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                                                                     Exhibit 4.5

                             AMENDMENT NO. 1 TO THE
                                RIGHTS AGREEMENT
                            OF SUMMIT AUTONOMOUS INC.
                         (F/K/A SUMMIT TECHNOLOGY, INC.)



         This Amendment No. 1, dated as of May 26, 2000, amends the Rights
Agreement dated as of March 28, 2000 (the "RIGHTS AGREEMENT"), between Summit
Autonomous Inc., f/k/a Summit Technology Inc., a Massachusetts corporation (the
"COMPANY"), and Fleet National Bank (f/k/a BankBoston, N.A.), as Rights Agent
(the "RIGHTS AGENT"). Terms defined in the Rights Agreement and not otherwise
defined herein are used herein as so defined.

                              W I T N E S S E T H:

         WHEREAS, on March 28, 2000, the Board of Directors of the Company
authorized the issuance of Rights to purchase, on the terms and subject to the
provisions of the Rights Agreement, shares of the Company's Preferred Stock;

         WHEREAS, on March 28, 2000, the Board of Directors of the Company
authorized and declared a dividend distribution of one Right for every share of
Common Stock of the Company outstanding on the Dividend Record Date and
authorized the issuance of one Right (subject to certain adjustments) for each
share of Common Stock of the Company issued between the Dividend Record Date and
the Distribution Date;

         WHEREAS, the Distribution Date has not occurred; and

         WHEREAS, pursuant to Section 27 of the Rights Agreement, the Board has
approved an amendment of certain provisions of the Rights Agreement as set forth
below;

         NOW, THEREFORE, the Rights Agreement is hereby amended as follows:

         1. Section 1(a) is amended by deleting the phrase "or (v)" after clause
(iv) and adding the following language:

            "(v) an Exempt Person, or (vi)"

         2. A new definition is added after Section 1(w) and before Section 1(x)
as follows:

            "(w') "Exempt Person" shall mean Alcon Acquisition Corp., a
            Massachusetts corporation ("SUB"), and its Affiliates solely to the
            extent any such Person becomes the Beneficial Owner of 15% or more
            of the shares of Common Stock then outstanding by reason of the
            execution of, or the consummation of the

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            transactions contemplated by, the Agreement and Plan of Merger,
            dated as of May 26, 2000 (the "MERGER AGREEMENT"), by and among
            Alcon Holdings Inc., a Delaware corporation, Sub and the Company;
            PROVIDED, that this Section 1(w') shall automatically be of no
            further force and effect at and after such time as the Merger
            Agreement is terminated pursuant to Section 8.01 thereof.

         3. Section 1(y) is amended by deleting the phrase "or (iv)" after
clause (iii) and adding the following language:

            ", (iv) an Exempt Person, or (v)"

         4. The first sentence of Section 7(a) is amended and restated in its
entirety as follows:

            "Except as otherwise provided herein, the registered holder of any
            Rights Certificate may exercise Rights evidenced thereby in whole or
            in part at any time from and after the Distribution Date and at or
            prior to the earlier of (i) the Close of Business on March 28, 2010
            or (ii) the effective time of the merger contemplated by the Merger
            Agreement (PROVIDED, that this clause (ii) shall automatically be of
            no further force and effect at and after such time as the Merger
            Agreement is terminated pursuant to Section 8.01 thereof) (the
            earlier of such time being, the "Expiration Date") or the earlier
            redemption of the Rights."

         5. Section 24(a) is amended by deleting the phrase "or (iv)" after
clause (iii) in the last sentence and adding the following language:

            "(iv) an Exempt Person, or (v)"

         6. Except as hereby modified and amended, the Rights Agreement shall
remain in full force and effect and unchanged.




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         IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1
to the Rights Agreement to be duly executed as of the day and year first above
written.




                                            SUMMIT AUTONOMOUS INC.


                                            By: /s/ ROBERT J. KELLY
                                               ------------------------------
                                            Title: Chief Financial Officer


Attest:

By: /s/ P. Bernard Haffey
   ----------------------------




                                            FLEET NATIONAL BANK


                                            By: /s/ Tyler Haynes
                                               ------------------------------
                                            Title: Managing Director


Attest:

By: /s/ James Walsh
   ----------------------------