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| The [[eye]], like any other optical system, suffers from a number of specific [[optical aberrations]]. The optical quality of the eye is limited by optical aberrations, [[diffraction]] and [[Light scattering|scatter]].<ref name=cervino>{{cite journal|last=Cerviño|first=A|coauthors=Hosking, SL; Montes-Mico, R; Bates, K|title=Clinical ocular wavefront analyzers.|journal=Journal of refractive surgery (Thorofare, N.J. : 1995)|date=2007 Jun|volume=23|issue=6|pages=603–16|pmid=17598581}}</ref> Correction of spherocylindrical [[refractive error]]s has been possible for nearly two centuries following Airy's development of method's to measure and correct ocular astigmatism. It has only recently become possible to measure the '''aberrations of the eye''' and with the advent of [[refractive surgery]] it might be possible to correct certain types of irregular astigmatism.
| | As head of Louis Vuitton, Yves Carcelle, who has died at the age of 66, built the French fashion house into one of the world's leading luxury brands.<br>Though it is only one of around 60 such brands owned by LVMH, Louis Vuitton is the conglomerate's driving force, and Carcelle expanded its appeal into areas such as eyewear and jewellery while travelling the world looking for new areas to colonise. One of his key decisions came in 1997 when he hired as creative director the then up-and-coming designer Marc Jacobs, whose introduction of the company's first ready-to-wear line helped seal its place at or near the top of fashion's premier league.<br><br><br>Born in 1948 in Paris, Carcelle graduated in mathematics from the city's �cole Polytechnique then gained a masters in business administration from the business school, Insead. His first job was as a salesman for Spontex a maker of household cleaning products, which he said was excellent training for a career in fashion: "You have to be a good salesmen, if nothing else," he said.<br><br>"And you have to know how to deal with people,"<br>The renowned fashion journalist Suzy Menkes wrote: "My favourite Yves Carcelle story - one he liked to tell with a glass of champagne in hand, perhaps at a private party at home in front of a bold Gilbert & George painting, with his then wife Rebecca at his side and with his boys listening in - was about his early days as a fledgling travelling salesman. Taking to the road with a girlfriend, the young Yves would send her into a hardware store asking with a flirtatious enthusiasm for a new product he was hoping to sell. Ten minutes later, he would be knocking on the same store door, offering to supply the goods. The success was instant."<br><br>Following his stint at Spontex, in 1974 he joined Blenda Pharm laboratories, then five years later was appointed director of the Absorba [http://www.tumblr.com/tagged/clothing+brand clothing brand] at Poron. In 1985 he became president of the textiles firm Descamps, and his success in turning the company around led to his recruitment by Bernard Arnault as LVMH's director of strategy in 1989.<br><br>The following year he became chairman and CEO, then in 1998 head of the LVMH fashion division, which as well as Louis Vuitton includes such brands as Givenchy, Donna Karan, Christian Dior, Celine, Fendi, the jewellers Bulgari and cognac maker Hennessy.<br>Colleagues said [https://Www.Google.com/search?hl=en&gl=us&tbm=nws&q=Carcelle Carcelle] knew little about luxury when he joined Louis Vuitton. But he quickly won Arnault's trust and became one of his most respected lieutenants. "There was a lot of mutual respect between the two men even though they had very different personalities," an LVMH executive.<br><br>"Carcelle was very different from Arnault. Arnault is cold and not really somebody who easily gets excited about something, while Carcelle was very spontaneous and open."