EN ISO 9913-2:2000

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Optics and optical instruments - Contact lenses - Part 2: Determination of oxygen permeability and transmissibility by the coulometric method (ISO 9913-2:2000)Optik und optische Instrumente - Kontaktlinsen - Teil 2: Bestimmung der Sauerstoff-Permeabilität und -Transmissibilität nach dem coulometrischen Verfahren (ISO 9913-2:2000)Optique et instruments d'optique - Lentilles de contact - Partie 2: Détermination de la perméabilité a l'oxygene et de la transmissibilité de l'oxygene avec la méthode coulométrique (ISO 9913-2:2000)Optics and optical instruments - Contact lenses - Part 2: Determination of oxygen permeability and transmissibility by the coulometric method (ISO 9913-2:2000)11.040.70Oftalmološka opremaOphthalmic equipmentICS:Ta slovenski standard je istoveten z:EN ISO 9913-2:2000SIST EN ISO 9913-2:2001en01-november-2001SIST EN ISO 9913-2:2001SLOVENSKI
STANDARD
ReferencenumberISO9913-2:2000(E)©ISO2000INTERNATIONALSTANDARDISO9913-2Firstedition2000-02-15Opticsandopticalinstruments—Contactlenses—Part2:DeterminationofoxygenpermeabilityandtransmissibilitybythecoulometricmethodOptiqueetinstrumentsd'optique—Lentillesdecontact—Partie2:Déterminationdelaperméabilitéàl'oxygèneetdelatransmissibilitédel'oxygèneaveclaméthodecoulométriqueSIST EN ISO 9913-2:2001

ISO9913-2:2000(E)PDFdisclaimerThisPDFfilemaycontainembeddedtypefaces.InaccordancewithAdobe'slicensingpolicy,thisfilemaybeprintedorviewedbutshallnotbeeditedunlessthetypefaceswhichareembeddedarelicensedtoandinstalledonthecomputerperformingtheediting.Indownloadingthisfile,partiesacceptthereintheresponsibilityofnotinfringingAdobe'slicensingpolicy.TheISOCentralSecretariatacceptsnoliabilityinthisarea.AdobeisatrademarkofAdobeSystemsIncorporated.DetailsofthesoftwareproductsusedtocreatethisPDFfilecanbefoundintheGeneralInforelativetothefile;thePDF-creationparameterswereoptimizedforprinting.EverycarehasbeentakentoensurethatthefileissuitableforusebyISOmemberbodies.Intheunlikelyeventthataproblemrelatingtoitisfound,pleaseinformtheCentralSecretariatattheaddressgivenbelow.©ISO2000Allrightsreserved.Unlessotherwisespecified,nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromeitherISOattheaddressbeloworISO'smemberbodyinthecountryoftherequester.ISOcopyrightofficeCasepostale56CH-1211Geneva20Tel.+41227490111Fax+41227341079E-mailcopyright@iso.chWebwww.iso.chPrintedinSwitzerlandii©ISO2000–AllrightsreservedSIST EN ISO 9913-2:2001

ISO9913-2:2000(E)©ISO2000–AllrightsreservediiiContentsPageForeword.iv1Scope.12Normativereferences.13Termsanddefinitions.24Principle.35Reagentsandmaterials.46Apparatus.47Testsamples.78Conditioningoftestsamples.89Procedure.810Testreport.10SIST EN ISO 9913-2:2001

ISO9913-2:2000(E)iv©ISO2000–AllrightsreservedForewordISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISOmemberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnicalcommittees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhastherighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,inliaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnicalCommission(IEC)onallmattersofelectrotechnicalstandardization.InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3.DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting.PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote.AttentionisdrawntothepossibilitythatsomeoftheelementsofthispartofISO9913maybethesubjectofpatentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.InternationalStandardISO9913-2waspreparedbyTechnicalCommitteeISO/TC172,Opticsandopticalinstruments,SubcommitteeSC7,Ophthalmicopticsandinstruments.ISO9913consistsofthefollowingparts,underthegeneraltitleOpticsandopticalinstruments—Contactlenses:Part1:DeterminationofoxygenpermeabilityandtransmissibilitywiththeFATTmethodPart2:DeterminationofoxygenpermeabilityandtransmissibilitybythecoulometricmethodSIST EN ISO 9913-2:2001

