**NEITHER
        THIS NOTE NOR ANY SECURITIES THAT MAY BE ISSUED UPON CONVERSION HEREOF HAVE
        BEEN
        REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR REGISTERED OR
        QUALIFIED UNDER ANY STATE SECURITIES LAWS. THIS NOTE AND ANY SUCH SECURITIES
        MAY
        NOT BE TRANSFERRED UNLESS SO REGISTERED AND QUALIFIED UNDER ALL APPLICABLE
        SECURITIES LAWS, OR UNLESS SUCH REGISTRATION AND QUALIFICATION ARE NOT
        REQUIRED.**
  
  **CONVERTIBLE
        UNSECURED PROMISSORY NOTE**
  $2,000,000.00 April
        4,
        2006
  FOR
        VALUE
        RECEIVED, the undersigned, **Solx,
        Inc.** ,
        a
        Delaware corporation (the “ Company ”),
        hereby promises to pay to **OccuLogix,
        Inc.** ,
        a
        Delaware corporation, or its assigns (“ OccuLogix ”),
        at
        the times set forth below and subject to acceleration or conversion as set
        forth
        herein, the aggregate principal amount of TWO MILLION DOLLARS ($2,000,000.00)
        (the “ Principal
        Amount ”),
        and
        interest on the unpaid Principal Amount, from time to time outstanding, which
        shall accrue on a daily basis from the date on which the Principal Amount
        has
        been loaned to the Company through and including the date on which such
        Principal Amount is paid in full (or the Principal Amount and accrued interest
        is converted into Conversion Shares (defined below) in accordance with Section
        3
        hereof), at an annual interest rate equal to the “Prime Rate” as announced from
        time to time by Bank of America, N.A., or its successor, plus two percent
        (2%).
        Unless the indebtedness evidenced by this Convertible Unsecured Promissory
        Note
        (this “ Note ”)
        becomes due and payable earlier as provided in Section 4 below, or is converted
        into Conversion Shares in accordance with Section 3.2 below, the Principal
        Amount then outstanding, and any interest accrued but unpaid thereon, shall
        be
        paid in one (1) payment in lawful money of the United States of America,
        on
        October 2, 2006 (the “Maturity Date”).
  **1.** 
Defined
        Terms .
        For
        purposes of this Note, the terms listed below shall have the respective meanings
        set forth below:
  **1.1**  “ Amended  and  Restated  Stockholders  Agreement ”
means
        the Amended and Restated Stockholders Agreement, dated as of June 17, 2004,
        by
        and among the Company, Boston Scientific Corporation, and the stockholders
        listed on Exhibit A thereto, as such agreement may be amended, restated,
        supplemented or replaced from time to time;
  **1.2**  “ BSX  Note ”
means
        the Convertible Secured Promissory Note dated December 2005, in the principal
        amount of $1,000,000, granted by the Company in favor of Boston Scientific
        Corporation;
  **1.3**  “ business
        day ”
        means any day
        that banks located in Boston, Massachusetts are open for business ( *i.e.* ,
        not
        Saturdays, Sundays or legal holidays for such banks);
  **1.4**  “ Common
        Stock ”
means
        the common stock, $.001 par value, of the Company;
  **1.5**  “ Conversion
        Shares ”
means,
        in the case of any conversion pursuant to Section 3.2 below, shares of the
        Company’s Common Stock;
  **1.6**  “ Due  Diligence  Period ”
means
        the time period between March 27, 2006 through and including May 15, 2006
        or
        such other date as the Company and OccuLogix may mutually agree;
  **1.7**  “ Fully  Diluted  Basis ”
means
        to take into account all issued and outstanding shares of Common Stock and
        all
        issued and outstanding shares of preferred stock of the Company on an
        as-converted basis at their respective conversion prices then in
        effect;
  **1.8**  “ Material
        Adverse Effect ”
        means any
        change or effect that, when taken individually or together with all other
        adverse changes or effects, is or is reasonably likely to be materially adverse
        to the business, results of operations or financial condition of the Company,
        taken as a whole;
  **1.9**  “ OccuLogix  Transaction ”
means
        the purchase of 100% of the issued and outstanding shares of the capital
        stock
        of the Company contemplated in that Letter of Intent between the Company
        and
        OccuLogix dated March 26, 2006 (the “Letter Agreement”) or the acquisition of
        the Company by OccuLogix or any of its affiliates by merger, consolidation
        or
        otherwise;
  **1.10**  “ Post-Conversion  Agreement ”
has
        the
        meaning attributed to such term in Section 3.3;
  **1.11**  “ Sale
        of the Company ”
means
        (i) during the Due Diligence Period, any agreement, agreement in principle
        or
        other commitment (whether or not legally binding or written or oral) relating
        to
        a sale of the Company in a single or related series of transactions, whether
        by
        merger, consolidation or other transaction (including, without limitation,
        the
        sale of outstanding shares of the capital stock of the Company) in which,
