If not treated in a timely fashion, amblyopia may persist even after the cause of the opacity is removed. Sometimes, drooping of the [[eyelid]] ([[ptosis (eyelid)|ptosis]]) or some other problem causes the upper eyelid to physically occlude a child's vision, which may cause amblyopia quickly.  Occlusion amblyopia may be a complication of a [[hemangioma]] that blocks some or all of the eye. Other possible causes of deprivation and occlusion amblyopia include obstruction in the vitreous and [[aphakia]].<ref name=":0">{{Cite journal|last1=Antonio-Santos|first1=Aileen|last2=Vedula|first2=S. Swaroop|last3=Hatt|first3=Sarah R.|last4=Powell|first4=Christine|date=23 March 2020|title=Occlusion for stimulus deprivation amblyopia|journal=The Cochrane Database of Systematic Reviews|volume=3|issue=3 |pages=CD005136|doi=10.1002/14651858.CD005136.pub4|issn=1469-493X|pmc=7089638|pmid=32203629}}</ref> Deprivation amblyopia accounts for less than 3% of all individuals affected by amblyopia.<ref name=":0" />

==Pathophysiology==
Amblyopia is a developmental problem in the brain, not any intrinsic, organic neurological problem in the eyeball (although organic problems can lead to amblyopia which can continue to exist after the organic problem has resolved by medical intervention).<ref name="Mckee">
{{cite journal | vauthors = McKee SP, Levi DM, Movshon JA | title = The pattern of visual deficits in amblyopia | journal = Journal of Vision | volume = 3 | issue = 5 | pages = 380–405 | year = 2003 | pmid = 12875634 | doi = 10.1167/3.5.5 | doi-access = free }}</ref>
The part of the brain receiving images from the affected eye is not stimulated properly and does not develop to its full visual potential. This has been confirmed by direct brain examination. [[David H. Hubel]] and [[Torsten Wiesel]] won the [[Nobel Prize in Physiology or Medicine]] in 1981 for their work in showing the extent of the damage to [[ocular dominance columns]] produced in kittens by sufficient visual deprivation during the so-called "[[critical period]]". The maximum "critical period" in humans is from birth to two years old.<ref name=Cooper>{{Cite web| url=http://www.strabismus.org/detection_diagnosis.html | title=All About Strabismus | first1 = Jeffrey | last1 = Cooper | first2 = Rachel | last2 = Cooper | name-list-style = vanc | publisher=Optometrists Network | access-date=9 March 2008}}</ref>

==Diagnosis==
Amblyopia is diagnosed by identifying low visual acuity in one or both eyes, out of proportion to the structural abnormality of the eye and excluding other visual disorders as causes for the lowered visual acuity. It can be defined as an interocular difference of two lines or more in acuity (e.g. on [[Snellen chart]]) when the eye optics are maximally corrected.<ref name="wright">{{cite book | vauthors =  Wright WK | title = Handbook of Pediatric Strabismus and Amblyopia | url =  https://archive.org/details/handbookpediatri00wrig_371 | url-access =  limited |place = New-York |publisher=Springer |date=2006 |pages=[https://archive.org/details/handbookpediatri00wrig_371/page/n111 103]–137 }}</ref> In young children, visual acuity is difficult to measure and can be estimated by observing the reactions of the patient when one eye is covered, including observing the patient's ability to follow objects with one eye.

