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                                                                   Exhibit 10.25

                      THIRD AMENDMENT TO LEASE AGREEMENT

THIS THIRD AMENDMENT TO LEASE AGREEMENT (the "Third Amendment") is made and
entered into this 3rd day of September, 1999, by and between FIRST INDUSTRIAL,
L.P., a Delaware Limited Partnership ("Landlord"), and OPTICAL SENSORS
INCORPORATED, a Delaware corporation ("Tenant").

                                  WITNESSETH:

WHEREAS, Landlord and Tenant have heretofore entered into a certain Standard
Commercial Lease dated October 7, 1991 (the "Original Lease") pursuant to which
Landlord leased to Tenant and Tenant leased from Landlord certain premises
commonly known as 7615 Golden Triangle Drive, Suite A, Eden Prairie, Minnesota
(the "Premises"); and

WHEREAS, Landlord and Tenant entered into a certain First Amendment to Lease
Agreement dated April 26, 1996 (the "First Amendment"; the original Lease and
the First Amendment are hereinafter collectively referred to as the "Lease");
and

WHEREAS, Landlord and Tenant entered into a certain Second Amendment to Lease
Agreement dated April 14, 1997 (the "Second Amendment"; the Original Lease and
Second Amendment are hereinafter collectively referred to as the "Lease");

NOW, THEREFORE, for good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, the parties hereto hereby agree as follows:

1.  Recitals.  The foregoing recitals are hereby incorporated as if fully
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    rewritten and restated in the body of this Third Amendment. All initially
    capitalized terms used but not defined herein shall have the meanings
    ascribed to such terms in the Lease.

2.  Term.  The term of the Lease shall be extended through May 31, 2000.
    ----

3.  Premises.  The premises shall total 18,339 square feet; (7,906 square feet
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    office, 8,205 square feet lab, 2,228 square feet warehouse) located at 7615
    Golden Triangle Drive, Suite A, as attached on Exhibit A.

4.  Tenant's Proportionate Share.  Tenant's Proportionate Share of Operating
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    Expenses shall be 14.56%.

5.  Base Rent.  Effective December 1, 1999, the monthly Base Rent for the
    ---------
    Premises shall be $11,888.00.

6.  Full Force and Effect.  Except as otherwise expressly set forth in this
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    Third Amendment, all terms, provisions and covenants set forth in the Lease
    shall remain in full force and effect and are hereby ratified and confirmed
    as of the date hereof.
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7.  Conflicts.  In the event that any of the terms, covenants and conditions of
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    this Third Amendment conflict with any of the terms, covenants and
    conditions of the Lease, the terms, covenants and conditions of this Third
    Amendment shall control.

IN WITNESS WHEREOF, the parties hereto have executed this Third Amendment as of
the date and year first above written.


LANDLORD: FIRST INDUSTRIAL, L.P.,       TENANT: OPTICAL SENSORS INCORPORATED, a
a Delaware Limited Partnership          Delaware corporation

By: First Industrial Realty Trust,
    Inc., a Maryland corporation, its
    general partner

By: /s/ Signature illegible             By: /s/ Paulita M. LaPlante
    -----------------------------           -----------------------------

Its: Regional Director                  Its: President & CEO
     ----------------------------            ----------------------------

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