        in
        each case, the holders of the Company’s voting securities outstanding
        immediately prior to the consummation of the transaction or transactions
        own
        securities with less than a majority of the voting power of the Company or
        a
        successor immediately after the transaction (a “Change in Voting Control”), or
        by sale or license of all or substantially all of the Company’s assets, or
        otherwise (a “Competing Transaction”) or (ii) during the Due Diligence Period
        and for a three-month period following the end of the Due Diligence Period,
        the
        consummation of a Competing Transaction; provided, however, that if the
        consummation of a Competing Transaction occurs during the three-month period
        after the Due Diligence Period, then such Competing Transaction shall only
        be a
        Sale of the Company if any discussion regarding such Competing Transaction
        was
        initiated by the Company, or any step in furtherance of it was taken by the
        Company, during the Due Diligence Period. For clarification, the OccuLogix
        Transaction, if consummated, shall not be considered a Sale of the Company.
        For
        further clarification, any offering by the Company of shares of its capital
        stock in exchange for cash in which a Change of Voting Control does not occur,
        shall not be considered a Sale of the Company.
  **2.**           
         Payment. Payment of interest and principal hereunder shall be made
        at the business address of the holder hereof. All computations of interest
        payable under this Note shall be made on the basis of the actual number of
        calendar days elapsed. All payments hereunder shall be applied first to
        any unpaid accrued interest, second to payment of all, if any, other
        amounts except principal due under or in respect of this Note, and third
        to repayment of the unpaid Principal Amount.
  **3.**    Cancellation; Conversion. This Note shall be
        cancelled or convertible as follows:
  **3.1**  Cancellation
        Upon OccuLogix Transaction. Notwithstanding anything else to the contrary in
        this Note, this Note and all outstanding obligations and amounts owing by
        the
        Company under this Note shall automatically (without any action by any party)
        be
        cancelled upon the consummation of the OccuLogix Transaction, unless OccuLogix
        should otherwise decide that this Note shall not be cancelled.
  **3.2**  Conversion
        Upon a Sale of the Company, etc .
        At the
        sole option of OccuLogix, this Note may be converted immediately upon (with
        such
        conversion made contingent upon) (a) a Sale of the Company, (b) a breach
        by the
        Company of its exclusivity covenant in paragraph 8 of the Letter Agreement,
        (c)
        the Principal Amount remaining outstanding and owing after the Maturity Date,
        or
        (d) the occurrence of an Event of Default as set forth in Section 4 below,
        into
        that number of Conversion Shares as shall be equal to 10% of the issued and
        outstanding capital stock of the Company on a Fully Diluted Basis. The Company
        shall give OccuLogix written notice fifteen (15) business days prior to the
        consummation of any Sale of the Company, which notice shall describe in
        sufficient detail the terms of such transaction, to enable OccuLogix to make
        a
        decision as to whether to exercise its option under this Section 3.2.
        Notwithstanding the foregoing, in the event of a failure to reach a definitive
        agreement during the Due Diligence Period in connection with the OccuLogix
        Transaction due to (i) bad faith negotiations on the part of OccuLogix, or
        (ii)
        a decision by OccuLogix that is not due or caused by either the bad faith
        negotiations of the Company or otherwise by any liability or adverse condition
        of the Company not disclosed to OccuLogix on or prior to the date hereof,
        which
        liability or adverse condition would have a Material Adverse Effect, OccuLogix
        shall be entitled to exercise its option to convert the Note only after the
        end
        of the 90-day period following the Maturity Date, provided that any Principal
        Amount or any accrued but unpaid interest thereon remains
        outstanding.
  **3.3**  Manner
        of Conversion .
        Subject
        to the restriction on OccuLogix’s right to convert this Note in the event of a
        failure to reach a definitive agreement during the Due Diligence Period,
        OccuLogix shall be deemed to be the holder of the Conversion Shares: (a)
        in
        connection with a conversion pursuant to Section 3.2, immediately upon (and
        contingent upon) the consummation of a Sale of the Company, provided that
        OccuLogix has provided the Company with written notice of conversion prior
        to
        the consummation of the Sale of the Company as provided in Section 3.2 above;
        (b) in connection with the breach by the Company of its exclusivity covenant
        in
        paragraph 8 of the Letter Agreement, immediately upon (and contingent upon)
        the