<br>Carcelle quadrupled Louis Vuitton's network of stores to just under 470, many of them in strategically important emerging markets such as China. He showed great skill in spreading the Louis Vuitton gospel: a rival told Suzy Menkes how when he and Carcelle would arrive in an often remote Chinese town, Carcelle would hand out beautifully wrapped small leather goods as gifts to the city's mayor and each member of his family.<br><br>In 2001 he went back to his old job following the departure of Marcello Bottoli after only 18 months. "It's not always easy to sum up what our brand means to people, but let me try," he said in 2004. "It's about reliability, quality, style, innovation and authenticity."<br>Carcelle became an expert in easing Louis Vuitton into new markets. When he wasn't globe-trotting, Carcelle was usually in his Paris office by 6am. Though he was softly-spoken, he could raise his voice when necessary - as he did when he let fly at a French government official who went to a Louis Vuitton store opening in Bangkok carrying a fake Vuitton bag.<br><br>Carcelle, who died of renal cancer, stepped down at the end of 2012 as Louis Vuitton's sales growth was starting to slow down after years of double-digit increases. There were calls for a change in management, particularly as Carcelle was in his early 60s. He stayed on as part of the LVMH executive committee and as vice president of the Fondation Louis Vuitton museum, designed by Frank Gehry on the Bois de Boulogne and due to open next month.<br><br>A keen sailor, he was an enthusiastic follower of the Louis Vuitton Cup, which until last year served as the eliminator series for the Americas Cup. Just before the onset of the global financial crisis he was asked if he was worried that his company could suffer.<br>"Not really," he replied. "The great thing about our business is that our customers are very rich - and then they are a bit less rich, but still rich, right?"<br><br>Yves Carcelle, businessman: born Paris 18 May 1948; Chevalier de [http://www.pcs-systems.co.uk/Images/celinebag.aspx http://www.pcs-systems.co.uk/Images/celinebag.aspx] la L�gion d'honneur 2014; twice married (five children); died 31 August 2014. |
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| The appearance of visual complaints such as [[Halo (optical phenomenon)|halos]], [[Glare (vision)|glare]] and [[Diplopia#Monocular|monocular diplopia]] after corneal refractive surgery has long been correlated with the induction of optical aberrations. Several mechanisms may explain the increase in the amount of higher-order aberrations with conventional eximer laser refractive procedures: a change in corneal shape toward oblateness or prolateness (after myopic and hyperopic ablations respectively), insufficient optical zone size and imperfect centration. These adverse effects are particularly noticeable when the pupil is large.<ref name=azar>{{cite book|last=Dimitri T. Azar , Damien Gatinel, Thang Hoang-Xuan|title=Refractive surgery|year=2007|publisher=Mosby Elsevier|location=Philadelphia|isbn=978-0-323-03599-6|edition=2nd ed.}}</ref>
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| ==Wavefront approach to aberrations of the eye==
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| [[File:Diffraction through Pinhole.svg|thumb|130px|right|The flat wavefronts change to spherical wavefronts as they pass through a pinhole]]
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| A wavefront is a surface over which an optical disturbance has a constant phase. Rays and wavefronts are two mutually complementary approaches to light propagation. Wavefronts are always normal (perpendicular) to the rays.
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| For light to converge to a perfect point, the wavefront emerging from the optical system must be a perfect sphere centered on the image point. The distance in micrometers between the actual wavefront and the ideal wavefront is the wavefront aberration, which is the standard method of showing the aberrations of the eye. Therefore, aberrations of the eye are the difference between two surfaces: the ideal and the actual wavefront.
