<PAGE>
                                                                   EXHIBIT 10.12

                      PATENT LICENSE AND ROYALTY AGREEMENT

     THIS AGREEMENT (the "Agreement") is made by and between OccuLogix, Inc.
(formerly Vascular Sciences Corporation), a Delaware Corporation (the
"Licensee"), and Dr. Hans Stock ("Stock") living in Germany, and the assignee of
the rights of Prof. Dr. Helmut Borberg ("Borberg"), listed as inventor along
with Dr. Richard Brunner ("Brunner") in US patent application 09/000,917, which
is the parent application of US letters patent 6,245,038 issued June 12, 2001
(the "Patent").

     WHEREAS, Brunner executed a patent license and royalty agreement with a
predecessor of the Licensee as of May 6, 2002 and amended and restated that
agreement as of the date hereof;

     WHEREAS, Borberg assigned all his right, title and interest to the Patent
and the Patent Rights to Stock;

     WHEREAS, Stock originally licensed any and all of his rights, title and
interests to the Patent and the Patent Rights to the Licensee in an undocumented
oral agreement;

     WHEREAS, Stock continues to desire to license any and all of his rights,
title and interest to the Patent and the Patent Rights derived therefrom to
Licensee, and

     WHEREAS, Licensee continues to desire to obtain an exclusive license to all
of Stock's interest in the Patent and the Patent Rights derived therefrom and to
exclusively own the License to any and all of his rights, title, interests and
ownership to the Patent and any and all related patents, rights and inventions
that specifically relate to the Patent whether owned now or at any time in the
future by Stock (the "License"), and

     WHEREAS, Stock shall be eligible to receive any and all consideration and
compensation from the Licensee, such as those pledged to be made by the Licensee
to Stock under the terms of this Agreement.

     NOW THEREFORE, in consideration for guaranteed Advance Royalty Payments and
Royalty Payments as described below, and other good and valuable consideration,
Stock does hereby continue to exclusively license, in accordance with the terms
set forth below, unto Licensee, its successors and assigns, Stock's entire
undivided right, title, ownership and interest in and to the Patent and the
invention(s) therein contained (the "Patent Rights"), throughout the Territory,
to be held and enjoyed by Licensee its successors and assigns, the same as it
would have been held and enjoyed by Stock if this Patent License and Royalty
Agreement had not been made and entered into.

     Stock recognizes that by signing this Agreement, the combination of this
Agreement and a patent license and royalty agreement between Brunner and
Licensee will collectively constitute an EXCLUSIVE PATENT LICENSE AND ROYALTY
AGREEMENT by which Stock and Brunner grant an exclusive license in the patent to
Licensee including the right to sue for past infringement.
<PAGE>
                                      -2-

1.  Patent Rights. Shall mean any and all of Stock's rights, title, ownership
    and interests in and to US letters patent 6,245,038 and any and all
    inventions, modifications, continuations-in-part, extensions, divisions,
    improvements, etc. made by Stock or his agents, in any and all areas that
    relate directly to the Patent, regardless of whether such inventions or
    improvements are patentable or may become patented; all inventions,
    modifications, continuations-in-part, extensions, divisions, improvements,
    etc. shall automatically be incorporated herein without the payment of any
    additional fees, royalties or any other compensation or considerations of
    any kind.

2.  Representation by Stock. Stock warrants that he as the assignee of the
    right of Borberg, along with Brunner, as the joint inventors of United
    States Patent 6,245,038, exclusively owns and possesses the Patent and the
    Patent Rights, and has all right and title thereto and that this Patent
    License and Royalty Agreement is made without encumbrance or threat of
    future interference by others claiming ownership therein and that no
    security interests to any third party exists therein or any other agreement
    the contrary.

3.  Representation by Licensee. Licensee represents that it is a bona fide
    corporation in good standing in Delaware.

4.  Advance Royalty Payments. Licensee agrees to pay Stock Fifty Thousand
    Dollars ($50,000 USD) annually as an advance and credited against any and
    all Royalty Payments paid in accordance with this Agreement. Such Advance
    Royalty Payments shall be paid to Stock and in equal payments of Twelve
    Thousand Five-hundred Dollars ($12,500 USD), made quarterly, on or before
    the expiration of Forty-five (45) days after the reporting close of each
    prior calendar quarter.

5.  Royalty Payments. Licensee agrees to pay royalties to Stock totaling
    One-and-a-Half Percent (1.5% in USD). Royalty Payments shall be calculated
    and paid based upon Total Net Revenues that Licensee receives from the bona
    fide commercial sales of its Products sold in reliance and dependence upon
    the validity of the Patient's claims and of the Patent Rights in the
    Territory.

6.  Accounting and Timing of Royalty Payments. Upon making each Royalty Payment,
    Licensee shall provide Stock with a summary of the accounting used to
    determine the amount of Royalty Payment due. Royalty Payments shall be made
    by wire transfer and shall be computed on Total Net Revenues received by the
    Licensee by the reporting close of each calendar quarter and distributed and
    paid to Stock and on a quarterly basis, on or before the expiration of
    Forty-five (45) days after the reporting close of each prior calendar
    quarter.