        independent determination of a third party arbitrator, or other competent
        decisionmaker mutually acceptable to the Company and OccuLogix, acting
        reasonably, conducted in accordance with procedures mutually acceptable to
        the
        Company and OccuLogix, acting reasonably; (c) in the event that the Principal
        Amount remains outstanding and owing after the Maturity Date, immediately
        upon
        (and contingent upon) the expiration of the cure period after receipt of
        notice
        as set forth in Section 4(d) below and provided that OccuLogix has delivered
        a
        notice to the Company of its intention to convert this Note pursuant to Section
        3.2; and (d) in connection with an Event of Default, immediately upon (and
        contingent upon) the expiration of the applicable cure period after receipt
        of
        notice as set forth in Section 4 below. At such time, OccuLogix shall have
        all
        of the rights of a holder of Common Stock and, upon its request, shall be
        entitled to receive a certificate representing the Conversion Shares into
        which
        this Note converts. Upon conversion of the Principal Amount and accrued but
        unpaid interest on this Note into Conversion Shares as provided herein, the
        provisions of this Note relating to the obligation of the Company to pay
        principal and interest to OccuLogix, set forth herein, shall be null and
        void
        and no payment of principal and interest shall be owed or paid by the Company
        to
        OccuLogix pursuant to this Note. However, subject to the foregoing, this
        Note
        shall remain in full force and effect until such time as the Company and
        OccuLogix enter into a separate agreement that shall provide OccuLogix with
        protection substantially equivalent to the protection provided to OccuLogix
        hereunder, including, without limitation, the anti-dilutive protection
        contemplated in Section 3.4 (the “Post-Conversion Agreement”). The Company and
        OccuLogix shall use best efforts to negotiate, execute and deliver the
        Post-Conversion Agreement as soon as practicable following the conversion
        of
        this Note but, in any event, by no later than the end of the 45-day period
        following the conversion of this Note, subject to any mutually agreed extension
        of time. If the Post-Conversion Agreement is not entered into within such
        45-day
        period or other agreed time period, then the provisions of Section 3.4 below
        of
        this Note shall continue in full force and effect.
  **3.4**  Continuing
        Equity Ownership .
        Until
        the earlier of (i) any merger or consolidation which results in the voting
        securities of the Company outstanding immediately prior thereto representing
        immediately thereafter (either by remaining outstanding or by being converted
        into voting securities of the surviving or acquiring entity) less than a
        majority of the combined voting power of the voting securities of the Company
        or
        such surviving or acquiring entity outstanding immediately after such merger
        or
        consolidation or any sale of all or substantially all of the assets of the
        Company, in each case, with a pre-transaction valuation of the Company equal
        to
        or greater than $5,000,000.00, and (ii) an underwritten public offering of
        shares of common stock of the Company at a pre-offering valuation of the
        Company
        greater than $5,000,000.00 and net proceeds to the Company of at least
        $1,000,000.00, from time to time, following the conversion of this Note pursuant
        to Section 3.2, the Company shall issue to OccuLogix, without payment of
        additional consideration by OccuLogix, such number of additional shares of
        Common Stock as shall be necessary for OccuLogix always to maintain an ownership
        percentage in the Company equal to 10% of the issued and outstanding capital
        stock of the Company on a Fully Diluted Basis.
  **4.**           
        Acceleration. At OccuLogix’s option, the entire unpaid portion of the
        Principal Amount and all accrued but unpaid interest represented by this
        Note
        will become due and payable upon written notice of acceleration given by
        OccuLogix to the Company immediately prior to or following any of the following
        (each, an “Event of Default”) (a) liquidation or dissolution of the
        Company, or any other termination or winding-up of its existence or business,
        (b) appointment of any receiver for the Company or its assets,
        (c) assignment by the Company for the benefit of its creditors, (d)
        material breach by the Company of this Note that is not cured within thirty
        (30)
        days’ written notice thereof from OccuLogix, in the case of any defaults other
        than payment defaults, or two (2) days’ written notice thereof from OccuLogix,
        in the case of any payment defaults, (e) institution by the Company of
        insolvency, receivership or bankruptcy proceedings or any other proceedings
        for
        the settlement of a party’s debts, change of control of the Company or Sale of