INTERNATIONALSTANDARDISO9913-2:2000(E)©ISO2000–Allrightsreserved1Opticsandopticalinstruments—Contactlenses—Part2:Determinationofoxygenpermeabilityandtransmissibilitybythecoulometricmethod1ScopeThispartofISO9913describesacoulometricmethodforthedeterminationofoxygenpermeabilityofbothrigidandnon-hydrogelflexiblecontactlensmaterialsandoxygentransmissibilityofrigidandnon-hydrogelflexiblecontactlenses.Itspecifiestheproceduresforthemeasurementsandestablishestheconditionsunderwhichmeasurementsaremade.ThispartofISO9913isapplicabletothedeterminationofoxygentransmissibilityofrigidandnon-hydrogelflexiblecontactlenses,incorporatingvariousrefractivepowersandradiallysymmetriccontactlensgeometries,andtheoxygenpermeability(Dk)ofrigidandnon-hydrogelflexiblecontactlensmaterialsintheformofstandardizedtestsamples.ThispartofISO9913isespeciallyusefulforthedeterminationofpermeabilityvaluesabove7510–11(cm2/s)[mlO2/(mlhPa)],whichfallabovetheusualrangeofthestandardpolarographicmethodofmeasurement(FATTmethod,seeISO9913-1).ThispartofISO9913isnotapplicabletohydrogelmaterialsorhydrogelcontactlenses.2NormativereferencesThefollowingnormativedocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthispartofISO9913.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthesepublicationsdonotapply.However,partiestoagreementsbasedonthispartofISO9913areencouragedtoinvestigatethepossibilityofapplyingthemostrecenteditionsofthenormativedocumentsindicatedbelow.Forundatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIECmaintainregistersofcurrentlyvalidInternationalStandards.ISO5725(allparts),Accuracy(truenessandprecision)ofmeasurementmethodsandresults.ISO8320:1986,Opticsandopticalinstruments—Contactlenses—Vocabularyandsymbols.ISO9339-1:1996,Opticsandopticalinstruments—Contactlenses—Determinationofthethickness—Part1:Rigidcontactlenses.ISO9913-1:1996,Opticsandopticalinstruments—Contactlenses—Part1:DeterminationofoxygenpermeabilityandtransmissibilitywiththeFATTmethod.SIST EN ISO 9913-2:2001

