<PAGE>
                                                                   EXHIBIT 10.28
 
                                                                  EXECUTION COPY
 
       AGREEMENT dated as of November 20, 1995, among VISX, INCORPORATED,
       a Delaware  corporation  ("VISX"),  ALCON  LABORATORIES,  INC.,  a
       Delaware  corporation ("ALI"), and  ALCON PHARMACEUTICALS, LTD., a
       corporation organized and existing  under the laws of  Switzerland
       ("APL"  and, together with ALI, "Alcon")  (VISX, ALI and APL being
       referred to herein as the "Parties").
 
    WHEREAS the  Parties  are parties  to  the Amended  and  Restated  Marketing
Agreement dated as of April 21, 1987 (the "First Agreement"), the Second Amended
and  Restated Marketing  Agreement dated  as of  December 22,  1989 (the "Second
Agreement") and certain letter agreements dated as of December 11, 1989 and  May
22, 1990 (the "Letter Agreements" and, together with the First Agreement and the
Second Agreement, the "Marketing Agreements");
 
    WHEREAS  the Parties,  CAP Advisers Limited,  Charles R.  Munnerlyn, Alan R.
McMillen, William L. Bennett, Daniel J. Kunst, Karen Brenner, Robert B. Samuels,
Robert R.  Montgomery,  Timothy R.G.  Sear,  Edgar H.  Schollmaier,  Anthony  M.
Pilaro, Richard S. Braddock and Osterfak, Ltd. simultaneously with the execution
of  this  Agreement, are  entering into  a Settlement  Agreement dated  the date
hereof (the  "Settlement  Agreement"),  which provides  for  the  settlement  of
certain  litigation in Case No.  744052 in the Superior  Court of California and
relating to claims between the parties  to the Settlement Agreement and  certain
other parties; and
 
    WHEREAS the Parties desire to terminate the Marketing Agreements and restate
the  terms  of their  relationship presently  and  subsequent to  the "Effective
Date", as defined in the Settlement Agreement.
 
    NOW, THEREFORE, the parties agree as follows:
 
                                   ARTICLE I
                                  DEFINITIONS
 
    SECTION 1.01.  SPECIFIC  DEFINITIONS.  For purposes  of this Agreement,  the
following terms shall have the following meanings:
 
        "Affiliate"  of  any Party  shall mean  any other  Person which  owns or
    controls, is owned  or is  controlled by, or  is under  common ownership  or
    control  with,  such  Party.  As  used  herein,  "control"  shall  mean  the
    possession, direct  or  indirect,  of  the power  to  direct  or  cause  the
    direction  of  management  or  policies of  a  Person,  whether  through the
    ownership of voting securities, by contract or otherwise.
 
        "Effective Date"  shall mean  the Effective  Date as  set forth  in  the
    Settlement Agreement.
 
        "FDA"  shall mean the United States  Food and Drug Administration or its
    successor.
 
        "Hyperopia Module" shall  mean that hardware  and software necessary  to
    enable a VISX System to perform hyperopia.
 
        "Model B Units" shall mean the VISX Excimer Laser System, Model B.
 
        "Model C Units" shall mean the VISX Excimer Laser System, Model C.
 
        "Operating  Committee"  shall mean  the Operating  Committee established
    under the terms of the Second Agreement.
 
        "Person" shall mean  any natural person,  entity, corporation,  business
    trust,   joint   venture,  association,   company,  partnership,   trust  or
    government, or any agency or political subdivision thereof.

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        "PRK" shall mean photorefractive keratectomy.
 
        "Procedure Royalty"  shall  mean  an  amount, whether  in  the  form  of
    license,  use fees or otherwise, charged to  each purchaser and/or user of a
    VISX System for the use of such VISX System.
 
        "Representatives" of  any Person  shall  mean such  Person's  directors,
    officers, employees, agents and representatives, distributors, sales agents,
    attorneys, accountants, financial advisers and other consultants.
 
        "Transition Period" shall mean the period from and including October 27,
    1995  to and including the Effective  Date, unless this Agreement is earlier
    terminated in accordance with its terms.
 
        "Unit" shall mean an individual VISX System as manufactured by VISX.
 