        the Company, or if any such proceeding shall be filed or shall be commenced
        against the Company by a third party and the Company shall indicate its approval
        thereof, consent thereto or acquiescence therein or such proceeding shall
        not
        have been dismissed within sixty (60) days following the filing thereof,
        (f) an
        event of default under any mortgage, indenture, obligation, instrument or
        indebtedness of the Company, which default results in $50,000 or more (in
        the
        aggregate) of such indebtedness to become due and payable by the Company
        prior
        to its stated maturity date, or (g) a Sale of the Company. A breach by the
        Company of the representation and warranty contained in Section 5.3 shall
        be
        considered a material breach of this Note.
  **5.**            
        Representations and Warranties of the Company .
        The
        Company hereby represents and warrants to OccuLogix as follows:
  **5.1**  Organization,
        Good Standing and Qualification .
        The
        Company is a corporation duly organized, validly existing and in good standing
        under the laws of the State of Delaware and has all requisite corporate power
        and authority to carry on its business as now conducted. The Company is duly
        qualified to transact business and is in good standing in each jurisdiction
        in
        which the failure to so qualify would have a Material Adverse Effect. The
        Company has all requisite corporate power and authority to own and operate
        its
        properties and assets, to issue this Note and the Conversion Shares, and
        to
        perform its obligations under, and carry out the provisions of, this
        Note.
  **5.2**  Authorization;
        Binding Obligations; Governmental Consents .
  (a)  All
        corporate action on the part of the Company, its officers, directors and
        stockholders necessary for the authorization, execution and issuance of this
        Note, and the performance of all obligations of the Company hereunder, have
        been
        taken prior to the date hereof. This Note is a valid and legally binding
        obligation of the Company, enforceable in accordance with its terms, except
        (i)
        as limited by applicable bankruptcy, insolvency, reorganization, moratorium,
        and
        other laws of general application affecting enforcement of creditors’ rights,
        and (ii) as limited by laws relating to the availability of specific
        performance, injunctive relief, or other equitable remedies.
  (b)    
        No consent, approval, permit, order or authorization of, or registration,
        qualification, designation, declaration or filing with, any federal, state
        or
        local governmental authority on the part of the Company is required in
        connection with the execution and issuance of this Note.
  **5.3**  Compliance
        with Other Instruments .
        The
        Company is not in violation or default of any provision of its certificate
        of
        incorporation or by-laws or similar organizational documents, or of any
        mortgage, indenture, contract, agreement, instrument, judgment, order, writ,
        decree or contract to which it is a party or by which it is bound or, to
        the
        best of Company’s knowledge, of any provision of any federal or state statute,
        rule or regulation applicable to the Company, which violation or default
        could
        reasonably be expected to have a Material Adverse Effect. The issuance of
        this
        Note and the Conversion Shares will not result in any such violation or be
        in
        conflict with or constitute, with or without the passage of time or giving
        of
        notice, either a default under any such provision, instrument, judgment,
        order,
        writ, decree or material contract, or result in the creation of any mortgage,
        pledge, lien, charge or encumbrance upon any of the properties or assets
        of the
        Company or the suspension, revocation, impairment, forfeiture, or nonrenewal
        of
        any permit, license, authorization, or approval applicable to the business,
        or
        operations or any of the assets or properties the Company.
  **5.4**  Valid
        Issuance .
        The
        Conversion Shares to be issued sold and delivered upon conversion of this
        Note,
        in accordance with the terms hereof and for the consideration expressed herein,
        will be duly and validly issued, fully paid and nonassessable. Any shares
        of
        Common Stock issuable upon conversion of such Conversion Shares, in accordance
        with the terms of thereof, will be duly and validly issued, fully paid and
        nonassessable.
  **5.5**  Seniority
        of Note .
        Until
        cancellation or conversion as provided for in this Note, after the Maturity
        Date
        (or earlier upon and as of an Event of Default), this Note shall be senior
        to
        all other debt obligations of the Company evidenced by any loan agreement,
        note
        or other instrument of any similar kind, and, after the Maturity Date (or
        earlier upon and as of an Event of Default), no payment(s) shall be made