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| == Aberration of normal eyes ==
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| In normal population the dominant aberrations are the ordinary second-order spherocylindrical focus errors which are called [[refractive error]]s. Higher order aberrations are a relatively small component, comprising about 10% of the eye’s total aberrations.<ref name=lawless>{{cite journal|last=Lawless|first=MA|coauthors=Hodge, C|title=Wavefront's role in corneal refractive surgery.|journal=Clinical & experimental ophthalmology|date=2005 Apr|volume=33|issue=2|pages=199–209|pmid=15807834|doi=10.1111/j.1442-9071.2005.00994.x}}</ref>
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| High order aberrations increase with age and mirror symmetry exists between the right and the left eyes.<ref name=Charman />
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| Several studies have reported a compensation of the aberration of the cornea by the aberration of the crystalline lens. The spherical aberration of the cornea is usually positive whereas the young crystalline lens exhibits a negative spherical aberration. Besides, there is strong evidence of compensation for aberrations between the cornea and intraocular optics in cases of astigmatism (horizontal/vertical) and horizontal coma. The balance of corneal and internal aberrations is a typical example of creating two coupling optical systems.<ref name=Lombardo />
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| The accommodative response of the eye results in changes to the lens shape and substantially affects the Wavefront aberration pattern. Most eyes show positive spherical aberration when unaccomodated with a trend toward negative spherical aberration on accommodation.<ref name=cervino />
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| == Low Order Aberrations ==
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| Includes [[Myopia]] (positive defocus), [[hyperopia]] (negative defocus), and [[Astigmatism (eye)|regular astigmatism]]. Other lower-order aberrations are non- visually significant aberrations known as first order aberrations, such as prisms and zero-order aberrations (piston). Low order aberrations account for approximately 90% of the overall wave aberration in the eye.<ref name=Lombardo>{{cite journal|last=Lombardo|first=M|coauthors=Lombardo, G|title=Wave aberration of human eyes and new descriptors of image optical quality and visual performance.|journal=Journal of cataract and refractive surgery|date=2010 Feb|volume=36|issue=2|pages=313–31|pmid=20152616|doi=10.1016/j.jcrs.2009.09.026}}</ref><ref name=ao />
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| == High Order Aberrations ==
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| [[image:Spherical aberration 2.svg|thumb|180px|Spherical aberration. A perfect lens (top) focuses all incoming rays to a point on the Optical axis. In spherical aberration (Bottom) peripheral rays are focused more tightly than central rays.]]
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| There are numerous higher-order aberrations, of which only [[spherical aberration]], [[coma (optics)|coma]] and trefoil are of clinical interest.
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| ''Spherical aberration'' is the cause of night myopia and is commonly increased after myopic LASIK and surface ablation. It results in halos around point images. Spherical aberration exacerbates myopia in low light (night myopia). In brighter conditions, the pupil constricts, blocking the more peripheral rays and minimizing the effect of spherical aberration. As the pupil enlarges, more peripheral rays enter the eye and the focus shifts anteriorly, making the patient slightly more myopic in low-light conditions. In general, the increase in overall wave aberration with pupil size has been reported to increase to approximately the second power of the pupil radius. This is because of the fact that most wave aberration is due to the 2nd order aberrations which have a square radius dependency.<ref name=Lombardo /> The effect of spherical aberration increases as the fourth power of the pupil diameter. Doubling pupil diameter increases spherical aberration 16 times.<ref name=ao2>{{cite book|title=Basic and Clinical Science Course, Section 3: Clinical Optics|year=2011-2012|publisher=American Academy of Ophthalmology|isbn=978-1615251100|pages=100|edition=2011-2012 last major rev. 2010-2012.}}</ref> Thus, a small change in pupil size can cause a significant change in refraction. This possibility should be considered in patients who have fluctuating vision despite well-healed corneas following keratorefractive surgery.
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| ''Coma'' is common in patients with decentred [[corneal graft]]s, [[keratoconus]], and decentred laser ablations.
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| ''Trefoil'' produces less degradation in image quality compared with coma of similar RMS magnitude.<ref name=ao>{{cite book|title=Basic and Clinical Science Course, Section 13: Refractive Surgery|year=2011-2012|publisher=American Academy of Ophthalmology|isbn=978-1615251209|pages=7–9|edition=2011-2012.}}</ref>
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| == Assessment and quantitative expression of ocular aberrations == | |
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| ===Assessment===
