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