        under
        any such other debt obligations until OccuLogix has received payment in full
        of
        the Principal Amount.
  **5.6**  Current
        Liabilities .
        The
        current liabilities of the Company as of March 28, 2006 do not exceed
        $2,500,000.00.
  **6.**            
        Representations and Warranties of OccuLogix. OccuLogix hereby represents
        and warrants to the Company as follows:
  **6.1**  Organization .
        OccuLogix is a corporation duly organized, validly existing and in good standing
        under the laws of the State of Delaware and has all requisite corporate power
        and authority to carry on its business as now conducted. OccuLogix has all
        requisite corporate power and authority to perform its obligations under,
        and
        carry out the provisions of, this Note.
  **6.2**  Authorization;
        Binding Obligations; Governmental Consents .
  (a) All
        corporate action on the part of OccuLogix, its officers, directors and
        stockholders necessary for the performance of all obligations of OccuLogix
        hereunder, have been taken prior to the date hereof. This Note is a valid
        and
        legally binding obligation of OccuLogix, enforceable in accordance with its
        terms, except (i) as limited by applicable bankruptcy, insolvency,
        reorganization, moratorium, and other laws of general application affecting
        enforcement of creditors’ rights, and (ii) as limited by laws relating to the
        availability of specific performance, injunctive relief, or other equitable
        remedies.
  (b) No
        consent, approval, permit, order or authorization of, or registration,
        qualification, designation, declaration or filing with, any federal, state
        or
        local governmental authority on the part of OccuLogix is required in connection
        with the execution and issuance of this Note.
  **6.3**  Investment
        Representations .
        OccuLogix understands that neither this Note nor the Conversion Shares have
        been
        registered under the Securities Act of 1933, as amended (the “ Securities
        Act ”).
        OccuLogix also understands that this Note and the Conversion Shares are being
        offered and sold pursuant to an exemption from registration contained in
        the
        Securities Act based in part upon OccuLogix’s representations contained in this
        Note. OccuLogix hereby represents and warrants as follows:
  (a) *Acquisition
        for Own Account* .
        OccuLogix is acquiring this Note and the Conversion Shares for OccuLogix’s own
        account for investment only, and not with a view toward their
        distribution.
  (b) *Accredited
        Investor* .
        OccuLogix represents that it is an “accredited investor” within the meaning of
        Regulation D under the Securities Act.
  **7.**            
        Affirmative Covenants. Unless OccuLogix shall otherwise agree in writing,
        the Company covenants and agrees that, so long as this Note is
        outstanding:
  **7.1**  Punctual
        Payment . The
        Company will duly and punctually pay or cause to be paid the Principal Amount
        and interest under this Note and all other amounts provided for in this Note,
        all in accordance with the terms hereof.
  **7.2**  Notices .
  (a)    
        Defaults.  The Company will, promptly upon becoming aware
        thereof, notify OccuLogix in writing of any Event of Default, together with
        a
        reasonably detailed description thereof, and the actions the Company proposes
        to
        take with respect thereto;
  (b)    
        Notice of Litigation and Judgments.  The Company will give
        notice to OccuLogix in writing within fifteen (15) business days of becoming
        aware of any litigation or proceedings threatened in writing or any pending
        litigation and proceedings affecting the Company or to which the Company
        is or
        becomes a party involving an uninsured claim against the Company that could,
        in
        each case, reasonably be expected to have a Material Adverse Effect and stating
        the nature and status of such litigation or proceedings; and the Company
        will
        give notice to OccuLogix, in writing, in form and detail reasonably satisfactory
        to OccuLogix, within ten (10) business days of any judgment not covered by
        insurance, final or otherwise, against the Company;
  **7.3**  Legal
        Existence and Good Standing . The
        Company will do or cause to be done all things necessary to preserve and
        keep in
        full force and effect its legal existence and good standing in the State
        of
        Delaware and its good standing and qualification to transact or do business
        in
        each jurisdiction in which the failure to so qualify or be in good standing
        would have a Material Adverse Effect;
  **7.4**  Taxes . The
        Company will duly pay and discharge, or cause to be paid and discharged,
        before
        the same shall become overdue, all taxes, as well as all claims for labor,
        materials, or supplies that if unpaid might by law become a lien or charge
        upon
        any of its property or assets;