Stereotests like the [[Stereopsis#Random dot stereotests|Lang stereotest]] are not reliable exclusion tests for amblyopia. A person who passes the Lang stereotest test is unlikely to have strabismic amblyopia, but could nonetheless have refractive or deprivational amblyopia.<ref name="SchieferWilhelm2007-p16">{{cite book|first1 = Ulrich | last1 = Schiefer | first2 = Helmut | last2 = Wilhelm | first3  =William | last3 = Hart | name-list-style = vanc |title=Clinical Neuro-Ophthalmology: A Practical Guide|url=https://books.google.com/books?id=xMsfcl2YfLoC&pg=PA16|year=2007|publisher=Springer Science & Business Media|isbn=978-3-540-32708-0|page=16|url-status = live|archive-url=https://web.archive.org/web/20170908154722/https://books.google.com/books?id=xMsfcl2YfLoC&pg=PA16|archive-date=8 September 2017}}</ref> Binocular [[retinal birefringence scanning]] may be able to identify, already in very young children, amblyopia that is associated with strabismus, microstrabismus, or reduced fixation accuracy. Diagnosis and treatment of amblyopia as early as possible is necessary to keep the vision loss to a minimum. Screening for amblyopia is recommended in all people between three and five years of age.<ref>{{cite journal | vauthors = Grossman DC, Curry SJ, Owens DK, Barry MJ, Davidson KW, Doubeni CA, Epling JW, Kemper AR, Krist AH, Kurth AE, Landefeld CS, Mangione CM, Phipps MG, Silverstein M, Simon MA, Tseng CW | display-authors = 6 | title = Vision Screening in Children Aged 6 Months to 5 Years: US Preventive Services Task Force Recommendation Statement | journal = JAMA | volume = 318 | issue = 9 | pages = 836–844 | date = September 2017 | pmid = 28873168 | doi = 10.1001/jama.2017.11260 | s2cid = 205084845 }}</ref>

==Treatment==
Treatment of strabismic or anisometropic amblyopia consists of correcting the optical deficit (wearing the necessary spectacle prescription) and often forcing use of the amblyopic eye, by patching the good eye, or instilling [[topical]] [[atropine]] in the good eye, or both.<ref name=handbook/>{{rp|130}}<ref>Coats DK and Paysse EA.  Overview of amblyopia UpToDate.  Last updated: 25 Sep 2014</ref> Atropine appears to result in similar outcomes to patching.<ref>{{Cite journal |date=2019-12-05 |title=A patch or eye drops are similarly effective for the treatment of "lazy eye" in children |url=https://evidence.nihr.ac.uk/alert/a-patch-or-eye-drops-are-similarly-effective-for-the-treatment-of-lazy-eye-in-children |journal=NIHR Evidence |type=Plain English summary |publisher=National Institute for Health and Care Research |doi=10.3310/signal-000849|s2cid=243130859 |url-access=subscription }}</ref><ref>{{cite journal | vauthors = Li T, Qureshi R, Taylor K| title = Conventional occlusion versus pharmacologic penalization for amblyopia | journal = Cochrane Database Syst Rev | volume = 8 | issue = 8 | pages = CD006460 | date = 2019 | pmid = 31461545 | pmc = 6713317 | doi = 10.1002/14651858.CD006460.pub3 }}</ref> If there is overpatching or overpenalizing the good eye when treating amblyopia, "reverse amblyopia" can result.<ref name="Holmes" /><ref name=NEI>[http://www.nei.nih.gov/health/amblyopia/index.asp Amblyopia NEI Health Information] {{webarchive |url=https://web.archive.org/web/20050911041610/http://www.nei.nih.gov/health/amblyopia/index.asp |date=11 September 2005 }}</ref> Eye patching is usually done on a part-time schedule of about 4–6 hours a day. Treatment is continued as long as vision improves. It is not worthwhile continuing to patch for more than 6 months if no improvement continues.<ref name=vaughan>{{cite book| first1 = Emmett T. | last1 = Cunningham | first2 = Paul | last2 = Riordan-Eva | name-list-style = vanc |title=Vaughan & Asbury's general ophthalmology.|publisher=McGraw-Hill Medical|isbn=978-0071634205|edition=18th| date = 2011-05-17 }}</ref>

Deprivation amblyopia is treated by removing the opacity as soon as possible followed by patching or penalizing the good eye to encourage the use of the amblyopic eye.<ref name="Holmes" /> The earlier the treatment is initiated, the easier and faster the treatment is and the less psychologically damaging. Also, the chance of achieving 20/20 vision is greater if treatment is initiated early.<ref>{{cite journal | vauthors = Williams C, Northstone K, Harrad RA, Sparrow JM, Harvey I | title = Amblyopia treatment outcomes after screening before or at age 3 years: follow up from randomised trial | journal = BMJ | volume = 324 | issue = 7353 | page = 1549 | date = June 2002 | pmid = 12089090 | pmc = 116606 | doi = 10.1136/bmj.324.7353.1549 }}</ref>