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| [[Image:Shack hartmann.jpg|thumb|350px|Shack Hartmannsystem]]
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| Many techniques for measuring the eye’s aberrations have been described, The most common technique is Shack-Hartmann aberrometry. Other methods include Tscherning systems, ray tracing and Skiascopy methods.<ref name=azar /><ref name=yanoff>{{cite book|last=Myron Yanoff, Jay S. Duker|title=Ophthalmology|year=2009|publisher=Mosby Elsevier|isbn=978-0-323-04332-8|pages=104|edition=3rd ed.}}</ref>
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| ===Quantitative expression===
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| ====<small>RMS</small>====
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| Quantitative comparisons between different eyes and conditions are usually made using [[root mean square|RMS]] (root mean square). In order to measure RMS, for each type of aberration the difference between the aberration and mean value is squared and averaged across the pupil area. Different kinds of aberrations may have equal RMS across the pupil but have different effects on vision, therefore, RMS error is unrelated to visual performance. The majority of eyes have total RMS values less than 0.3 µm.<ref name=ao />
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| ====<small>Zernike Polynomials</small>====
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| The most common method of classifying the shapes of aberration maps is to consider each map as the sum of fundamental shapes or basis functions. One popular set of basis functions are the [[Zernike polynomials]].<ref name=azar /> Each aberration may be positive or negative in value and induces predictable alterations in the image quality.<ref name=applegate>{{cite journal|last=Applegate|first=RA|coauthors=Thibos, LN; Hilmantel, G|title=Optics of aberroscopy and super vision.|journal=Journal of cataract and refractive surgery|date=2001 Jul|volume=27|issue=7|pages=1093–107|pmid=11489582}}</ref>
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| Because there is no limit to the number of terms that may be used by Zernike polynomials, vision scientists use the first 15 polynomials, based on the fact that they are enough to obtain a highly accurate description of the most common aberrations found in human eye.<ref>{{cite journal|last=Thibos|first=LN|coauthors=Applegate, RA; Schwiegerling, JT; Webb, R|title=Report from the VSIA taskforce on standards for reporting optical aberrations of the eye.|journal=Journal of refractive surgery (Thorofare, N.J. : 1995)|date=2000 Sep-Oct|volume=16|issue=5|pages=S654-5|pmid=11019893}}</ref> Among these the most important Zernike coefficients affecting visual quality are coma, spherical aberration, and trefoil.<ref name=ao />
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| Zernike polynomials are usually expressed in terms of polar coordinates (ρ,θ), where ρ is radial coordinate and θ is the angle. The advantage of expressing the aberrations in terms of these polynomials includes the fact that the polynomials are independent of one another. For each polynomial the mean value of the aberration across the pupil is zero and the value of the coefficient gives the RMS error for that particular aberration (i.e. the coefficients show the relative contribution of each Zernike mode to the total wavefront error in the eye).<ref name=Charman>{{cite journal|last=Charman|first=WN|title=Wavefront technology: past, present and future.|journal=Contact lens & anterior eye : the journal of the British Contact Lens Association|date=2005 Jun|volume=28|issue=2|pages=75–92|pmid=16318838|doi=10.1016/j.clae.2005.02.003}}</ref> However these polynomials have the disadvantage that their coefficients are only valid for the particular pupil diameter for which they are determined.
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| In each Zernike polynomial <math>Z^m_n</math>, the subscript n is the '''order of aberration''', all the Zernike polynomials in which n=3 are called third-order aberrations and all the polynomials with n=4, fourth order aberrations and so on. <math>Z^2_4</math> and <math>Z^{-2}_4</math> are usually called secondary Astigmatism and should not cause confusion. The superscript m is called the '''angular frequency''' and denotes the number of times the Wavefront pattern repeats itself.<ref name=Charman />
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| List of Zernike modes and their common names:<ref name=Wyant>{{cite web|last=Wyant|first=James C|title=Zernike Polynomials|url=http://wyant.optics.arizona.edu/zernikes/zernikes.htm}}</ref>[[Image:Zernike polynomials2.png|300px|thumb|Plots of Zernike polynomials in the unit disk]]
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| {| class="wikitable"
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| ! Zernike Term !! Name
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| | <math>Z^0_0</math> || Piston
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| | <math>Z^1_1</math>, <math>Z^{-1}_1</math> || Tilt (Prism)
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| | <math>Z^0_2</math> || Defocus
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| | <math>Z^2_2</math>, <math>Z^{-2}_2</math> || Astigmatism
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| | <math>Z^2_4</math>, <math>Z^{-2}_4</math> || Secondary Astigmatism
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| | <math>Z^0_4</math> || Spherical Aberration