  **7.5**  Inspection
        of Properties and Books, etc . The
        Company shall permit OccuLogix upon five (5) business days’ written notice to
        the Company and through its designated representatives, to visit and inspect,
        during regular business hours on a business day, any of the properties of
        the
        Company, to examine the books of account of the Company (and to make copies
        thereof and extracts therefrom), and to discuss the affairs, finances and
        accounts of the Company with, and to be advised as to the same by, its officers,
        all at such reasonable times and intervals as OccuLogix may reasonably request;
        and
  **7.6**  Covenant
        of the Company to Reserve Stock .
        At all
        times prior to the earlier of (a) the conversion of this Note into Conversion
        Shares in accordance with the terms hereof, or (b) the Maturity Date, the
        Company shall reserve, out of its authorized and unissued capital stock,
        an
        adequate number of Conversion Shares such that the Conversion Shares and
        shares
        of Common Stock are immediately issuable upon conversion of this Note. If
        at any
        time the number of authorized but unissued shares of capital stock shall
        not be
        sufficient to enable the conversion of this Note into Conversion Shares,
        the
        Company will take such corporate action as may be necessary to increase its
        authorized but unissued shares of capital stock to such number of shares
        of
        capital stock as shall be sufficient for such purpose.
  **7.7**     
        Use of Proceeds. The Company shall use the Principal Amount,
first, to pay all outstanding obligations under the BSX Note and,
        second, for general corporate purposes.
  **7.8**  Exemption
        from Rights of Participation .
        The
        Company shall (a) obtain continuing and effective written waivers, in a form
        reasonably satisfactory to OccuLogix, or (b) cause to be amended, as soon
        as
        practicable and, in any event, by no later than the end of the Due Diligence
        Period, Section 7.5 of the Amended and Restated Stockholders Agreement, so
        as to
        ensure in either case that the rights of participation of each of Boston
        Scientific Corporation and the Trustees of Boston University, established
        by
        Section 7 of the Amended and Restated Stockholders Agreement, shall have
        no
        application to any Conversion Shares to be issued to OccuLogix in the event
        of
        the conversion of this Note pursuant to Section 3.2 or any subsequent issuances
        of shares of the capital stock of the Company as a result of any anti-dilution
        rights of OccuLogix (as set forth in Section 3.4 below).
  **8.**            
        Negative Covenants. Without limiting the foregoing, the Company covenants
        and agrees that it shall not, so long as this Note is outstanding, directly
        or
        indirectly do or cause, or propose to do or cause, any of the following without
        the prior written consent of OccuLogix:
  **8.1**  Charter
        Documents .
        Cause
        or permit any amendments to its certificate of incorporation or by-laws or
        similar organizational documents, each as in effect on the date hereof, to
        the
        extent it could reasonably be expected to cause a
        material impairment of any rights of OccuLogix under this Note;
  **8.2**  Dividends;
        Changes in Capital Stock .
        Except
        as otherwise specifically contemplated in this Note, (a) declare or pay any
        cash
        dividends or dividends of property on, or make any other distributions (in
        cash
        or property) in respect of, any of its capital stock, or (b) repurchase or
        otherwise acquire, directly or indirectly, any shares of its capital stock
        (other than pursuant to repurchase rights of the Company that permit the
        Company
        to repurchase securities from the holders thereof at the original purchase
        price
        therefor in connection with the termination of services of such holder as
        an
        employee of or consultant to the Company);
  **8.3**  Dispositions .
        Sell,
        lease, license or otherwise dispose of or encumber any of its properties
        or
        assets which are material, individually or when aggregating all such
        dispositions taking place in any 12-consecutive-month period, taken as a
        whole,
        to the conduct of the Company’s business, or that could otherwise be reasonably
        expected to have a Material Adverse Effect, except as part of a Sale of the
        Company;
  **8.4**  Related
        Party Transactions .
        Enter
        into or be a party to any transaction with any director, officer, employee,
        significant stockholder or family member of or consultant to any such person,
        corporation or other entity of which any such person beneficially owns 10%
        or
        more of the equity interests or has 10% or more of the voting power, or
        subsidiary or affiliate of the Company (a “ Related-Party
        Transaction ”)
        except
        as previously approved by (i) a majority of the independent members of the
