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                                                                   EXHIBIT 10.23


                         CHANGE OF CONTROL AGREEMENT


     This Change of Control Agreement (the "Agreement") is made and entered into
effective as of May 6, 1997, by and between Thomas M. Loarie (the "Employee")
and KeraVision, Inc., a Delaware corporation (the "Company").


                                    RECITALS

     A.  It is expected that another company or other entity may from time to
time consider the possibility of acquiring the Company or that a change in
control may otherwise occur, with or without the approval of the Company's Board
of Directors (the "Board").  The Board recognizes that such consideration can be
a distraction to the Employee, a corporate officer of the Company, and can cause
the Employee to consider alternative employment opportunities.  The Board has
determined that it is in the best interests of the Company and its stockholders
to assure that the Company will have the continued dedication and objectivity of
the Employee, notwithstanding the possibility, threat or occurrence of a Change
of Control (as defined below) of the Company.

     B.  The Board believes that it is in the best interests of the Company and
its stockholders to provide the Employee with an incentive to continue his or
her employment with the Company.

     C.  The Board believes that it is imperative to provide the Employee with
certain benefits upon a Change of Control and, under certain circumstances, upon
termination of the Employee's employment in connection with a Change of Control,
which benefits are intended to provide the Employee with financial security and
provide sufficient income and encouragement to the Employee to remain with the
Company notwithstanding the possibility of a Change of Control.

     D.  To accomplish the foregoing objectives, the Board of Directors has
directed the Company, upon execution of this Agreement by the Employee, to agree
to the terms provided in this Agreement.

     E.  Certain capitalized terms used in the Agreement are defined in Section
4 below.

     In consideration of the mutual covenants contained in this Agreement, and
in consideration of the continuing employment of Employee by the Company, the
parties agree as follows:

          1.  At-Will Employment.  The Company and the Employee acknowledge that
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the Employee's employment is and shall continue to be at-will, as defined under
applicable law.  If the Employee's employment terminates for any reason,
including (without

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limitation) any termination prior to a Change of Control, the Employee shall not
be entitled to any payments or benefits, other than as provided by this
Agreement, or as may otherwise be available in accordance with the terms of
Employee's Employment Agreement with the Company dated January 1, 1997 (the
"Employment Agreement") the Company's established employee plans and written
policies at the time of termination.  The terms of this Agreement shall
terminate upon the earlier of (i) the date on which Employee ceases to be
employed as a corporate officer of the Company, other than as a result of an
involuntary termination by the Company without Cause (ii) the date that all
obligations of the parties hereunder have been satisfied, or (iii) two (2) years
after a Change of Control.  A termination of the terms of this Agreement
pursuant to the preceding sentence shall be effective for all purposes, except
that such termination shall not affect the payment or provision of compensation
or benefits on account of a termination of employment occurring prior to the
termination of the terms of this Agreement.

          2.  Stock Options.  Subject to Sections 5 and 6 below, in the event of
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a Change of Control and regardless of whether the Employee's employment with the
Company is terminated in connection with the Change of Control, each stock
option granted for the Company's securities (the "Options") held by the Employee
shall become fully vested and immediately exercisable on the effective date of
the transaction by the Option and shall be exercisable to the extent so vested
in accordance with the provisions of the Option Agreement and Plan pursuant to
which such option was granted.

          3.  Change of Control.
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              (a) Termination Following A Change of Control.  Subject to
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Section 5 and 6 below, if the Employee's employment with the Company is
terminated at any time within two (2) years after a Change of Control, then
the Employee shall be entitled to receive severance benefits as follows:

                  (i) Voluntary Resignation.  If the Employee voluntarily
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resigns from the Company (other than as an Involuntary Termination (as defined
below) or if the Company terminates the Employee's employment for Cause (as
defined below)), then the Employee shall not be entitled to receive severance
payments. The Employee's benefits will be terminated under the terms of the
Employee Agreement and the Company's then existing benefit plans and policies
in accordance with such plans and policies in effect on the date of
termination or as otherwise determined by the Board of Directors of the
Company.

                  (ii) Involuntary Termination.  If the Employee's employment is
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terminated as a result of an Involuntary Termination other than for Cause, the
Employee shall be entitled to receive the following benefits:  (i) severance
payments during the period from the date of the Employee's termination until the
date 18 months after the effective date of the termination (the "Severance
Period") equal to the salary which the Employee was receiving at the time of
such termination, which payments shall be paid during the Severance Period in
accordance with the Company's standard payroll practices; (ii) monthly severance
payments during the Severance Period equal to 1/12th of the

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Employee's "target bonus" (as defined below) for the fiscal year in which the
termination occurs (or for the prior fiscal year if a target bonus has not yet
been determined for the fiscal year in which the termination occurs); (iii)
continuation of all health and life insurance benefits through the end of the
Severance Period substantially identical to those to which the Employee was
entitled immediately prior to the termination, or to those being offered to
officers of the Company, or a successor corporation, if the Company's benefit
programs are changed during the Severance Period; and (iv) outplacement
services with a total value not to exceed $15,000. For purposes of this
Agreement, the term "target bonus" shall mean the Employee's base salary in
effect on the termination date multiplied by that percentage of such base
salary that is prescribed by the Company under its Executive Bonus Program as
the percentage of such base salary payable to the Employee as a bonus if the
Company pays bonuses at one-hundred percent (100%) of its operating plan.

