激光治疗色素沉着 English文档格式.docx

激光治疗色素沉着 English文档格式.docx

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AbenaOOfori,MD

Disclosures:

AndreiMetelitsa,MD,FRCPCNothingtodisclose.ThomasRohrer,MDSpeaker'

sBureau:

Candela/Syneron[lasers（alexandritelaser）].Consultant/AdvisoryBoards:

Candela/Syneron[lasers（alexandritelaser）].KennethAArndt,MDNothingtodisclose.JeffreySDover,MD,FRCPCConsultant:

Medicis/Valeant[fillers,toxin];

Solta/Valeant[lasers,lights].Equity:

CVS/SkinEffects[skincare];

Shaser[IPLhairremoval（ilighthomedevice）];

SkyBiodevices[skincancerscreening].MedicalAdvisoryBoard:

Cutera[lasers,lights];

Cynosure[lasers,lights];

Kythera[fatsaponification（N/A）];

Lumenis[lasers,lights];

Myoscience[neuromuscular（N/A）];

Topokine[fatmodulation（biologics）];

Zeltiq[bodycontouring].ResearchGrant:

Allergan[neuromodulators,fillers];

Evolus[neuromodulator];

Medicis/Valeant[filler,toxin];

Merz[toxin,filler];

Myoscience（neuromuscular（N/A）];

Shaser[IPLhairremoval];

SoltaValeant[lasers,lights];

Suneva[filler（filler）];

Syneron[bodycontouring];

Zeltiq（bodycontouring（CoolSculpting）].UseofEquipment:

Solta/Valeant[lasers,lights（Fraxel）].AbenaOOfori,MDNothingtodisclose.

Contributordisclosuresarereviewedforconflictsofinterestbytheeditorialgroup.Whenfound,theseareaddressedbyvettingthroughamulti-levelreviewprocess,andthroughrequirementsforreferencestobeprovidedtosupportthecontent.AppropriatelyreferencedcontentisrequiredofallauthorsandmustconformtoUpToDatestandardsofevidence.

Conflictofinterestpolicy

Alltopicsareupdatedasnewevidencebecomesavailableandourpeerreviewprocessiscomplete.

Literaturereviewcurrentthrough:

Jul2015.|Thistopiclastupdated:

Apr30,2015.

INTRODUCTION 

— 

Lasersandintensepulsedlightareusefulforthetreatmentofawidevarietyofdisorderscharacterizedbythepresenceofcutaneoushyperpigmentation.Themechanismsbywhichthesetherapiesimprovehyperpigmentationincludephotothermal,photomechanical,andablativeeffects.

Thoroughknowledgeoftheprinciplesthatgoverntheinteractionbetweenlightandskinisessentialforthesuccessfulandsafeclinicalapplicationoflasersandintensepulsedlight.Knowledgeofthelesiontypeandlesionalhistopathologiccharacteristicsarecriticalfortheselectionofanappropriatelight-basedtherapy.

Theprinciplesoflaserandintensepulsedlighttherapyforhyperpigmentedskinlesions,thelasersusedforthisindication,andthetherapeuticoptionsforselectdisordersofhyperpigmentationwillbediscussedhere.Thegeneralprinciplesofmedicallasersandmoreinformationontheprinciplesoftreatmentofcutaneouslesionswithlaserandintensepulsedlightarereviewedelsewhere.（See"

Basicprinciplesofmedicallasers"

and"

Principlesoflaserandintensepulsedlightforcutaneouslesions"

.）

PRINCIPLES 

Theuseoflaserandintensepulsedlighttherapyforcutaneoushyperpigmentationisbasedupontheclinicalapplicationofthetheoryofselectivephotothermolysis,atheorythatdescribesthemechanismbywhichlightcanbeusedtoexertspecificeffectsontheskin[1].（See"

sectionon'

Selectivephotothermolysis'

Thebasicprinciplesofselectivephotothermolysisareasfollows[1]:

●Thewavelengthoflightdeliveredshouldbepreferentiallyabsorbedbythetargetmolecule（alsoknownasachromophore）

●Lightmustbedeliveredwithinaperiodoftimethatlimitsdamagetoadjacentcutaneousstructures

●Thelightenergytransferredtothetargetchromophoremustbesufficienttoexertthedesiredtherapeuticeffectwhileminimizingdamagetoadjacenttissue

Sinceanexcessofmelaninintheskinisresponsibleforthedarkenedappearanceofmostcutaneousdisordersofhyperpigmentation,melaninfrequentlyisthechromophoretargetedduringtreatment.

Lightwavelength 

Stronglightabsorptionbymelaninoccursintheultravioletrangeoftheelectromagneticspectrumandthemolecule'

saffinityforlightdecreasesprogressivelyaswavelengthsrise（figure1）.Althoughonemightinterpretthistomeanthatlasersthatemitultravioletlightorshortwavelengthsofvisiblelightwouldbepreferredforthetreatmentofhyperpigmentation,additionalfactorssuchascompetitionwithhemoglobin（achromophorewithpeaklightabsorptionbetween400and600nm）andthelimiteddepthofpenetrationofveryshortwavelengthsoflightnarrowthespectrumofoptimalclinicaluse.

