Each keratoconus is unique and should be evaluated ...
Transcript of Each keratoconus is unique and should be evaluated ...
Eachkeratoconusisuniqueandshouldbeevaluatedindividuallyandsystematizedtodefinethemostappropriatesurgicalapproach.Adetailedanalysisofmultiple
tomographic,refractive,visualandaberrometricvariablesisessentialforgoodsurgicalplanningandconsequentsatisfactoryresults.
PhilosophyofKeraring®surgicalplanning
SYMMETRICICRS
ModelSI-5(5mmOZ).Allarcsavailablefrom150µmto350µmin50µmsteps
90 120 160 210 325
ModelSI-6(6mmOZ).Allarcsavailablefrom150µmto350µmin50µmsteps
90 120 150 210
5mm / 160º
6mm / 150º
ASYMMETRICICRS
ARC160º(AS5andAS6)OPTICALZONE5mmand6mmTHICKNESSPROGRESSION:150-250µmand200-300µmDIRECTIONOFSEGMENTTHICKNESSPROGRESSION:Clockwiseandanti-clockwise
n Arc330º(AS5330)OpticalZone:5mmProgressiveThicknesses:150-250or200-300µm
Directionofthicknessincrease:Thinnerontips,thickerinthecenterofthearc
Arc330ºASD5330)SinusoidalThickness150/250/150µm200/300/200µmDirectionofthicknessincrease:Thinnerontipsandonthecenter,thickeronthesides.
ü Newnomogramforsurgicalplanningbasedonspecificalgorithmsforeachmorphologicaltypeofkeratoconusandseverity.
ü Newcriteriaforopticalzoneselection,implantationaxis,andsizespecification
ü Incorporatesthelatestimplants(asymmetricandlongarcICRS)
Keraring®:Nomogram2018
ü Cornealtomography(4maps):axialcurvature,anteriorandposteriorelevationBFS,pachymetry
ü Aberrometricmap:ComamagnitudeandaxisZ3-1andZ31
ü Subjectiverefraction:Minuscylinder
ü Visualacuity:UCVAandBCVA
ü Pupildiameter(mesopicconditions)
ü Visualpotentialwithahardcontactlenstestorpinholetest
ü Surgicaltechnique:MechanicalorFSlaser-assisted.
ü Keratoconusmorphologicalclassification(AlfonsoClassification)
RequireddataforKeraringsurgicalplan
AlfonsoMorphologicalClassificationof
KeratoconusTheAlfonsoMorphologicalClassificationofKeratoconusdefinesspecificphenotypicalpresentationsofthediseaseforimplantationofintrastromalcornealrings.IthasbeendevelopedbyProfessorJoseF.AlfonsoofInstitutoOftalmologicoFernandez-Vega(Oviedo,Spain).5typesofkeratoconusaredefinedaccordingtothefollowingtomographicparameters:ü Locationoftheconeü Relationshipbetweenthe3maindiagnosticaxes(flatrefractive,flat
topographicandcoma)ü Orthogonalityoftopographicastigmatismü Symmetryoftopographicastigmatismü Topographicaspectofanteriorcurvaturemap
AlfonsoClassification
Locationofthecone:distancefromthecentretotheapexoftheconeonposteriorelevationmap
Type Distanceinmm.
Central <0.75
Paracentral Between0.76and1.80
Pericentral ≥1.81
Central Paracentral Pericentral
AlfonsoClassification
Relationshipbetweenaxes:Divergencebetweentheflatrefractiveaxis,flattopographicaxisandthecomaaxis.