One of the [[Healthcare in Germany#Public insurance|German public health insurance]] providers, Barmer, has changed its policy to cover, as of 1 April 2014, the cost of software for amblyopic children whose condition did not improve through patching. The app offers dedicated eye exercises that the patient performs while wearing an eyepatch.<ref>{{cite news|url=http://www.aerztezeitung.de/praxis_wirtschaft/telemedizin/article/857948/app-rezept-barmer-bezahlt-internetbasierte-behandlung.html|title=App auf Rezept: Barmer bezahlt internetbasierte Behandlung|trans-title=Prescription app: Barmer pays for internet-based treatment|website=aerztezeitung.de|date=28 March 2014|access-date=29 March 2014|language=de|url-status = live|archive-url=https://web.archive.org/web/20140329174210/http://www.aerztezeitung.de/praxis_wirtschaft/telemedizin/article/857948/app-rezept-barmer-bezahlt-internetbasierte-behandlung.html|archive-date=29 March 2014}}</ref>

Treatment for amblyopia depends on the child’s age, severity of the vision loss and the prescribing doctor’s preference. Treatment options include, vision therapy, total or partial occlusion therapy, prescription eyeglasses or any combination. Common types of occlusion therapy include the use of eye-patches or optical blurring. Optical blurring can include the use of pharmacological agents (eye drops) or visual degradation using either power to blur the image or foils placed over the lens.<ref>{{Cite web |title=Common Kid's Eye Conditions |url=https://www.2020mag.com/article/common-kid39s-eye-conditions#:~:text=Hyperopia%E2%80%94The%20normal%20eye%20at,years%20tend%20to%20remain%20hyperopic. |access-date=2024-12-23 |website=www.2020mag.com}}</ref>

Evidence for [[vision therapy]] is unclear as of 2011.<ref>{{cite journal |last1=West |first1=S |last2=Williams |first2=C |title=Amblyopia. |journal=BMJ Clinical Evidence |date=30 June 2011 |volume=2011 |pmid=21714945|pmc=3275294 }}</ref>