        "United States"  shall  mean the  50  states  of the  United  States  of
    America, the District of Columbia, Puerto Rico and the other territories and
    possessions of the United States of America.
 
        "VisionKey  Card"  shall mean  the cards  which contain  the proprietary
    software necessary to perform procedures with a VISX System.
 
        "VISX System"  shall mean  any  laser system  manufactured by  VISX  for
    correcting  the refractive optical property  of an eye through photoablative
    sculptured change  in the  cornea, or  for the  treatment of  eye  disorders
    involving corneal opacities, including, without limitation, the treatment of
    superficial   corneal  scars,  epithelial   irregularities  and  fungal  and
    bacterial ulcers.
 
                                   ARTICLE II
 
    SECTION 2.01.  SUSPENSION  OF MARKETING AGREEMENTS.   During the  Transition
Period,  the Marketing Agreements shall be suspended  and shall not be deemed to
define the rights  or obligations  of the Parties  with respect  to the  subject
matter  thereof, and the only rights and obligations of the Parties with respect
to the subject matter of the Marketing Agreements shall be as set forth in  this
Agreement.  If this Agreement  shall terminate in  accordance with Section 5.01,
then the Marketing Agreements shall continue  in full force and effect from  the
date  of such termination. Any action taken  pursuant to this Agreement, and any
failure to take any action not required by this Agreement, during the Transition
Period shall be deemed to be and have been consistent with and not in  violation
or  breach  of the  Marketing Agreements  even  if this  Agreement should  be so
terminated and the  Marketing Agreements so  continued; provided, however,  that
any  arrangement or  transaction entered into  by a Party  during the Transition
Period pursuant  to  Section 2.07(a)  shall  be  capable of  being  modified  or
terminated  by such Party without  the consent of any  third party to the extent
necessary  to  permit  such  Party  to  resume  compliance  with  the  Marketing
Agreements if this Agreement is terminated.
 
    SECTION  2.02.  EXISTING UNIT  ORDERS.  (a) Alcon  will withdraw its request
that VISX repurchase (***) Units  shipped to  it on or before (***),  and  shall
pay to  VISX (***) of any  currently outstanding balance of  the purchase  price
for the last ten units shipped in (***), by each of (***), (***),  (***), (***),
(***) and (***).  VISX shall install, at VISX's sole  cost, in each Model C Unit
shipped to Alcon on or before (***), (i) (***)  and  (ii)  (***). These  payment
and upgrade obligations shall  survive  the Effective  Date  and the termination
of this Agreement.

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    (b) During the Transition Period and  after the Effective Date, Alcon  shall
not  have any obligation to  purchase any Units in  addition to those shipped by
VISX to Alcon on  or before (***), notwithstanding any orders for Units that may
have been placed  by Alcon or which any  of the Parties may have forecasted  for
purchase by Alcon after (***).
 
    SECTION 2.03.   BUDGETS.   The supplemental  budget for  the quarter  ending
December  31, 1995, previously submitted to the Operating Committee in September
1995 (a  copy of  which is  attached  as Exhibit  I hereto)  (the  "Supplemental
Budget") is hereby approved, except that no amounts shall be deemed to have been
budgeted for Alcon to perform service of Units or physician training as provided
therein.  In the  event that  the FDA grants  approval for  PRK use  of the VISX
Systems on or prior to  December 31, 1995, VISX and  Alcon agree to negotiate  a
modification  of such supplemental budget to take account of such approval. VISX
shall, no later than 30 days following receipt of Alcon's invoice, make  payment
to  Alcon for  all marketing  costs and expenses  relating to  the quarter ended
September 30, 1995  included in  budgets previously submitted  to the  Operating
Committee  but not yet paid. Alcon shall perform all tasks that are specifically
provided by the Supplemental  Budget, except that it  shall not be obligated  to
perform service of Units or physician training. VISX shall pay, no later than 30
days  following receipt  of Alcon's invoice,  all documented  costs and expenses
incurred by Alcon pursuant to the original and supplemental budgets submitted to
the Operating Committee for the quarter ending December 31, 1995 as such budgets
are modified as provided above.
 