Type Divergenceindegrees
Coincident <30
Non-coincident 31~60
Perpendicular 61~120
Coincident Comanon-coincident
Refr.axis
Topoaxis
Comaaxis
Refract.Perpendicular
AlfonsoClassification
Orthogonalityofastigmatism:angulationbetweenthelobesoftopographicastigmatism
Type Angulationindegrees
Regular ≤20
Irregular ≥21
Regular Irregular
AlfonsoClassification
SymmetryofAstigmatism:Symmetrybetweenthelobesoftopographicastigmatism
Type
Symmetrical(lobesofsimilarsize)
Asymmetrical(lobesofdifferentsize)
Symmetrical Asymmetrical
AlfonsoClassification-Summary
Type Location Relationbetweenaxes
Astigmaticorthogonality
Astigmaticsymmetry
Topographicaspect
1
ParacentralorPericentral
Refractive,topographicand
comacoincidental(≤30º)
Irregular
Symmetrical
“croissant”
2
Paracentral
Refractiveflatandcomanon
coincidental(>30<60)
Irregular
Asymmetrical
“duck”
3
ParacentralorPericentral
Topographicandcomaperpendicular
Regular
Asymmetrical
“snowman”
4
Central
Non-determinant Irregular
Non-determined
“nipple”
5
Central
Refractiveandtopocoincidental.Comanon-determinant
Regular
Symmetrical
“bowtie”
Keraring®SurgicalPlanning
ConeType1
Type Location Relationbetweenaxes
Astigmaticorthogonality
Astigmaticsymmetry
Topographicaspect
1
ParacentralorPericentral
Refractive,topographicand
comacoincidental(≤30º)
Irregular
Symmetrical
“croissant”
Primarycriterionforimplantselection:1. Topographicastigmatismorrefractive
(whicheverishigher)
Implantselection–Conetype1
Conetype
No.ofsegments(arcs)
Axisofimplantation
Opticalzone Segmenttype
1
1(160)or2(160+90)
Flattopographic
K2≥52D=5mmK2≤51D=6mm
Symmetrical
AstigmatismD. Arc/Implantthickness
≤2.5 160/150
2.5~3.5 160/200
3.5~4.5 160/250
4.5~5.5 160/300
AstigmatismD. Arc/Implantthickness
5.5~6.5 160/300+90/150
6.5~8 160/300+90/200
>8 160/300+90/250
ConeType2
Variablesforimplantselection:1. Meankeratometry2. Magnitudeofastigmatism3. Relationbetweenthediagnosticaxes
Type Location Relationbetweenaxes
Astigmaticorthogonality
Astigmaticsymmetry
Topographicaspect
2
Paracentral
Flattopographicandcomanon-
coincidental(>30<60)
Irregular
Asymmetrical
“duck”
Implantselection-ConeType2
Ifmeankeratometryis<52D.,use1segment(160ºasymmetric)or2segments(160ºasymmetric+120ºstandard),accordingtomagnitudeofastigmatism AstigmatismD. Arc/Implant
thickness
≤4 AS5150/250
4~6 AS5200/300
>6 AS5200/300+SI5120/200
Axisofimplantation:Iftherefractiveaxisiscoincidentwiththetopographicflataxis,choosethebisectoraxisofthese.Iftherefractiveaxisiscoincidentcomaaxis,choosethebisectoraxisofthese.
Implantselection-ConeType2
Ifmeankeratometryis>52D.,use1segment(330ºasymmetric)accordingtothemeankeratometryvalue
MeankeratometryD. Arc/Implantthickness
52~54 AS5330150/250
≥55 AS5330200/300
Axisofimplantation:Centreofthearcalignedtothecomaaxis
ConeType3
Primarycriterionforimplantselection:1. Meankeratometry2. Magnitudeandaxisofastigmatismand
coma3. Relationbetweenthediagnosticaxes
Type Location Relationbetweenaxes
Astigmaticorthogonality
Astigmaticsymmetry
Topographicaspect
3
ParacentralorPericentral
Topographicandcomaperpendicular
Regular
Asymmetrical
“snowman”
SubType3A
SubType3B
DifferentiationbySubTypes:3A–Flatrefractiveaxisandflattopographicaxiscoincident3B–Flatrefractiveaxisandflattopographicaxisperpendicular
Implantselection-Cone3A
Ifmeankeratometryis<52D.,use2segments(160asymmetric)accordingtothemagnitudeoftopographiccylinder
Axisofimplantation:Flattopographic
AstigmatismD. Arc/Implantthickness
≤4 2xAS5160150/250(CandW)
>4 2xAS5160200/300(CandW)
Implantselection-Cone3A
Ifmeankeratometryis>52D.,use1segment(asymmetric330degrees)accordingtomeankeratometryvalue.