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| | <math>Z^1_3</math>,<math>Z^{-1}_3</math> || Coma
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| | <math>Z^3_3</math>, <math>Z^{-3}_3</math> || Trefoil
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| | <math>Z^4_4</math>, <math>Z^{-4}_4</math> || Quadrafoil
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| |}
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| == Management ==
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| Low order aberrations (hyperopia, Myopia and regular astigmatism), are correctable by [[glasses|eyeglasses]], [[Contact lens|soft contact lenses]] and [[refractive surgery]]. Neither spectacles nor soft contact lenses nor routine keratorefractive surgery adequately corrects high order aberrations. Significant high order aberration usually requires a [[rigid gas permeable|rigid gas-permeable]] contact lens for optimal visual rehabilitation.<ref name=ao />
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| Customized Wavefront-guided refractive corneal laser treatments are designed to reduce existing aberrations and to help prevent the creation of new aberrations.<ref name=ao /> The wavefront map of the eye may be transferred to a Lasik system and enable the surgeon to treat the aberration. Perfect alignment of the treatment and the pupil on which the Wavefront is measured is required, which is usually achieved through iris feature detection. An efficient eye tracking system and small spot size laser is necessary for treatment . Wavefront customization of ablation increases the depth of ablation because additional corneal tissue must be ablated to compensate for the high order aberrations.<ref name=azar /> Actual results with Wavefront guided LASIK showed that not only it cannot remove HOA but also the optical aberrations are increased. However, the amount of increase in aberrations are less than conventional Lasik.<ref>{{cite journal|last=Kohnen|first=T|coauthors=Bühren, J; Kühne, C; Mirshahi, A|title=Wavefront-guided LASIK with the Zyoptix 3.1 system for the correction of myopia and compound myopic astigmatism with 1-year follow-up: clinical outcome and change in higher order aberrations.|journal=Ophthalmology|date=2004 Dec|volume=111|issue=12|pages=2175–85|pmid=15582071|doi=10.1016/j.ophtha.2004.06.027}}</ref> Corneal optical aberrations after photorefractive keratectomy with a larger ablation zone and a transition zone are less pronounced and more physiologic than those associated with first-generation (5 mm) ablations with no transition zone.<ref>{{cite journal|last=Endl|first=MJ|coauthors=Martinez, CE; Klyce, SD; McDonald, MB; Coorpender, SJ; Applegate, RA; Howland, HC|title=Effect of larger ablation zone and transition zone on corneal optical aberrations after photorefractive keratectomy.|journal=Archives of ophthalmology|date=2001 Aug|volume=119|issue=8|pages=1159–64|pmid=11483083}}</ref>
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| Aspherical [[intraocular lens]]es (IOLs) have been used clinically to compensate for positive corneal spherical aberrations. Although Aspherical IOLs may give better contrast sensitivity, it is doubtful, whether they have a beneficial effect on distance visual acuity. Conventional (not Aspherical) IOLs give better depth of focus and better near vision. The reason for improved depth of focus in conventional lenses is linked to residual spherical aberration. The small improvement in depth of focus with the conventional IOLs enhances uncorrected near vision and contribute to reading ability.<ref>{{cite journal|last=Nanavaty|first=MA|coauthors=Spalton, DJ; Boyce, J; Saha, S; Marshall, J|title=Wavefront aberrations, depth of focus, and contrast sensitivity with aspheric and spherical intraocular lenses: fellow-eye study.|journal=Journal of cataract and refractive surgery|date=2009 Apr|volume=35|issue=4|pages=663–71|pmid=19304086|doi=10.1016/j.jcrs.2008.12.011}}</ref>
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| Wavefront customized lenses can be used in eyeglasses. Based on Wavefront map of the eye and with the use of laser a lens is shaped to compensate for the aberrations of the eye and then put in the eyeglasses. Ultraviolet Laser can alter the refractive index of curtain lens materials such as epoxy polymer on a point by point basis in order to generate the desired refractive profile.<ref name=cervino />
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| Wavefront customized contact lenses can theoretically correct HOA. The rotation and decentration reduces the predictability of this method.<ref name=cervino />
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| ==See also==
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| * [[Optical aberrations]]
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| * [[Wavefront]]
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| * [[Zernike polynomials]]
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| ==References==
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| {{Reflist}}
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| [[Category:Vision]]
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| [[Category:Disorders of ocular muscles, binocular movement, accommodation and refraction]]
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As head of Louis Vuitton, Yves Carcelle, who has died at the age of 66, built the French fashion house into one of the world's leading luxury brands.