ISO9913-2:2000(E)2©ISO2000–Allrightsreserved3TermsanddefinitionsForthepurposesofthispartofISO9913,thetermsanddefinitionsgiveninISO8320apply,togetherwiththefollowing.3.1oxygenfluxjnetvolumeofoxygengaspassingthroughaunitareaofsamplecontactlensmaterialperunittimeunderspecifiedconditions,includingtemperature,samplethickness,andpartialpressuresofoxygenonbothsidesofthesampleNOTEAconvenientunitofoxygenfluxforcontactlensmaterialsisl/(cm2s).Intermsofmeasurementusingthecoulometricmethod,jisequaltotherateofoxygenflowpastthecoulometricoxygensensorqVdividedbytheareaofsample(A)throughwhichtheoxygenhaspassed.3.2oxygenpermeabilityDkoxygenflux(j)underspecifiedconditionsthroughcontactlensmaterialofunitthicknesswhensubjectedtounitpressuredifferenceNOTE1Oxygenpermeabilityisstatedintraditionalunitsof(cm2/s)[mlO2/(mlmmHg)],whichisequivalentto(cm3O2cm)/(cm2smmHg).Theunitsare(cm2/s)[mlO2/(mlhPa)],or(cm3O2cm)/(cm2shPa)whenthehectopascal(hPa)isusedinsteadofmmHg.ToexpressDkunitsintermsofhPainsteadofmmHg,multiplyDkmagnitudesusingmmHginthedenominatorby0,75006.ToexpressDkunitsintermsofmmHginsteadofhectopascals,multiplyDkmagnitudesusinghectopascalsinthedenominatorby1,33322.NOTE2Intermsofmeasurementusingthecoulometricmethod,Dkisequaltotheoxygentransmissibility(Dk/t)multipliedbythesamplethickness(t).Oxygenpermeabilityisaphysicalpropertyofthematerialandisnotafunctionoftheshapeorthicknessofthematerialsample.3.3oxygentransmissibilityDk/toxygenpermeabilitydividedbythethickness(t),incentimetres,ofthemeasuredsampleunderspecifiedconditionsNOTE1Oxygentransmissibilityisstatedintraditionalunitsof(cm/s)[mlO2/(mlmmHg)],whichisequivalentto(cm3O2)/(cm2smmHg).Theunitsare(cm/s)[mlO2/(mlhPa)],or(cm3O2)/(cm2shPa)whenthehectopascal(hPa)isusedinsteadofmmHg.ToexpressDk/tunitsintermsofhPainsteadofmmHg,multiplyDk/tmagnitudesusingmmHginthedenominatorby0,75006.ToexpressDk/tunitsintermsofmmHginsteadofhectopascals,multiplyDk/tmagnitudesusinghectopascalsinthedenominatorby1,33322.NOTE2Intermsofmeasurementusingthecoulometricmethod,Dk/tisequaltotheoxygenflux(j)dividedbythedifferenceinoxygentension(partialpressureofoxygen)betweenatmospheresatthetwoexposedsurfacesofthesamplecontactlens.Oxygentransmissibilityisapropertyofthelensmaterialandlensthickness;itdependsonthedesignofthecontactlens.3.4thicknesstradialthicknesswithinthecentralareaofthetestsample,asmeasuredaccordingtoISO9339-1,ortheharmonicmeanthicknessoftheareaoftestsampleexposedtooxygenflowNOTETobeconsistentwithotherdefinitionsandequationsinthispartofISO9913,tshouldbeexpressedincentimetres(cm).SIST EN ISO 9913-2:2001

ISO9913-2:2000(E)©ISO2000–Allrightsreserved33.5harmonicmeanthicknesstHMrotationallysymmetriccontactlensthatthicknesscalculatedfromaseriesof(h+1)radialthicknessmeasurementsatintervalsofequalannularareafromthecentre(point0)totheedge(pointh)ofthecircularareaexposedtooxygenflowSee6.1.1b).NOTETheintervalbetweenthicknessmeasurements1shouldalloweachsuccessiveannulustobeofthesamearea:thtttttHMh.+1111110123(1)wheretHMistheharmonicmeanthicknessofrotationallysymmetrictestsample,incentimetres;t0tothareradialthicknessesmeasuredorcalculatedatintervalsofequalareafromthecentre(t0)totheedge(th)oftheexposedsamplearea,incentimetres.4Principle4.1OverviewArigidornon-hydrogelflexiblecontactlensisplacedintheapparatusdescribedin6.1,withexposedfrontandrearcontactlenssurfaceareasincontactwithgasmixturesateyetemperature(35°C).Thegaseousenvironmentsattheanteriorandposteriorcontactlenssurfacesareseparatedbythecontactlens,whichactsasabarriertothenetflowofoxygenfromtheanteriorenvironmenttotheposteriorenvironment.Thetwoenvironmentsandthecontactlenscanbepurgedofalldetectableoxygengas.Oncepurged,anoxygen-containinggasisallowedtofilltheanteriorenvironmentalchamberandtodiffusethroughthecontactlens.Aninertcarriergas,initiallyoxygen-free,isallowedtoflowacrosstheposteriorenvironmentalchamberattheposteriorcontactlenssurfaceandtoremoveoxygenmoleculesthathavecrossedthecontactlensbarrier.Thecarriergas,nowcontainingasmallconcentrationofoxygen,isdirectedtoacoulometricsensorwhichcreatesacurrentproportionaltotheconcentrationofoxygenflowingpastthedetector.Withappropriateinstrumentcalibration,suchthattheconcentrationofoxygenatthedetectorispreciselyknown,therateofoxygenflowqVinmicrolitrespersecond,pastthedetectorcanbedeterminedandrecorded.4.2CalculatedvaluesOxygenflux(j),oxygentransmissibility(Dk/t),andoxygenpermeability(Dk)canbederivedbyusingequation(2),knowingtheareaofthecontactlensthroughwhichoxygenhaspassed(A,insquarecentimetres),thethicknessofthecontactlensorsample(t),thecalculatedoxygenflux(j)orrecordedrateofoxygenflowpastthedetectorqV,andtheoxygenpressuredifferencebetweenanteriorandposteriorenvironmentalchambersduringmeasurement(PA–PP,inhectopascals,wherePisapproximately116hPaandPPisassumedtobezero).DktqPAVA3ml10l(2)1FattI.,RubenC.M.J.Br.Cont.LensAssoc.,17(4),1994,pp.115ff.SIST EN ISO 9913-2:2001