===Older age===
Treatment of individuals age 9 through to adulthood is possible through applied [[perceptual learning]].<ref name="polat">{{cite journal | vauthors = Polat U, Ma-Naim T, Belkin M, Sagi D | title = Improving vision in adult amblyopia by perceptual learning | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 101 | issue = 17 | pages = 6692–7 | date = April 2004 | pmid = 15096608 | pmc = 404107 | doi = 10.1073/pnas.0401200101 | bibcode = 2004PNAS..101.6692P | doi-access = free }}</ref><ref name=zhou>{{cite journal | vauthors = Zhou Y, Huang C, Xu P, Tao L, Qiu Z, Li X, Lu ZL | title = Perceptual learning improves contrast sensitivity and visual acuity in adults with anisometropic amblyopia | journal = Vision Research | volume = 46 | issue = 5 | pages = 739–50 | date = March 2006 | pmid = 16153674 | doi = 10.1016/j.visres.2005.07.031 | s2cid = 1290214 | doi-access = free }}</ref><ref>https://pubs.covd.org/VDR/issue8-4/index.html Volume 8, Issue 4, Page 260: Neural Vision Perceptual Learning as an Effective Treatment of Amblyopia</ref><ref name="Effects of Perceptual Learning on D">{{cite journal | pmc=8999262 | date=2022 | last1=Zhong | first1=J. | last2=Wang | first2=W. | last3=Li | first3=J. | last4=Wang | first4=Y. | last5=Hu | first5=X. | last6=Feng | first6=L. | last7=Ye | first7=Q. | last8=Luo | first8=Y. | last9=Zhu | first9=Z. | last10=Li | first10=J. | last11=Yuan | first11=J. | title=Effects of Perceptual Learning on Deprivation Amblyopia in Children with Limbal Dermoid: A Randomized Controlled Trial | journal=Journal of Clinical Medicine | volume=11 | issue=7 | page=1879 | doi=10.3390/jcm11071879 | doi-access=free | pmid=35407483 }}</ref><ref>{{cite journal | pmc=3864996 | date=2013 | last1=Yalcin | first1=E. | last2=Balci | first2=O. | title=Efficacy of perceptual vision therapy in enhancing visual acuity and contrast sensitivity function in adult hypermetropic anisometropic amblyopia | journal=Clinical Ophthalmology | volume=8 | pages=49–53 | doi=10.2147/OPTH.S48300 | doi-access=free | pmid=24376340 }}</ref> Tentative evidence shows that perceptual training may be beneficial in adults.<ref>{{cite journal | vauthors = Astle AT, Webb BS, McGraw PV | title = Can perceptual learning be used to treat amblyopia beyond the critical period of visual development? | journal = Ophthalmic & Physiological Optics | volume = 31 | issue = 6 | pages = 564–73 | date = November 2011 | pmid = 21981034 | pmc = 3428831 | doi = 10.1111/j.1475-1313.2011.00873.x }}</ref><ref>{{cite journal | vauthors = Levi DM | title = Prentice award lecture 2011: removing the brakes on plasticity in the amblyopic brain | journal = Optometry and Vision Science | volume = 89 | issue = 6 | pages = 827–38 | date = June 2012 | pmid = 22581119 | pmc = 3369432 | doi = 10.1097/OPX.0b013e318257a187 }}</ref>

==Epidemiology==
Amblyopia occurs in 2–5% of the population in Western countries.{{Which|date=August 2019}}<ref name="wright"/><ref>{{cite journal | vauthors = Elflein HM, Fresenius S, Lamparter J, Pitz S, Pfeiffer N, Binder H, Wild P, Mirshahi A | title = The prevalence of amblyopia in Germany: data from the prospective, population-based Gutenberg Health Study | journal = Deutsches Ärzteblatt International | volume = 112 | issue = 19 | pages = 338–44 | date = May 2015 | pmid = 26043421 | pmc = 4458790 | doi = 10.3238/arztebl.2015.0338 }}</ref> In the UK, 90% of visual health appointments in the child concern amblyopia.<ref>{{cite journal | vauthors = Stewart CE, Fielder AR, Stephens DA, Moseley MJ | title = Design of the Monitored Occlusion Treatment of Amblyopia Study (MOTAS) | journal = The British Journal of Ophthalmology | volume = 86 | issue = 8 | pages = 915–9 | date = August 2002 | pmid = 12140215 | pmc = 1771248 | doi = 10.1136/bjo.86.8.915 }}</ref>

Depending on the chosen criterion for diagnosis, 1–4% of the children have amblyopia.<ref>{{cite journal | vauthors = Birch EE | title = Amblyopia and binocular vision | journal = Progress in Retinal and Eye Research | volume = 33 | pages = 67–84 | date = March 2013 | pmid = 23201436 | pmc = 3577063 | doi = 10.1016/j.preteyeres.2012.11.001 }}</ref>