        Company’s Board of Directors or (ii) the holders of a majority of the
        Independent Shares. Any Related-Party Transaction shall be fair and reasonable
        to the Company and on terms no less favorable to the Company than those that
        could be obtained from unaffiliated third parties. For purposes of this Section
        8.4, “ Independent
        Shares ”
shall
        mean, with respect to any transaction, the shares of outstanding capital
        stock
        of the Company held by stockholders who are not directly interested in such
        transaction;
  **8.5**  Breach
        or Violate Note .
        Take
        any action that could reasonably be expected to materially violate or breach,
        or
        result in a material violation or breach, of the Company’s obligations under
        this Note;
  **8.6**  No
        Impairment .
        Take
        any action that could reasonably be expected to deny OccuLogix the anticipated
        benefits of the conversion rights provided in this Note in any material respect,
        or, if this Note is not so converted, the payment of the Principal Amount
        or
        unpaid accrued interest pursuant to the terms of this Note; or
  **8.7**  General .
        Authorize, commit to, agree to take, or permit to occur any of the foregoing
        actions.
  **9.**             Independent
        Obligations .
        The
        Company agrees and acknowledges that each covenant contained in Sections
        7 and 8
        constitutes an independent obligation of the Company, not qualified by any
        other
        clause, and shall be deemed to be cumulative.
  **10.**          
        No Security Interest. This Note is unsecured and the Company does not
        pledge any assets or other collateral as security for the payment of the
        Principal Amount and interest described in this Note.
  **11.**          
        Reasonable Estimate of Damages. After negotiation, the Company and
        OccuLogix have mutually agreed that, considering all of the circumstances
        existing on the date hereof, the right of OccuLogix to convert this Note
        pursuant to Section 3.2, and the attendant consequences of doing so, represent
        fair and reasonable compensation for damages that OccuLogix would suffer
        as a
        result of the existence of the conditions giving rise to such right. The
        granting of such right is not intended as a forfeiture or penalty but, rather,
        is intended to constitute liquidated damages to OccuLogix. The Company hereby
        specifically confirms the accuracy of the foregoing and its agreement therewith.
        Nothing contained in this Section 11 shall be deemed or construed as a
        limitation on any other rights or remedies that OccuLogix may have hereunder,
        at
        law or in equity, or otherwise.
  **12.**        
         Waiver of Presentment, Etc. The Company hereby, to the fullest
        extent permitted by applicable law, waives presentment, demand, notice, protest,
        and all other demands and notices in connection with delivery, acceptance,
        performance, default, acceleration or enforcement of or under this
        Note.
  **13.**      
           Amendment; Waivers. Neither this Note nor any term
        hereof may be waived, amended, discharged, modified, changed, or terminated
        orally, nor shall any waiver of any provision hereof be effective except
        by an
        instrument in writing signed by the party granting the waiver. The failure
        of
        the holder hereof to exercise any of its rights, remedies, powers, or privileges
        hereunder in any instance will not constitute a waiver thereof, or of any
        other
        right or remedy, and no single or partial exercise of any right or remedy
        shall
        preclude any other or further exercise thereof or of any other right or
        remedy.
  **14.**         
        Payment of Collection Costs. The Company will pay on demand all costs of
        collection, including all court costs and reasonable attorneys’ fees, paid or
        incurred by OccuLogix in enforcing this Note after an Event of
        Default.
  **15.**         
        GOVERNING LAW. THIS NOTE WILL BE GOVERNED BY AND INTERPRETED AND
        CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS OF THE COMMONWEALTH OF
        MASSACHUSETTS (WITHOUT REFERENCE TO PRINCIPLES OF CHOICE OF LAW).
  **16.**          
        Notices. All notices and other communications required or permitted
        hereunder shall be in writing and shall be deemed to have been duly given
        when
        delivered in person or upon confirmation of receipt when transmitted by
        facsimile transmission (but only if followed by national overnight courier
        or
        hand for deliver on the next business day) or on receipt after dispatch by
        registered or certified mail, post prepaid, addressed, or on the next business
        day if transmitted by national overnight courier, in each case as
        follows:
  If
        to the
        Company:
  Solx,
        Inc.
 8
        Saint
        Mary’s Street, Suite 629
 Boston,
        MA 02215
 Attention:
        President
 Telephone:
        617-353-1277
 Facsimile:
        617-358-1933
 