                 (iii)  Involuntary Termination for Cause.  If the Employee's
                        ---------------------------------
employment is terminated for Cause, then the Employee shall not be entitled to
receive severance payments.  The Employee's benefits will be terminated under
the Company's then existing benefit plans and policies in accordance with such
plans and policies in effect on the date of termination.

              (b) Termination Apart from A Change of Control.  In the event the
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Employee's employment terminates for any reason, either prior to the occurrence
of a Change of Control or after the two year period following the effective date
of a Change of Control, then the Employee shall not be entitled to receive any
severance payments under this Agreement.  The Employee's benefits will be
terminated under the terms of the Employment Agreement and the Company's then
existing benefit plans and policies in accordance with such plans and policies
in effect on the date of termination or as otherwise determined by the Board of
Directors of the Company.

          4.  Definition of Terms.  The following terms referred to in this
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Agreement shall have the following meanings:

               (a) Change of Control.  "Change of Control" shall mean the
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occurrence of any of the following events:

                   (i) Ownership.  Any "Person" (as such term is used in
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Sections 13(d) and 14(d) of the Securities Exchange Act of 1934, as amended)
is or becomes the "Beneficial Owner" (as defined in Rule 13d-3 under said
Act), directly or indirectly, of securities of the Company representing twenty
percent (20%) or more of the total voting power represented by the Company's
then outstanding voting securities without the approval of the Board of
Directors of the Company; or

                   (ii) Merger/Sale of Assets.  A merger or consolidation of
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the Company whether or not approved by the Board of Directors of the Company,
other than a merger or consolidation which would result in the voting
securities of the Company outstanding immediately prior thereto continuing to
represent (either by remaining outstanding or by being converted into voting
securities of the surviving entity) at least fifty

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percent (50%) of the total voting power represented by the voting securities
of the Company or such surviving entity outstanding immediately after such
merger or consolidation, or the stockholders of the Company approve a plan of
complete liquidation of the Company or an agreement for the sale or
disposition by the Company of all or substantially all of the Company's
assets.

                  (iii)  Change in Board Composition.  A change in the
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composition of the Board of Directors of the Company, as a result of which
fewer than a majority of the directors are Incumbent Directors. "Incumbent
Directors" shall mean directors who either (A) are directors of the Company as
of May 6, 1997 or (B) are elected, or nominated for election, to the Board of
Directors of the Company with the affirmative votes of at least a majority of
the Incumbent Directors at the time of such election or nomination (but shall
not include an individual whose election or nomination is in connection with
an actual or threatened proxy contest relating to the election of directors to
the Company).

              (b) Cause.  "Cause" shall mean (i) gross negligence or willful
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misconduct in the performance of the Employee's duties to the Company where such
gross negligence or willful misconduct has resulted or is likely to result in
substantial and material damage to the Company or its subsidiaries, (ii)
repeated unexplained or unjustified absence from the Company, (iii) a material
and willful violation of any federal or state law; (iv) commission of any act of
fraud with respect to the Company; or (v) conviction of a felony or a crime
involving moral turpitude causing material harm to the standing and reputation
of the Company, in each case as determined in good faith by the Board of
Directors of the Company.

              (c) Involuntary Termination.  "Involuntary Termination" shall
                  -----------------------
include any termination by the Company other than for Cause and the Employee's
voluntary termination, upon 30 days prior written notice to the Company,
following (i) a material reduction or change in job duties, responsibilities
and requirements inconsistent with the Employee's position with the Company
and the Employee's prior duties, responsibilities and requirements; (ii) any
reduction of the Employee's base compensation (other than in connection with a
general decrease in base salaries for most similarly situated employees of the
successor corporation); or (iii) the Employee's refusal to relocate to a
location more than 50 miles from the Company's current location.

          5.  Limitation on Payments.  In the event that the severance and other
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benefits provided for in this Agreement to the Employee (i) constitute
"parachute payments" within the meaning of Section 280G of the Internal Revenue
Code of 1986, as amended (the "Code") and (ii) but for this Section, would be
subject to the excise tax imposed by Section 4999 of the Code, then the
Employee's benefits under Sections 2 and 3(a)(ii) shall be payable either:

               (a)  in full, or

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               (b) as to such lesser amount which would result in no portion
of such severance benefits being subject to excise tax under Section 4999 of
the Code, whichever of the foregoing amounts, taking into account the
applicable federal, state and local income taxes and the excise tax imposed by
Section 4999, results in the receipt by the Employee on an after-tax basis, of
the greatest amount of benefits under Sections 2 and 3(a)(ii), notwithstanding
that all or some portion of such benefits may be taxable under Section 4999 of
the Code. Unless the Company and the Employee otherwise agree in writing, any
determination required under this Section 5 shall be made in writing by the
Company's independent public accountants (the "Accountants"), whose
determination shall be conclusive and binding upon the Employee and the
Company for all purposes. For purposes of making the calculations required by
this Section 5, the Accountants may make reasonable assumptions and
approximations concerning applicable taxes and may rely on reasonable, good
faith interpretations concerning the application of Section 280G and 4999 of
the Code. The Company and the Employee shall furnish to the Accountants such
information and documents as the Accountants may reasonably request in order
to make a determination under this Section. The Company shall bear all costs
the Accountants may reasonably incur in connection with any calculations
contemplated by this Section 5.