==Research==
A 2009 study,<ref name=Thompson>{{cite journal | vauthors = Thompson B, Mansouri B, Koski L, Hess RF | title = Brain plasticity in the adult: modulation of function in amblyopia with rTMS | journal = Current Biology | volume = 18 | issue = 14 | pages = 1067–71 | date = July 2008 | pmid = 18635353 | doi = 10.1016/j.cub.2008.06.052 | s2cid = 14808576 | doi-access =  | bibcode = 2008CBio...18.1067T }}</ref> widely reported in the popular press,<ref name=rTMS>{{Cite news | first = Andread | last = Seabrook | name-list-style = vanc | url=https://www.npr.org/templates/story/story.php?storyId=92965339 | title=Magnetic Pulses To Brain Help 'Lazy Eye' | publisher = NPR |url-status = live| archive-url=https://web.archive.org/web/20090108161749/http://www.npr.org/templates/story/story.php?storyId=92965339 | archive-date=8 January 2009 }}</ref> suggested that repetitive [[transcranial magnetic stimulation]] may temporarily improve contrast sensitivity and spatial resolution in the affected eye of adults with amblyopia. This approach is still under development,<ref>{{cite journal | vauthors = Hess RF, Thompson B | title = New insights into amblyopia: binocular therapy and noninvasive brain stimulation | journal = Journal of AAPOS | volume = 17 | issue = 1 | pages = 89–93 | date = February 2013 | pmid = 23352385 | doi = 10.1016/j.jaapos.2012.10.018 }}</ref> and the results await verification by other researchers. Comparable results may be achieved using different types of brain stimulation,<ref name="Hess, Robert F. 2014">{{cite journal | vauthors = Hess RF, Thompson B, Baker DH | title = Binocular vision in amblyopia: structure, suppression and plasticity | journal = Ophthalmic & Physiological Optics | volume = 34 | issue = 2 | pages = 146–62 | date = March 2014 | pmid = 24588532 | doi = 10.1111/opo.12123 | s2cid = 22584125 | url = http://eprints.whiterose.ac.uk/103305/1/s1_ln15735138_245425685_1939656818Hwf325794455IdV_171171828415735138PDF_HI0001.pdf | doi-access = free }}</ref> such as anodal [[transcranial direct current stimulation]]<ref>{{cite journal | vauthors = Spiegel DP, Byblow WD, Hess RF, Thompson B | title = Anodal transcranial direct current stimulation transiently improves contrast sensitivity and normalizes visual cortex activation in individuals with amblyopia | journal = Neurorehabilitation and Neural Repair | volume = 27 | issue = 8 | pages = 760–9 | date = October 2013 | pmid = 23774122 | doi = 10.1177/1545968313491006 | s2cid = 38437179 }}</ref> and theta burst [[rTMS]].<ref>{{cite journal | vauthors = Clavagnier S, Thompson B, Hess RF | title = Long lasting effects of daily theta burst rTMS sessions in the human amblyopic cortex | journal = Brain Stimulation | volume = 6 | issue = 6 | pages = 860–7 | date = November 2013 | pmid = 23664756 | doi = 10.1016/j.brs.2013.04.002 | s2cid = 36592293 }}</ref>

A 2013 study concluded that converging evidence indicates decorrelated binocular experience plays a pivotal role in the genesis of amblyopia and the associated residual deficits.<ref name="Birch2013">{{cite journal | vauthors = Birch EE | title = Amblyopia and binocular vision | journal = Progress in Retinal and Eye Research | volume = 33 | pages = 67–84 | date = March 2013 | pmid = 23201436 | pmc = 3577063 | doi = 10.1016/j.preteyeres.2012.11.001 | type = Review }}</ref> Another study of 2013<ref name=Li>{{cite journal | vauthors = Li J, Thompson B, Deng D, Chan LY, Yu M, Hess RF | title = Dichoptic training enables the adult amblyopic brain to learn | journal = Current Biology | volume = 23 | issue = 8 | pages = R308-9 | date = April 2013 | pmid = 23618662 | doi = 10.1016/j.cub.2013.01.059 | doi-access = free | bibcode = 2013CBio...23.R308L }}</ref> suggests that playing a version of the popular game [[Tetris]] that is modified such that each eye sees separate components of the game may also help to treat this condition in adults.<ref>{{cite web | first = Joseph | last = Nordqvist | name-list-style = vanc | url = http://www.medicalnewstoday.com/articles/259547.php | title = Tetris Video Game Helps Treat Lazy Eye | archive-url = https://web.archive.org/web/20130529010856/http://www.medicalnewstoday.com/articles/259547.php | archive-date=29 May 2013 | work = Medical News Today (MNT) | date = 23 April 2013 }}</ref> Furthermore, the effects of this kind of therapy may be further enhanced by noninvasive brain stimulation<ref name="Hess, Robert F. 2014"/> as shown by a recent study using anodal [[Transcranial direct-current stimulation|tDCS]].<ref>{{cite journal | vauthors = Spiegel DP, Li J, Hess RF, Byblow WD, Deng D, Yu M, Thompson B | title = Transcranial direct current stimulation enhances recovery of stereopsis in adults with amblyopia | journal = Neurotherapeutics | volume = 10 | issue = 4 | pages = 831–9 | date = October 2013 | pmid = 23857313 | pmc = 3805870 | doi = 10.1007/s13311-013-0200-y }}</ref>

