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  <xsd:element id="sght_RedeemablePreferredStockWarrantsLiabilitiesNonCurrent" name="RedeemablePreferredStockWarrantsLiabilitiesNonCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="sght_ReductionInCostOfRevenue" name="ReductionInCostOfRevenue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sght_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeitedInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeitedInPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantedInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantedInPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_StockIssuedDuringPeriodValueConversionOfConvertibleSecuritiesNetOfAdjustment" name="StockIssuedDuringPeriodValueConversionOfConvertibleSecuritiesNetOfAdjustment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="sght_TemporaryEquityIssuanceCost" name="TemporaryEquityIssuanceCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sght_TemporaryEquityIssuanceCosts" name="TemporaryEquityIssuanceCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sght_TemporaryEquityOriginalIssuancePricePerShare" name="TemporaryEquityOriginalIssuancePricePerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="sght_TemporaryEquityStockIssuedDuringPeriodSharesNewIssues" name="TemporaryEquityStockIssuedDuringPeriodSharesNewIssues" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_TotalBaseRentUnderLeaseAgreement" name="TotalBaseRentUnderLeaseAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sght_UnderwritingDiscountsAndCommission" name="UnderwritingDiscountsAndCommission" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sght_UnpaidInitialPublicOfferingCostsInAccountsPayableAndAccruedLiabilities" name="UnpaidInitialPublicOfferingCostsInAccountsPayableAndAccruedLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sght_WarrantsFairValue" name="WarrantsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="sght_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureLineItems" name="OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_CommonStockAvailableForFutureGrantMember" name="CommonStockAvailableForFutureGrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_CommonStockOptionsIssuedAndOutstandingMember" name="CommonStockOptionsIssuedAndOutstandingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_DryEyeMember" name="DryEyeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_FederalAndStateMember" name="FederalAndStateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_FundingOfTranche1AndTranche2UnderTwoThousandNineteenTermLoanMember" name="FundingOfTranche1AndTranche2UnderTwoThousandNineteenTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_FundingOfTwoThousandNineteenTermLoanTranche3Member" name="FundingOfTwoThousandNineteenTermLoanTranche3Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_MidCapFinancialServicesMember" name="MidCapFinancialServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_PaycheckProtectionProgramLoanMember" name="PaycheckProtectionProgramLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_RedeemableConvertiblePreferredStockAndWarrantsMember" name="RedeemableConvertiblePreferredStockAndWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_RedeemableConvertiblePreferredStockWarrantsMember" name="RedeemableConvertiblePreferredStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_RestrictedStockUnitsOutstandingMember" name="RestrictedStockUnitsOutstandingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_RevolvingCreditFacilityTwoThousandNineteenMember" name="RevolvingCreditFacilityTwoThousandNineteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_RevolvingCreditFacilityTwoThousandTwentyMember" name="RevolvingCreditFacilityTwoThousandTwentyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SeniorSecuredTwentyTwentyTermLoanMember" name="SeniorSecuredTwentyTwentyTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SeniorSecuredTwoThousandNineteenTermLoanMember" name="SeniorSecuredTwoThousandNineteenTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SeriesARedeemableConvertiblePreferredStockMember" name="SeriesARedeemableConvertiblePreferredStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SeriesCRedeemableConvertiblePreferredStockMember" name="SeriesCRedeemableConvertiblePreferredStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SeriesERedeemableConvertiblePreferredStockMember" name="SeriesERedeemableConvertiblePreferredStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SeriesFRedeemableConvertiblePreferredStockMember" name="SeriesFRedeemableConvertiblePreferredStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SharesAvailableForFuturePurchaseUnderESPPMember" name="SharesAvailableForFuturePurchaseUnderESPPMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_SurgicalGlaucomaMember" name="SurgicalGlaucomaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TermLoanMember" name="TermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TrancheOneAndTwoLoansMember" name="TrancheOneAndTwoLoansMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TrancheOneLoansMember" name="TrancheOneLoansMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TrancheThreeLoansMember" name="TrancheThreeLoansMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TrancheTwoLoansMember" name="TrancheTwoLoansMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TwentyTwentyMidcapCreditFacilityMember" name="TwentyTwentyMidcapCreditFacilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TwoThousandAndElevenPlanMember" name="TwoThousandAndElevenPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TwoThousandAndTwentyOnePlanMember" name="TwoThousandAndTwentyOnePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TwoThousandNineteenWarrantsMember" name="TwoThousandNineteenWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TwoThousandTwentyOneEmployeeStockPurchasePlanMember" name="TwoThousandTwentyOneEmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TwoThousandTwentyTermLoanMember" name="TwoThousandTwentyTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_TwoThousandTwentyWarrantsMember" name="TwoThousandTwentyWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTable" name="OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sght_AccountingForPayrollProtectionProgramPolicyTextBlock" name="AccountingForPayrollProtectionProgramPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_AccruedAndOtherCurrentLiabilitiesTableTextBlock" name="AccruedAndOtherCurrentLiabilitiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_CommonStockWarrantPolicyTextBlock" name="CommonStockWarrantPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_CommonStockWarrantsTextBlock" name="CommonStockWarrantsTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_ConcentrationOfCreditRiskPoliciesTextBlock" name="ConcentrationOfCreditRiskPoliciesTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_CostOfGoodsSoldPolicyTextBlock" name="CostOfGoodsSoldPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_CurrencyRemeasurementPolicyTextBlock" name="CurrencyRemeasurementPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_DeferredOfferingCostsPolicyTextBlock" name="DeferredOfferingCostsPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_EmergingGrowthCompanyPolicyTextBlock" name="EmergingGrowthCompanyPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_ReconciliationOfTheStatutoryFederalIncomeTaxRateTableTextBlock" name="ReconciliationOfTheStatutoryFederalIncomeTaxRateTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_RedeemableConvertiblePreferredStockIssuedAndOutstandingTableTextBlock" name="RedeemableConvertiblePreferredStockIssuedAndOutstandingTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_RedeemableConvertiblePreferredStockTextBlock" name="RedeemableConvertiblePreferredStockTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_RedeemableConvertiblePreferredStockWarrantsPolicyTextBlock" name="RedeemableConvertiblePreferredStockWarrantsPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sght_WarrantDisclosureTextBlock" name="WarrantDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