7.  Failure to Pay by Licensee. Should Licensee fail to make any payments as
    required herein, and should the Licensee fail to cure the breach created
    thereby, any and all rights, title and ownership to the License provided to
    the Licensee under this Agreement shall be forfeited and any and all such
    rights, title and ownership to the License shall, upon notice of the
    failure to cure the breach, immediately revert to Stock, and all monies paid
    by Licensee until such date shall be retained by him without forfeiture.
<PAGE>

                                     - 3 -

8.   Territory. Shall mean the United States and any other jurisdictions subject
     to recognizing any valid claims of the Patent or of the Patent Rights.

9.   Total Net Revenues. Shall mean total gross revenues less any discounts,
     rebates, shipping costs, handling costs, transportation insurance costs,
     importation fees, and duties on any and all Products sold by the Licensee
     in the Territory and which are sold in reliance upon and specifically used
     in accordance with or subject to any of the valid claims of the Patent.

10.  Records. Licensee agrees to keep complete and correct books, accounts and
     records according to Generally Accepted Accounting Principles (GAAP)
     regulations to facilitate computation of Royalty Payments. Stock or his
     representatives acceptable to Licensee, shall have a full right of
     accounting including the right to confidentially examine Licensee's books
     and records, at all reasonable times and upon reasonable notice, for the
     purpose of verifying the amount of Royalty Payments due.

11.  Products. Shall mean any of Licensee's products, goods or technologies sold
     unaffiliated third parties in the Territory for the purposes of providing
     extracorporeal therapies for the treatment of the ophthalmic diseases as
     defined by any valid claim(s) of the Patent, in this case, Licensee's sale
     of extracorporeal filters and tubing sets for use in any and all ophthalmic
     indications.

12.  Term. The Royalty Payments shall be due to Stock beginning with the first
     bona fide commercial sale of any Product in the Territory and may, at the
     discretion of Licensee terminate upon the first of any of the following
     three events to occur. (a) All patents of the Patent Rights expire; (b) All
     patent claims of the Patent Rights are invalidated; or (c) A similarly
     fashioned competitive extracorporeal product, method or technology is
     commercially introduced in the Territory for use in ophthalmic indications
     that could not be deterred by best-efforts enforcement/infringement
     proceedings brought by Licensee against the competitive product, method or
     technology where such proceedings are made in reliance in full or in part
     upon the Patent's claims and or the Patent Rights.

13.  Patent Defense. Licensee shall pay for any and all costs incurred for
     patent maintenance, enforcement and defense of the Patent or the Patent
     Rights in the Territory.

14.  Participation. Stock agrees, in consideration of the premises herein, that
     his executors and administrators will, at any time upon request,
     communicate to the Licensee, its successors and assigns, any facts relating
     to said Patent and Patent Rights, and the history thereof, known to him or
     his successors and assigns, and that he will testify as to the same in any
     interference or other proceeding when requested to do so by the Licensee,
     its successors and assigns. Any and all costs of such participation by
     Stock or his successors and assigns shall be borne by Licensee.

15.  Succession. Stock binds himself and his heirs, executors, administrators,
     employees and legal representatives, as the case may be, to execute and
     deliver to the Licensee, its successors and assigns, any further documents
     or instruments and to do any and all further acts that may be deemed
     necessary by the Licensee, its successors and assigns to
<PAGE>
                                      -4-

    file applications for improvements and inventions in any country where
    Licensee may elect to file such application(s), and that may be necessary
    to vest in the Licensee, its successors and assigns, the license, rights or
    title herein conveyed, or intended so to be, and to enable such title to be
    recorded in the United States and or foreign countries where such
    application(s) may be filed. Any and all costs of such participation by
    Stock or his successors and assigns shall be borne by Licensee.

16. Relationship of the Parties: Indemnification. It is agreed that this
    Agreement does not make any Party herein a general or special agent, legal
    representative, subsidiary, joint venturer, partner, employee or servant of
    any other Party herein for any purpose.

17. Breach and Disputes. Any breaching Party shall have Thirty (30) Days from
    the date of notification to cure such breach. Any dispute between the
    Parties to this Agreement shall be resolved through binding arbitration,
    which shall be governed under the rules and regulations of the American
    Arbitration Association.

18. Forum, Venue and Governing Law. This agreement shall be governed and
    interpreted under Delaware law (without applying its conflict of law
    principles). Exclusive venue for legal proceedings arising hereunder shall
    be in Hillsborough County, Florida.

19. Entire Agreement. This Agreement supersedes any prior understanding that
    may have been reached between the Parties (including the Consulting
    Agreement between OccuLogix Corporation and Hans Stock dated June 25, 2002)
    and encompasses the entire agreement between the Licensee and Stock with
    respect to the Patent and the Patent Rights. The terms of this Agreement are
    confidential and shall be maintained by the Parties in accordance thereby.

20. Modification. This Agreement cannot be modified except in writing executed
    mutually between the Parties.

          IN WITNESS WHEREOF, the Parties have signed and executed this
Agreement and have caused this Agreement to becomes effective as of the
Effective Date last executed below.

OCCULOGIX, INC.                                Dr. HANS STOCK


By:     /s/ Richard Davis                      By:  /s/ Dr. Hans Stock
    --------------------------                     --------------------


Title:
       -----------------------

Date:     August 6, 2004                       Date:   6. August 2004
      ------------------------                       ------------------