ISO9913-2:2000(E)4©ISO2000–AllrightsreservedwhereDkistheoxygenpermeabilityoftestsample,in(cm2/s)[mlO2/(mlhPa)];PAisthe(barometricpressurevapourpressure)(0,209),expressedinhectopascals;tisthethicknessoftestsample(measured),expressedincentimetres;Aistheexposedareaoftestsample(measured),expressedinsquarecentimetres;qVistherateofoxygenflowpastthedetector(measured),expressedinmicrolitrespersecond;0,209istheoxygenfractionintheoxygenatedtestgas(ifotherthan0,209,thatvalueisused).4.3PrecisionofmeasurementAsingledeterminationofoxygentransmissiblity(Dk/t)and/oroxygenpermeability(Dk)shallhaveareproducibilityvalue(R)of10%ofthecorrectedvalue,inaccordancewithISO5725.5Reagentsandmaterials5.1Oxygen-freecarriergas,consistingofnitrogengas(volumefraction99,9%ormore)oramixtureofnitrogengas(volumefraction97%to99,5%)andhydrogengas(volumefraction0,5%to3%).Thecarriergasshallbedryandcontainnotmorethanavolumefractionof0,01%ofoxygen.Anoxygentrapandamoisturetrapshallensurethatthecarriergasisessentiallyoxygen-freeanddrypriortoreachingthediffusioncell(6.1.1)andthatvapourpressurePPiszero.5.2Oxygenatedtestgas,comprisingeitheramixtureofoxygengas(volumefraction20,9%)andnitrogengas(volumefraction79,1%),orcompressedair,oroxygengas(volumefraction99,9%orgreater).Amoisturetrapdriesthetestgaspriortointroductionintotheanteriorenvironmentalchamberofthediffusioncell(6.1.1).5.3Sealinggrease,eitherahigh-viscositynon-siliconestopcockgreaseorahigh-vacuumgreasewhichisnearlyimpermeabletooxygen.A"sealinggrease"isrequiredforsealingthecontactlenstestsampletothetwohalvesofthediffusioncell,asnotedin6.1.1.5.4Standardreferencematerial(SRM),comprisinganon-hydrogelflatplasticfilm,typicallyusedforpreliminarycalibrationoftheapparatus,havingparallelsurfacesandacertifiedoxygentransmissibility(Dk/t)2.6Apparatus6.1Oxygengastransmissionapparatus,depictedinFigure1,consistingofadiffusioncell(6.1.1),O-ring,heatingunit(6.1.2),flowmeter,coulometricoxygensensor(6.1.3),loadresistorandrecorder(6.1.4).2SRM1470,areferencematerialusefulforcalibrationwithrespecttotestingofcontactlenses,hasacertifiedoxygentransmissibilityequalto0,07210–90,0004510–9(cm3O2)/(cm2smmHg)andisavailablefromtheNationalInstituteforStandardsandTechnology,Gaithersburg,Maryland,USA20899.Aseriesofsixrigidnon-hydrogelcontactlensreferencematerialsmaybeobtainedfromthecustodianofthePermeabilityReferenceMaterialRepository.Thematerialsareavailableintheformofcontactlensbuttonsfromsinglelots,andcanbelathedandpolishedtotheappropriatespecificationsasreferencesamplesforthepolarographicandcoulometricmethods.ThecustodianofrepositoryreferencebuttonsispresentlyDr.WilliamJ.Benjamin,Universityof
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