    SECTION 2.04.   INTERNATIONAL USERS MEETING.   Alcon and  VISX hereby  agree
that  the international  users meeting  previously scheduled  for February 8-10,
1996 shall be cancelled.
 
    SECTION 2.05.  CERTAIN CLAIMS.  Each Party shall fully cooperate and provide
to the other Party, upon request, all relevant documents and other materials and
information relating to  any claims  against insurers, carriers  or other  third
parties for damage caused to any Units previously sold to Alcon during shipping,
transporting  or handling  of such  Units. This  Section 2.05  shall survive the
Effective Date and the termination of this Agreement.
 
    SECTION 2.06.  HIRING  OF EMPLOYEES.  During  the Transition Period and  for
the  period until 5  years after the  Effective Date, VISX  and Alcon agree that
neither VISX nor Alcon shall solicit for employment any person then employed  by
the  other Party; and neither VISX nor  Alcon shall employ any individual who is
or was employed by the other Party if such employment is known by such Party  to
be  in violation  of any  employment or  non-competition agreement  to which the
other Party is a signatory. VISX and Alcon agree to make reasonable inquiries as
to the existence of any such agreement.
 
    SECTION 2.07.  PREPARATION FOR TERMINATION OF MARKETING AGREEMENTS.  (a)  In
anticipation  of the termination of the  Marketing Agreements but subject to the
proviso to Section 2.01,  during the Transition Period  Alcon shall be free  and
clear  to make any and all arrangements, and to effect any transactions in order
to arrange, for  the sale  (or the  facilitation or  financing of  the sale)  of
systems  competitive with  VISX Systems  by Alcon  or any  of its  Affiliates or
Representatives or for  the purchase (or  the facilitation or  financing of  the
purchase)   of   such  competitive   systems   by  Alcon   or   its  Affiliates,
Representatives or customers subsequent to  the Effective Date. In  anticipation
of  the termination of  the Marketing Agreements  but subject to  the proviso to
Section 2.01, during the Transition Period VISX shall be free and clear to  make
any  arrangements, and to effect  any transactions in order  to arrange, for the
sale of  VISX  Systems  by VISX  or  through  third parties  subsequent  to  the
Effective Date.
 
    (b)  Alcon agrees to provide to VISX, on  or prior to November 27, 1995, all
material information relating to the quotation of prices and leads for sales  of
VISX  Systems in Alcon's possession, with respect  to VISX Systems to be sold in
the United States and, upon the sale or other disposition by Alcon of all  Units
currently  held by Alcon in its inventory (such date being the "Transfer Date"),
to provide to VISX all material information relating to the quotation of  prices
and  leads then  in Alcon's  possession with  respect to  sales of  VISX Systems
outside the United States.

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    SECTION 2.08.   VISIONKEY CARDS FOR  PREVIOUSLY SHIPPED UNITS.   During  the
Transition  Period, Alcon shall  have the right to  purchase from VISX VisionKey
Cards for use on the  Units sold and shipped to  Alcon on or prior to  (***) and
set forth in Exhibit II  hereto at the prices  currently being  charged to Alcon
by VISX. On and after the Effective Date, Alcon shall have the right to purchase
VisionKey  Cards for use on such Units, as well as any Unit which Alcon provides
to its customers in exchange for a defective Unit (including without  limitation
any  Unit  provided  in  exchange  for a  Unit  which  is  not able  to  perform
hyperopia),  at  the  following  initial  prices  for  each VisionKey  Card: (a)
(***) for Units in use in (***) or (***) or sold from Alcon's existing inventory
for use in  (***) or  (***); (b) (***) for  Units in  use by Alcon end customers
(***); and (c) (***) for   all other  Units  currently  in  use (***);  PROVIDED
that  the initial  price  for  each  VisionKey  Card for  use on  (x) (***)  and
(y) (***);   PROVIDED  FURTHER,  HOWEVER,  that  clause (y) of  the  immediately
preceding proviso  shall  not apply to (1) (***) or  (2)  (***) VisionKey  Cards
purchased  by Alcon's end  users  for (***) shall  include (***).  On  or  after
each annual anniversary of  the  Effective  Date, VISX shall have the right to 
increase the  prices for VisionKey Cards sold to Alcon; PROVIDED, HOWEVER, that
(***) such cost increases to be substantiated by VISX by  providing Alcon with 
written proof of such price increases by such manufacturer.
 
