<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-01-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001410939</issuerCik>
        <issuerName>Ophthotech Corp.</issuerName>
        <issuerTradingSymbol>OPHT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001456590</rptOwnerCik>
            <rptOwnerName>Versant Venture Capital IV, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE SANSOME STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3630</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94104</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001456591</rptOwnerCik>
            <rptOwnerName>Versant Side Fund IV, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE SANSOME STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3630</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94104</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001456589</rptOwnerCik>
            <rptOwnerName>Versant Ventures IV, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE SANSOME STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3630</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94104</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-01-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>129709</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.2984</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5142333</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-01-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>817</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.2984</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>32394</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On January 14, 2019, the Reporting Persons received an additional 130,526 shares of Ophthotech Corporation (&quot;Ophthotech&quot;) common stock as a result of the post-closing adjustment as provided for in that certain Agreement and Plan of Merger dated October 30, 2018, by and among Ophthotech, Inception 4, Inc. and the other parties thereto.  No additional consideration was paid for such shares. The Reporting Persons' right to receive additional shares became fixed and irrevocable on October 30, 2018, the effective date of the merger.</footnote>
        <footnote id="F2">This report on Form 4 is jointly filed by Versant Venture Capital IV, L.P. (&quot;VVC IV&quot;) and Versant Side Fund IV, L.P. (&quot;VSF IV&quot;). Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein, except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that any such entity is a beneficial owner of such securities for the purpose of Section 16 or for any other purpose.</footnote>
        <footnote id="F3">These securities are held of record by VVC IV. Versant Ventures IV, LLC (&quot;VV IV&quot;) is the sole general partner of VVC IV and may be deemed to have voting and investment power over the securities held by VVC IV and as a result may be deemed to have beneficial ownership over such securities. Brian G. Atwood, Samuel D. Colella, Ross A. Jaffe, William J. Link, Rebecca B. Robertson, Bradley Bolzon, Ph.D., Charles M. Warden, Kirk G. Nielsen, Thomas Woiwode and Robin L. Praeger are managing directors of VV IV and share voting and dispositive power over the shares held by VVC IV; however, they each disclaim beneficial ownership of such securities, except to the extent of their pecuniary interests therein.</footnote>
        <footnote id="F4">These securities are held of record by VSF IV. VV IV is the sole general partner of VSF IV and may be deemed to have voting and investment power over the securities held by VSF IV and as a result may be deemed to have beneficial ownership over such securities. Brian G. Atwood, Samuel D. Colella, Ross A. Jaffe, William J. Link, Rebecca B. Robertson, Bradley Bolzon, Ph.D., Charles M. Warden, Kirk G. Nielsen, Thomas Woiwode and Robin L. Praeger are managing directors of VV IV and share voting and dispositive power over the shares held by VSF IV; however, they each disclaim beneficial ownership of such securities, except to the extent of their pecuniary interests therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Robin L. Praeger, Managing Director of Versant Ventures IV, LLC, general partner of Versant Venture Capital IV, L.P.</signatureName>
        <signatureDate>2019-01-16</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Robin L. Praeger, Managing Director of Versant Ventures IV, LLC, general partner of Versant Side Fund IV, L.P.</signatureName>
        <signatureDate>2019-01-16</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Robin L. Praeger, Managing Director of Versant Ventures IV, LLC</signatureName>
        <signatureDate>2019-01-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