Axisofimplantation:Steeptopographic
MeankeratometryD. Arc/Implantthickness
52~54 AS5330150/250
>54 AS5330200/300
Implantselection-Cone3B
Primarycriterionforimplantselection:1. MagnitudeandaxisofcomaAxisandcomaaberrationvalueZ3-1andZ31measuredinmicronsatthe5mmopticalzone.Usesymmetricsegment210ºatø5mm
Axisofimplantation:Comaaxis
Comaµm(5mm) Arc/Implantthickness
≤1.5 SI5210/200
1.5~2.5 SI5210/250
>2.5 SI5210/300
ConeType4
Primarycriterionforimplantselection:1. Meankeratometry2. Sphericalequivalent
Type Location Relationbetweenaxes
Astigmaticorthogonality
Astigmaticsymmetry
Topographicaspect
4
Central
Non-determinant
Irregular
Non-determinant
“nipple”
Implantselection–Cone4
Primarycriterionforimplantselection:1. Meankeratometry2. Sphericalequivalentrefraction• IfBCVA≥20/40,usethesphericalequivalent• IfBCVA<20/40,usethemeankeratometry• Usesymmetricalsegmentof325ºat5mmOZ.
Axisofimplantation:270º(inferior)
Sph.Eq.D. Meankeratometry
D.
Arc/Implantthickness
2~4 <48 SI5325/150
4~6 48~50 SI5325/200
6~8 50~52 SI5325/250
>8 >52 SI5325/300
ConeType5
Primarycriterionforimplantselection:1. Magnitudeandaxisofastigmatism2. Keratometry3. Refraction
Type Location Relationbetweenaxes
Astigmaticorthogonality
Astigmaticsymmetry
Topographicaspect
5
Central
Refractiveandtopocoincidental.Comanon-determinant
Regular
Symmetrical
“bowtie”
Implantselection:ConeType5
Primarycriterionforimplantselection:1. Magnitudeandaxisofastigmatism2. Keratometryandrefraction
• Ifthesubjectiverefractionshowsmixedorsimpleastigmatism,use2symmetricsegmentsof120ºaccordingtothemagnitudeofthetopographicastigmatism
Axisofimplantation:
Flattopographic
AstigmatismTopoD. Implantthicknessµm
≤4 150
4~6 200
6~8 250
>8 300
Implantselection:ConeType5
1. Magnitudeandaxisofastigmatism2. Keratometryandrefraction
• Iftherefractionpresentsmyopia≤3D.orifmeankeratometryis≤52D.implantoneAS5D150/250/150sinusoidalthicknessimplantasshown
• Iftherefractionpresentsmyopia>3D.orifmeankeratometryis>52D.,implantoneAS5D200/300/200sinusoidalthicknessimplantasshown
Axisofimplantation:Steeptopographic
ImplantDepthGuidelinesFemtosecondlaser-assistedtechnique:Minimumcornealthicknessmeasuredat5mmOZ(tunneltrack)shouldbe≥400µm.• Calculatethedepth:Minimumthicknessat5mmminus100µm• Rangeoftunneldepthsuggested:300µmminimum/400µmmaximum• Ifcalculateddepth>400µm,adjustdepthto400µm
MechanicaldissectiontechniqueSuggestedincisiondepth:80%ofcornealthicknessmeasuredintraoperativelyattheincisionsite PACHYMETRICSAFETYLIMITREFERENCETABLE(mechanicaldissectiononly)
Thicknessoftheproposedsegment 150µm 200µm 250µm 300µm 350µm
MINIMUMcornealthicknessrequiredinthetunnel
dissectionarea250µm 335µ 420µ 500µ 580µ
ü Theguidelinesprovidedinthenomogramsserveasastartingpointforsurgicalplanning.Itisrecommendedtojointlyevaluateallthediagnosticvariablesofthepatientandthecriteriaofthesurgeon,forbettercustomisationofthesurgicalplan.
Customisationofsurgicalplanning
ü TheKeraringAssistantapplication,availableforiOSandAndroidsystems,allowsthesurgeontosubmitclinicaldataanddiagnosticexamstorequestsurgicalplans,clarifyquestionsorobtainsecondopinions.
Mediphacosconsulting