    SECTION 2.09.  SALES OF VISX STOCK BY ALCON.  Alcon agrees that it will  not
sell  any of the 224,000 shares of Common Stock of VISX currently owned by Alcon
before January 24, 1996.
 
    SECTION 2.10.   USE  OF INFORMATION  FOR  MARKETING BY  ALCON.   During  the
Transition  Period and after the  Effective Date, Alcon shall  have the right to
use any information obtained from purchasers  and users of VISX Systems sold  by
Alcon for the marketing and sale of any equipment or other products manufactured
by Alcon or any of its Affiliates or purchased by Alcon or any of its Affiliates
from  third  parties for  resale; PROVIDED  that  Alcon shall  not use  any such
information which  Alcon knows  or  has reason  to  believe to  be  confidential
proprietary  information  of VISX  without the  prior  permission of  VISX, such
permission by VISX not to be unreasonably withheld or delayed.
 
    SECTION 2.11.   NOTICE  OF ADVERSE  MEDICAL EVENTS.   Alcon  shall  promptly
notify  VISX  of any  material adverse  medical events  reported to  Alcon which
relate to  VISX Systems  sold by  Alcon.  This Section  2.11 shall  survive  the
Effective  Date. Alcon agrees to use  commercially reasonable efforts to forward
to VISX on  a monthly basis  all copies  of service reports  regarding the  VISX
Systems  serviced by Alcon, coded with the  problem and "work done" codes agreed
to with VISX.
 
                                  ARTICLE III
 
    SECTION 3.01.  EFFECTIVENESS OF ARTICLE III.  Except as provided in the last
sentence of Section 3.04, the provisions  of this Article III shall only  become
effective  upon, and shall be conditioned  upon the occurrence of, the Effective
Date.
 
    SECTION 3.02.  TERMINATION OF MARKETING AGREEMENTS.  (a) Upon the  Effective
Date,  each of  the Marketing Agreements  shall terminate  immediately and shall
have no remaining  effect. Except  as specifically provided  in this  Agreement,
termination  of  the Marketing  Agreements pursuant  hereto shall  terminate all
rights and obligations of the Parties under the Marketing Agreements,  including

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rights and obligations (including without limitation the license granted to VISX
by Alcon pursuant to Section 2.06 of the Second Agreement) that, under the terms
of the Marketing Agreements, would otherwise have survived their termination.
 
    (b)  Alcon  hereby  agrees,  following the  Effective  Date,  to  sell Alcon
pharmaceutical  products  to  VISX  as  priced  to  wholesalers,  for  (***) and
thereafter on a commercially reasonable basis.
 
    SECTION  3.03.  FRENCH AND JAPANESE  REGISTRATIONS.  Alcon or its Affiliates
shall promptly provide to VISX all  pertinent data relating to the  registration
of  the  VISX  Systems  in  France and  Japan  (the  "French  Registrations" and
"Japanese Registrations",  respectively).  Such  data shall  include  data  with
respect  to the  status and  the transferability  of such  registrations and the
out-of-pocket costs  and  expenses  incurred  by  Alcon  or  its  Affiliates  in
connection  with  seeking such  registrations. VISX  shall  have the  option, by
providing written notice to Alcon or Alcon's Appropriate Affiliate no later than
60 days subsequent  to the  Effective Date,  and upon  payment to  Alcon or  its
Affiliates  equal  to all  of Alcon's  or its  Affiliate's documented  costs and
expenses relating thereto,  to acquire  Alcon's or its  Affiliate's rights  with
respect  to  either  or  both  of  the  French  Registrations  and  the Japanese
Registrations.  Alcon  shall  cooperate  fully  with  VISX  in  effecting   such
transfers.
 
    SECTION 3.04.  UNITS SOLD IN CANADA.  In consideration of the other terms of
this Agreement, APL and Alcon Canada shall have from VISX (***)  relating to the
(***); PROVIDED, HOWEVER, that the (***). Prior  to any  sale of any  Unit not a
Licensed Unit, which to Alcon's or any of its Affiliates' knowledge will be  for
use  in Canada,  and prior to  the subsequent  sale of any  such Unit, including
those listed on Exhibit III,  by Alcon or any of  its Affiliates to a party  not
listed  as a user of a  Unit on Exhibit III hereto,  Alcon or such Affiliate, as
applicable, shall (***).
 