 with
        a
        copy to:
 
 Rackemann,
        Sawyer & Brewster,
 Professional
        Corporation
 One
        Financial Center
 Boston,
        MA 02111
 Attention:
        Jamey A. Wachta, Esq.
 Telephone:
        617-951-1141
 Facsimile:
        617-542-7437
 
 If
        to
        OccuLogix, Inc.:
 
 OccuLogix,
        Inc.
 2600
        Skymark Avenue
 Building
        9, Suite 201
 Mississauga,
        ON Canada L4W5B2
 Attention:  Chief
        Executive Officer
 Facsimile:  905-602-7623
 
 With
        a
        copy to:
 
 Torys
        LLP
 Suite
        3000, 79 Wellington Street West
 Toronto-Dominion
        Centre
 Toronto,
        ON Canada M5K 1N2
 Attention:
        David A. Chaikof
 Facsimile:
        416-865-7380
 
 
 [ *The
        remainder of this page is intentionally left blank.* ]
 
  BUSDOCS/1518918.1
 
 - -
   
 **In
        Witness Whereof** ,
        the
        Company has executed and delivered this Convertible Unsecured Promissory
        Note as
        an instrument under seal as of the date first above written.
 
 **SOLX,
        INC.**
 
 
 By:
        _________________________________
 Name:
        Doug P. Adams
 Title:
        President
 
 **Acknowledged
        and Agreed:**
 
 **OCCULOGIX,
        INC.**
 
 
 By:
        _________________________________
 Name:
        Elias Vamvakas
 Title:
        Chairman and Chief Executive Officer
 
 
 
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