Though it is only one of around 60 such brands owned by LVMH, Louis Vuitton is the conglomerate's driving force, and Carcelle expanded its appeal into areas such as eyewear and jewellery while travelling the world looking for new areas to colonise. One of his key decisions came in 1997 when he hired as creative director the then up-and-coming designer Marc Jacobs, whose introduction of the company's first ready-to-wear line helped seal its place at or near the top of fashion's premier league.
Born in 1948 in Paris, Carcelle graduated in mathematics from the city's �cole Polytechnique then gained a masters in business administration from the business school, Insead. His first job was as a salesman for Spontex a maker of household cleaning products, which he said was excellent training for a career in fashion: "You have to be a good salesmen, if nothing else," he said.
"And you have to know how to deal with people,"
The renowned fashion journalist Suzy Menkes wrote: "My favourite Yves Carcelle story - one he liked to tell with a glass of champagne in hand, perhaps at a private party at home in front of a bold Gilbert & George painting, with his then wife Rebecca at his side and with his boys listening in - was about his early days as a fledgling travelling salesman. Taking to the road with a girlfriend, the young Yves would send her into a hardware store asking with a flirtatious enthusiasm for a new product he was hoping to sell. Ten minutes later, he would be knocking on the same store door, offering to supply the goods. The success was instant."
Following his stint at Spontex, in 1974 he joined Blenda Pharm laboratories, then five years later was appointed director of the Absorba clothing brand at Poron. In 1985 he became president of the textiles firm Descamps, and his success in turning the company around led to his recruitment by Bernard Arnault as LVMH's director of strategy in 1989.
The following year he became chairman and CEO, then in 1998 head of the LVMH fashion division, which as well as Louis Vuitton includes such brands as Givenchy, Donna Karan, Christian Dior, Celine, Fendi, the jewellers Bulgari and cognac maker Hennessy.
Colleagues said Carcelle knew little about luxury when he joined Louis Vuitton. But he quickly won Arnault's trust and became one of his most respected lieutenants. "There was a lot of mutual respect between the two men even though they had very different personalities," an LVMH executive.
"Carcelle was very different from Arnault. Arnault is cold and not really somebody who easily gets excited about something, while Carcelle was very spontaneous and open."
Carcelle quadrupled Louis Vuitton's network of stores to just under 470, many of them in strategically important emerging markets such as China. He showed great skill in spreading the Louis Vuitton gospel: a rival told Suzy Menkes how when he and Carcelle would arrive in an often remote Chinese town, Carcelle would hand out beautifully wrapped small leather goods as gifts to the city's mayor and each member of his family.
In 2001 he went back to his old job following the departure of Marcello Bottoli after only 18 months. "It's not always easy to sum up what our brand means to people, but let me try," he said in 2004. "It's about reliability, quality, style, innovation and authenticity."
Carcelle became an expert in easing Louis Vuitton into new markets. When he wasn't globe-trotting, Carcelle was usually in his Paris office by 6am. Though he was softly-spoken, he could raise his voice when necessary - as he did when he let fly at a French government official who went to a Louis Vuitton store opening in Bangkok carrying a fake Vuitton bag.
Carcelle, who died of renal cancer, stepped down at the end of 2012 as Louis Vuitton's sales growth was starting to slow down after years of double-digit increases. There were calls for a change in management, particularly as Carcelle was in his early 60s. He stayed on as part of the LVMH executive committee and as vice president of the Fondation Louis Vuitton museum, designed by Frank Gehry on the Bois de Boulogne and due to open next month.
A keen sailor, he was an enthusiastic follower of the Louis Vuitton Cup, which until last year served as the eliminator series for the Americas Cup. Just before the onset of the global financial crisis he was asked if he was worried that his company could suffer.
"Not really," he replied. "The great thing about our business is that our customers are very rich - and then they are a bit less rich, but still rich, right?"
Yves Carcelle, businessman: born Paris 18 May 1948; Chevalier de http://www.pcs-systems.co.uk/Images/celinebag.aspx la L�gion d'honneur 2014; twice married (five children); died 31 August 2014.