Thus,theidealwavelengthsoflightforabsorptionbymelaninintheskinfallbetween600and1100nm.TheQ-switched（QS）lasers,nonablativepulsedlasers,andintensepulsedlightsourcesmostcommonlyusedforthetreatmentofcutaneoushyperpigmentationemitwavelengthsoflightwithinthisrange.Incontrast,theefficacyofablativelasersandfractionatedlasersforhyperpigmentedskinlesionsisnotbaseduponmelaninasatargetchromophore;

theselaserstargetwaterintheskin.Wavelengthsbetween1550and10,600nmarestronglyabsorbedbywaterandareutilizedforablativeandfractionaltherapy.（See"

Wavelength'

Withtheexceptionofwater-targetingablativelasers,inwhichstrongabsorptionoflightbywaterintheskinlimitstheamountoflighttransmittedtothedermis,thedepthoflightpenetrationintotheskingenerallyincreaseswithincreasinglaserwavelength.Thus,knowledgeofthesiteofabnormalmelanindepositionwithintheskiniscriticalfordeviceselection.Whilesomedisorders,suchaslentiginesarecharacterizedbyincreasedmelaninintheepidermis,dermalhyperpigmentationisasignificantfeatureinotherskindiseases（see'

Indications'

below）.Laserswithrelativelyshortwavelengths（eg,532nmfrequencydoubledQSNd:

YAGlasers）arewellsuitedfortheeliminationofepidermalmelanin,andlongerwavelengthlasers（eg,694nmQSruby,755nmQSalexandrite,and1064nmQSneodymium:

yttriumaluminumgarnet[Nd:

YAG]lasers）aretypicallyemployedforthetreatmentoflesionsinwhichmelanindepositsaredeeper.（See"

Pulseduration 

Thepulsedurationofadevice（lengthoftimeoverwhichlightisdelivered）isanadditionalfactorthathasasignificantimpactontheefficacyoftreatment.Whenlightemittedfromalaserorintensepulsedlightdeviceisabsorbedbythetargetchromophore（eg,melanin）,aphotothermaleffect,resultingfromtheconversionoflightenergyintoheat,leadstothecoagulationofthetargettissue.Thedeliveryoflightinaperiodshorterthanatarget'

sthermalrelaxationtime（thetimenecessaryforatargettocoolby50percent）allowsforthedestructionofthetargetwhilelimitingthetransferofheattoadjacenttissues.Asanexample,thethermalrelaxationtimeofanindividualmelanosomeisbetween50and500ns,andthepulsedurationsoftheQSlaserscommonlyusedforthetreatmentofpigmentedlesionsareinthenanosecondrange.

Extendingthepulsedurationcanbebeneficialforthetreatmentoflargestructures.Becauselargestructureshavelongerthermalrelaxationtimesandloseheatmoreslowlythansmallstructures,longpulsedurationsleadtorelativelygreateraccumulationofheatinlargestructures.Inthisway,largerstructures（eg,alargenestofpigment-containingnevomelanocytes）canbepreferentiallydestroyedwhilesparingsmaller,unintendedtargetsthatalsocontainmelaninorotherlight-absorbingchromophores.（See"

Pulseduration'

Inadditiontophotothermaleffects,laserscanalsoremovemelaninviaphotomechanicaleffects（alsoreferredtoasphotoacousticeffects）.Veryrapiddeliveryofhighenergypulsesoflightthatishighlyabsorbedbymelanincanleadtothecreationofshockwaveswithinmelanosomes,resultinginmelanosomerupture.TheQSlaserstakeadvantageofthisfeature.（See'

Q-switchedlasers'

below.）

Fluence 

Lastly,thefluence（theamountoflightenergydeliveredperunitofspace）isakeydeterminantforachievingthedesiredclinicaleffect.Fluencesettingsthataretoohighcanleadtoadverseeffectssuchasdyspigmentationandscarring,andfluencesettingsthataretoolowresultininadequatetreatment.Excessivefluencesettingsareparticularlydetrimentalinindividualswithdarkskinpigmentation,aspermanenthypopigmentationmayresultfromtreatment.（See"

Fluence'

DEVICES 

Awidevarietyoflight-emittingdevicesareusefulforthetreatmentofpigmentedskinlesions.Asdescribedabove,thewavelengthandpulsedurationofaparticulardeviceareimportantdeterminantsoftheclinicalscenariosforwhichitismostuseful.

Q-switchedlasers 

Q-switched（QS）lasersdeliverexceptionallyhighenergylaserpulseswithpulsedurationsinthenanosecondrange.Absorptionoflightemittedinthisfashionbymelanincanleadtotheremovalofmelaninviathecreationofacousticshockwaveswithinmelanosomes.Q-switchedlasersalsooperateviaphotothermaleffects.（See'

Principles'

above.）

QSlasersareavailableinavarietyofwavelengths.Commonlyusedvarietiesincludethe694nmQSruby,755nmQS