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                                                                   EXHIBIT 10.1

                             FIFTH AMENDMENT TO LEASE

         This Fifth Amendment to Lease (the "Amendment") is made as of this
30th day of April, 1999, by and between Robert F. Tambone, as Trustee of MAT
Realty Trust, u/d/t dated June 4, 1986 and recorded with the Worcester County
Registry of Deeds in Book 9569, Page 286 (the "Landlord") and VISTA Medical
Technologies, Inc., a Delaware corporation, successor in interest to OKTAS, a
Massachusetts general partnership of which OKTAS, Inc., a Massachusetts
corporation and VISTA Medical Technologies, Inc., a California corporation
were the sole general partners (the "Tenant").

         Reference is hereby made to a certain lease (as amended, the
"Lease") dated as of April 14, 1994 by and between Landlord and Tenant; a
certain First Amendment to Lease dated as of March__, 1996 (the "First
Amendment"); a certain Second Amendment to Lease dated as of October 28, 1996
(the "Second Amendment"); a Third Amendment to Lease dated as of September 1,
1997 (the "Third Amendment"); and a Fourth Amendment to Lease dated as of
October 30, 1997; all relating to certain space in the building located at
134 Flanders Road, Westborough, Massachusetts. The Guaranty of Kaiser
Aerospace and Electronics Corporation, a Nevada corporation, remains with
respect to the obligations arising from the 8,733 square feet originally
leased under the Lease (the "Original Premises"), and the obligations of
Tenant under the First Amendment are secured by a security deposit in lieu of
a guaranty. Capitalized terms used herein and not otherwise defined shall
have the meanings set forth in the Lease.

         WHEREAS, Landlord and Tenant desire to extend the term of the Lease
with respect to certain portions of the Premises leased under the Lease, and
in consideration thereof, to increase the rent and otherwise to amend the
Lease in the manner hereinafter provided;

         NOW, THEREFORE, in consideration of the agreements set forth herein
and for other good and valuable consideration, the receipt and sufficiency of
which is hereby acknowledged, Landlord and Tenant hereby amend the Lease as
of May 1, 1999 (the "Effective Date") as follows:

         1. The modifications to the Lease effected hereby are summarized in
the Lease Summary Table attached hereto as Exhibit B. Landlord and Tenant
hereby agree that the information expressed in such Table is true and correct
in all respects. In the event of any inconsistency between the information
described on the attached Lease Summary Table and the amendments described
herein, the information in the attached Table shall govern.

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         2. In addition to the Base Rent described in Section 1.1 of the
Lease, and in addition to the Base Rent described in the First Amendment,
Second Amendment, Third Amendment, and Fourth Amendment, the following is
inserted therewith and added thereto:

         "Original  Premises and First Amendment  Additional  Premises Base
Rent": The sums set forth below, as the same may be adjusted and/or abated
pursuant to this Lease:

         (a)      For the period from and including May 1, 1999 through October
                  31, 2000, One Hundred Eighty Thousand Four Hundred Forty One
                  Dollars ($180,441.00) annually ($15,036.75 monthly) ($13.50
                  per square foot of Premises Rentable Area).

         (b)      For the period from and including November 1, 2000 through
                  October 31, 2001, One Hundred Ninety Three Thousand Eight
                  Hundred Seven and 50/100ths Dollars ($193,807) annually
                  ($16,150.58 monthly) ($14.50 per square foot of Premises
                  Rentable Area).

         "Third Amendment Additional Premises Base Rent" for the period from and
         including September 1, 2001 through October 31, 2001 is hereby modified
         from the $12 per rentable square foot of Premises Rentable Area
         specified in the Third Amendment to the following:

         (a)      Fifty Seven Thousand Nine Hundred Two Dollars ($57,902)
                  annually ($4,825.17 monthly) ($13.00 per square foot of the
                  Premises Rentable Area).

         "Fourth Amendment Additional Premises Base Rent" for the period from
and including May 1, 1999 through October 31, 2002, as follows:

         (a)      For the period from and including May 1, 1999 through October
                  31, 2000, One Hundred Thirty Six Thousand Six Hundred Six and
                  50/100ths Dollars ($136,606.50) annually ($11,383.88 monthly)
                  ($13.50 per square foot of the Premises Rentable Area).

         (b)      For the period from and including November 1, 2000 through
                  October 31, 2001, One Hundred Fifty One Thousand Seven Hundred
                  Eighty Five Dollars ($146,725.50) annually ($12,227.13
                  monthly) ($14.50 per square foot of the Premises Rentable
                  Area).



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         (c)      For the period from and including November 1, 2001 through
                  October 31, 2002, One Hundred Fifty One Thousand Seven Hundred
                  Eighty Five ($151,785) annually ($12,648.75 monthly) ($15.00
                  per square foot of Premises Rentable Area).

                  The Base Rent changes effected by the foregoing shall
                  commence to be due and payable on the Effective Date."

         3. The Term for the Original Premises (8,733 rentable square feet)
and the First Amendment Additional Premises (4,663 rentable square feet)
shall be extended from the Effective Date through October 31, 2001. The Term
for the Second Amendment Additional Premises, the Third Amendment Additional
Premises, and the Fourth Amendment Additional Premises shall be unchanged by
this Fifth Amendment, i.e., the Term Expiration Date for the Second Amendment
Additional Premises and for the Third Amendment Additional Premises shall
continue to be October 31, 2001 and the Term Expiration Date for the Fourth
Amendment Additional Premises shall continue to be October 31, 2002.

         4. Except as otherwise expressly stated herein, the Additional
Premises shall be delivered to Tenant by Landlord in its "AS IS" condition on
the Effective Date and thereupon shall become part of the Premises. Landlord
shall not be obligated to install any tenant improvements. Any work done by
Tenant in the Additional Premises shall be done in full compliance with all
applicable laws and regulations, with Section 5.2 of the Lease, and with all
other applicable provisions of the Lease.

         5. Landlord and Tenant agree that Tenant shall be obligated to pay,
in the manner specified in Section 8.2 of the Lease, a management fee of
three (3%) percent of Base Rent for the entire Term relative to the Premises,
the Additional Premises, the Second Amendment Additional Premises, the Third
Amendment Additional Premises and the Fourth Amendment Additional Premises.

         Except as expressly set forth herein, the Lease shall remain
unmodified and in full force and effect.

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         IN WITNESS WHEREOF, Landlord and Tenant have caused this Amendment to
be duly executed, under seal, by persons hereunto duly authorized, in multiple
copies, each to be considered an original hereof, as of the date first set forth
above.

                                            LANDLORD:


                                             /s/ ROBERT F. TAMBONE
                                             ---------------------
                                             Robert F. Tambone, Trustee as
                                             aforesaid and not individually



                                             TENANT:

                                             VISTA MEDICAL TECHNOLOGIES, INC., a
                                             Delaware corporation


                                             By: /s/ JOHN LYON
                                                --------------------
                                             Name: JOHN LYON
                                                --------------------
                                             Title: PRESIDENT
                                                --------------------