    SECTION 3.05.  SERVICE OF UNITS SOLD  BY ALCON.  Alcon shall be  responsible
for  the  servicing of all Units designated in Exhibit II hereto. Through (***),
VISX shall make available to Alcon parts, manuals, training and other
materials for the servicing  of such Units  at the same prices  and on the  same
terms  as are  available from  VISX on  the date  of this  Agreement. Subject to
Section 3.07,  after  (***),  VISX  shall  make  available  to Alcon such parts,
manuals, training and other materials on a commercially reasonable basis.
 
    SECTION  3.06.    (***)
 
    SECTION  3.07.  NONDISCRIMINATION IN  SALES OF VISX SYSTEMS.   Alcon and any
customer of  Alcon shall  have the  right to  purchase VISX  Systems,  including
VisionKey  Cards and any related  parts, manuals or services  from VISX on terms
that do not discriminate against Alcon  or its customers in comparison to  other
distributors and end users of VISX Systems similarly situated.

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    SECTION  3.08.  CANCELLATION OF ALI ADVANCE.   In consideration of the other
terms of this  Agreement,  VISX  shall  not  be  obligated  to  repay the  (***)
advanced  to VISX by ALI  under the Marketing Agreements  and ALI shall not seek
any payment  from  VISX  relating  to  such  advance  in  consideration  of  the
settlement by VISX of any claims it may assert against ALI.
 
    SECTION  3.09.   PURCHASES  OF VISX  VOTING SECURITIES.   During  the period
commencing (***)  and  ending  on  (***), Alcon  shall not purchase or otherwise
acquire any stock or other security issued by VISX that has the general power to
vote in the election of directors of VISX ("Voting Securities").
 
                                   ARTICLE IV
                         REPRESENTATIONS AND WARRANTIES
 
    SECTION 4.01.  VISX.   VISX represents  and warrants to  Alcon that (a)  the
execution  and delivery  by VISX  of this Agreement  and the  performance of the
activities contemplated hereby  are duly authorized  by all necessary  corporate
action  on its part  and do not  contravene its Certificate  of Incorporation or
By-laws or any agreement binding  upon VISX or VISX's  assets; and (b) VISX  and
its Affiliates have no prior commitments or agreements with any third party that
might  interfere with or preclude the full and complete discharge by VISX of its
obligations and undertakings pursuant to this Agreement.
 
    SECTION 4.02.  ALCON.   Alcon represents and warrants  to VISX that (a)  the
execution  and delivery by  Alcon of this  Agreement and the  performance of the
activities contemplated hereby  are duly authorized  by all necessary  corporate
action  on its part  and do not  contravene its Certificate  of Incorporation or
By-laws or any agreement binding upon Alcon or Alcon's assets; and (b) Alcon and
its Affiliates have no prior commitments or agreements with any third party that
might interfere with or preclude the full and complete discharge by Alcon of its
obligations and undertakings pursuant to this Agreement.
 
                                   ARTICLE V
                                 MISCELLANEOUS
 
    SECTION 5.01.   TERMINATION.    Either Party  may  elect to  terminate  this
Agreement if the Effective Date does not occur by February 28, 1996 by providing
written notice to the other Party.
 
    SECTION  5.02.  AMENDMENT.   This Agreement  may not be  changed or modified
except as specifically and mutually agreed upon in writing and signed by all the
Parties.
 
    SECTION 5.03.  NOTICE.  Any notice  required hereunder may be served by  any
Party  on the others by  personal delivery, or by  sending same post-prepaid, by
registered or  by certified  mail, return  receipt requested,  to the  following
addresses:
 
        (a) If to Alcon:
 
            Alcon Laboratories, Inc.
           6201 South Freeway
           Fort Worth, Texas 76134
           Attn: E. H. Schollmaier
 
        (b) If to VISX:
 
            VISX, Incorporated
           3400 Central Expressway
           Santa Clara, California 95051-0703
           Attn: Mark B. Logan
 
    or to such other person or at such other place as any Party shall notify the
    other Parties in writing.

