医学课件：硬镜的设计.ppt

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1、DESIGNINGARIGIDCONTACTLENSDesigningaRigidContactLensLensdesignisintendedtoprovide:OptimalvisionOptimalcomfortMinimalocularchangesMustselectbestsize,curvatureandpowerLensshouldhavegoodposition,movement,stability,andlens-to-cornearelationshipZoneSizesLensDiameterOpt

2、icZoneDiameterPeripheralCurveWidthsLensDiameterRangeforrigidlenses:8-11mmDiameterselectionisbasedon:FittingphilosophyLidattachment:largerdiameter:9.2mmorgreaterInterpalpebral:smallerdiameter:9.2mmorsmallerLidpositionandaperturesizeNormallids(upperlid1/6-1/3intothec

3、orneaandlowerlidatornearlimbus):tryforlidattachmentHighupperlid:fitinterpalpebralLensDiameterRangeforrigidlenses:8-11mmDiameterselectionisbasedon:Cornealdiameter(HVID)Largercorneasrequirelargerdiameterse.g.,10mmcornea:use8.8mm11mmcornea:use9.2mm12mmcornea:use9.6mm

4、CornealcurvatureFlattercorneasusuallyrequirelargerdiametersSteepercorneasusuallyrequiresmallerdiametersstartwith9.2mmOpticZoneDiameterChosentocoverpupilindimilluminationtominimizeflareUsually1.2-1.6mmsmallerthanLDTypicalrange7.4-8.4mmLargerpupilsrequirelargerOZDssta

5、rtwith8.0mmSecondaryandPeripheralCurveWidthsUsetricurveortetracurve:largerLDrequiremorePC'sPeripheralCurvewidthusually0.2-0.4mmSecondaryCurvewidthapproximately2xPCwIfIntermediateCurveexists,allcurvesapproximatelyequalinwidth(SCwandICwusuallyslightlywiderthanPCw)SCw=

6、0.4mmandPCw=0.2mmZoneCurvaturesBasecurveradiusPeripheralcurveradiiBaseCurveKeratometryBasecurveisgenerallyselected0.50Dto1.00Dflatterthantheaveragecornealcurvaturetomaintainevenalignmentwithcornea:ForsmallLD/OZD(9.2/8.0):BC=Kave–0.50DForlargeLD/OZD(9.6/8.4):BC=Kave

7、–1.00DEx:Fora9.2/8.0designK=45.00DBC=44.50DBasecurveradiusSecondaryandPeripheralCurveRadiusChosentoprovideanaxialedgeliftof0.08-0.18mmAlwaysflatterthantheBCrtofittheflattermid-peripheralandperipheralcorneaTheflattertheBCr,theflattertheSCrandPCrOtherParametersPower

8、CenterThicknessEdgeThicknessEdgeShapeJunctionBlendsEdgeThicknessIncreaseinminuspower:greaterETIdealedgeprofileoccursatapprox-3.00DPower-2.