A 2014 Cochrane review sought to determine the effectiveness of occlusion treatment on patients with sensory deprivation amblyopia, but no trials were found eligible to be included in the review.<ref name=":0" /> However, good outcomes from occlusion treatment for sensory deprivation amblyopia likely rely on compliance with the treatment.

==See also==
*[[Functional visual loss]]

== References ==
{{Reflist}}

== Further reading ==
{{refbegin}}
* {{cite journal | vauthors = Birch EE | title = Amblyopia and binocular vision | journal = Progress in Retinal and Eye Research | volume = 33 | pages = 67–84 | date = March 2013 | pmid = 23201436 | pmc = 3577063 | doi = 10.1016/j.preteyeres.2012.11.001 | type = review }}
* {{cite book|last1=Daw|first1=Nigel W.|title=Visual Development|edition=Third|year=2014|publisher=Springer|isbn=978-1461490586}}
:* Chapter What is Amblyopia? pp.&nbsp;123–145, {{doi|10.1007/978-1-4614-9059-3_8}},
:* Chapter Treatment of Amblyopia pp.&nbsp;167–180, {{doi|10.1007/978-1-4614-9059-3_10}}.
* {{cite journal | vauthors = Stewart CE, Moseley MJ, Fielder AR | title = Amblyopia therapy: an update | journal = Strabismus | volume = 19 | issue = 3 | pages = 91–8 | date = September 2011 | pmid = 21870912 | doi = 10.3109/09273972.2011.600421 | s2cid = 38988992 }}
* {{cite journal | vauthors = Sengpiel F | title = Plasticity of the visual cortex and treatment of amblyopia | journal = Current Biology | volume = 24 | issue = 18 | pages = R936–R940 | date = September 2014 | pmid = 25247373 | doi = 10.1016/j.cub.2014.05.063 | type = review | doi-access = free | bibcode = 2014CBio...24.R936S }}
* {{cite journal | vauthors = Hamm LM, Black J, Dai S, Thompson B | title = Global processing in amblyopia: a review | journal = Frontiers in Psychology | volume = 5 | page = 583 | year = 2014 | pmid = 24987383 | pmc = 4060804 | doi = 10.3389/fpsyg.2014.00583 | type = review | doi-access = free }}
{{refend}}

== External links ==
{{Medical resources
|   DiseasesDB     = 503
|   ICD10          = {{ICD10|H|53|0|h|53}}
|   ICD9           = {{ICD9|368.0}}
|   ICDO           =
|   OMIM           =
|   MedlinePlus    = 001014
|   eMedicineSubj  = oph
|   eMedicineTopic = 316
|   MeshID         = D000550
}}
{{Commons category|Amblyopia}}
* [https://web.archive.org/web/20050911041610/http://www.nei.nih.gov/health/amblyopia/index.asp National Eye Institute (NEI)] Resource Guide
* [https://web.archive.org/web/20070601225119/http://www.lazyeyesite.org/ Lazy Eye Site] from the [[National Health Service]], [[UK]]
* [https://lookafteryoureyes.org/eye-conditions/lazy-eye/ Look After Your Eyes - patient information on Amblyopia or 'lazy eye'] by [[College of Optometrists]]
{{Eye pathology}}

{{Authority control}}

[[Category:Visual disturbances and blindness]]
[[Category:Wikipedia medicine articles ready to translate]]
[[Category:Wikipedia neurology articles ready to translate]]