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    SECTION  5.04.  WAIVER.  The Parties covenant and agree that a waiver by any
Party of a breach of any of the terms of this Agreement by any other Party shall
not be deemed a waiver  of any subsequent breach of  the same or other terms  of
this  Agreement. No failure or delay in exercising any right, power or privilege
hereunder shall operate  as a waiver  thereof, nor shall  any single or  partial
exercise  thereof preclude any other or further exercise thereof or the exercise
of any other right, power or privilege hereunder.
 
    SECTION 5.05.  SPECIFIC PERFORMANCE.  The Parties agree that in the event of
a breach of  any provision of  this Agreement the  aggrieved Party would  suffer
irreparable  harm and therefore would be without  an adequate remedy at law. The
Parties therefore agree that in  the event of a  breach or threatened breach  of
any  provision  of this  Agreement,  the aggrieved  Party  shall be  entitled to
institute and prosecute proceedings  in any court  of competent jurisdiction  to
enforce  specific  performance  or  to  enjoin  the  continuing  breach  of such
provision without  the requirement  of  posting a  bond  or other  security.  By
seeking  or obtaining any such relief, the aggrieved Party will not be precluded
from seeking or obtaining any other relief to which it may be entitled.
 
    SECTION 5.06.  LITIGATION.  If  any Party institutes legal proceedings  with
respect to this Agreement or the transactions contemplated hereby, the losing or
defaulting  Party shall pay to the  prevailing Party reasonable attorneys' fees,
costs and expenses  incurred in connection  with the prosecution  or defense  of
such action.
 
    SECTION  5.07.  CAPTIONS.   The captions  and section headings  used in this
Agreement are for convenience only and are not intended to have, nor shall  they
be interpreted as having, any substantive effect whatsoever.
 
    SECTION  5.08.   EXPENSES.    Each of  the  parties hereto  shall  be deemed
responsible for all expenses incurred by it in connection with the execution and
performance of this Agreement except as otherwise provided for herein.
 
    SECTION 5.09.  GOVERNING LAW.  This  Agreement is made and entered into  and
is  to be  performed in accordance  with the laws  of the State  of Delaware and
shall be construed  and enforced in  accordance with  the laws of  the State  of
Delaware, without regard to its principles of conflicts of laws.
 
    SECTION  5.10.   SEVERABILITY.   The invalidity  or unenforceability  of any
provision  of  this  Agreement  shall  not  affect  or  limit  the  validity  or
enforceability of any other provision hereof.
 
    SECTION  5.11.  ENTIRE AGREEMENT; THIRD PARTY BENEFICIARIES.  This Agreement
including the Exhibits referred to  herein (a) constitutes the entire  agreement
and,  subject to Section 2.01, supersedes all prior agreements and undertakings,
both written and  oral, among  the parties with  respect to  the subject  matter
hereof,  including  the  Marketing Agreements  and  the term  sheet  between the
Parties dated October  27, 1995,  and (b)  is not  intended to  confer upon  any
person other than the parties hereto any rights or remedies hereunder.
 
    SECTION  5.12.  COUNTERPARTS.  This Agreement may be executed in one or more
counterparts, each of which will be deemed an original but all of which together
shall constitute a single instrument.


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    IN WITNESS WHEREOF, the Parties have caused this Agreement to be executed by
their fully authorized officers as of the date first above written.
 
                                          VISX, INCORPORATED,
                                            by /s/ Elizabeth Davila
                                               _________________________________
                                               Elizabeth Davila
                                              EXECUTIVE VICE PRESIDENT
                                              AND CHIEF OPERATING OFFICER
 
                                          ALCON LABORATORIES, INC.,
                                            by /s/ C. Allen Baker
                                               _________________________________
                                               C. Allen Baker
                                              EXECUTIVE VICE PRESIDENT,
                                              SURGICAL
 
                                          ALCON PHARMACEUTICALS, LTD.,
                                            by /s/ Guido Koller
                                               _________________________________
                                               Guido Koller
                                               GENERAL MANAGER/AREA CONTROLLER


(***) Confidential Treatment Requested

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