          6.  Certain Business Combinations.  In the event it is determined by
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the Board, upon consultation with Company management and the Company's
independent auditors, that the enforcement of any Section of this Agreement,
including, but not limited to, Section 2 hereof, which allows for the
acceleration of vesting of Option shares upon the effective date of a Change of
Control, would preclude accounting for any proposed business combination of the
Company involving a Change of Control as a pooling of interests, and the Board
otherwise desires to approve such a proposed business transaction which requires
as a condition to the closing of such transaction that it be accounted for as a
pooling of interests, then any such Section of this Agreement shall be null and
void.  For purposes of this Section 6, the Board's determination shall require
the unanimous approval of the non-employee Board members.

          7.  Successors.  Any successor to the Company (whether direct or
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indirect and whether by purchase, lease, merger, consolidation, liquidation or
otherwise) to all or substantially all of the Company's business and/or assets
shall assume the obligations under this Agreement and agree expressly to perform
the obligations under this Agreement in the same manner and to the same extent
as the Company would be required to perform such obligations in the absence of a
succession.  The terms of this Agreement and all of the Employee's rights
hereunder shall inure to the benefit of, and be enforceable by, the Employee's
personal or legal representatives, executors, administrators, successors, heirs,
distributees, devisees and legatees.

          8.  Notice.  Notices and all other communications contemplated by this
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Agreement shall be in writing and shall be deemed to have been duly given when
personally delivered or when mailed by U.S. registered or certified mail, return
receipt requested and postage prepaid.  Mailed notices to the Employee shall be
addressed to the Employee at the

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home address which the Employee most recently communicated to the Company in
writing. In the case of the Company, mailed notices shall be addressed to its
corporate headquarters, and all notices shall be directed to the attention of
its Secretary.

          9.  Miscellaneous Provisions.
              ------------------------

              (a) No Duty to Mitigate.  The Employee shall not be required to
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mitigate the amount of any payment contemplated by this Agreement (whether by
seeking new employment or in any other manner), nor, except as otherwise
provided in this Agreement, shall any such payment be reduced by any earnings
that the Employee may receive from any other source.

              (b) Waiver.  No provision of this Agreement shall be modified,
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waived or discharged unless the modification, waiver or discharge is agreed to
in writing and signed by the Employee and by an authorized officer of the
Company (other than the Employee). No waiver by either party of any breach of,
or of compliance with, any condition or provision of this Agreement by the
other party shall be considered a waiver of any other condition or provision
or of the same condition or provision at another time.

              (c) Whole Agreement.  No agreements, representations or
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understandings (whether oral or written and whether express or implied) which
are not expressly set forth in this Agreement have been made or entered into
by either party with respect to the subject matter hereof. This Agreement
supersedes any agreement of the same title and concerning similar subject
matter dated prior to the date of this Agreement, and by execution of this
Agreement both parties agree that any such predecessor agreement shall be
deemed null and void.

              (d) Choice of Law.  The validity, interpretation, construction and
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performance of this Agreement shall be governed by the laws of the State of
California without reference to conflict of laws provisions.

              (e) Severability.  If any term or provision of this Agreement
                  ------------
or the application thereof to any circumstance shall, in any jurisdiction and
to any extent, be invalid or unenforceable, such term or provision shall be
ineffective as to such jurisdiction to the extent of such invalidity or
unenforceability without invalidating or rendering unenforceable the remaining
terms and provisions of this Agreement or the application of such terms and
provisions to circumstances other than those as to which it is held invalid or
unenforceable, and a suitable and equitable term or provision shall be
substituted therefor to carry out, insofar as may be valid and enforceable,
the intent and purpose of the invalid or unenforceable term or provision.

              (f) Arbitration.  Any dispute or controversy arising under or in
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connection with this Agreement may be settled at the option of either party by
binding arbitration in the County of Contra Costa, California, in accordance
with the rules of the American Arbitration Association then in effect.  Judgment
may be entered on the arbitrator's  award in any court having jurisdiction.
Punitive damages shall not be awarded.

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              (g) Legal Fees and Expenses.  The parties shall each bear their
                  -----------------------
own expenses, legal fees and other fees incurred in connection with this
Agreement.

              (h) No Assignment of Benefits.  The rights of any person to
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payments or benefits under this Agreement shall not be made subject to option
or assignment, either by voluntary or involuntary assignment or by operation
of law, including (without limitation) bankruptcy, garnishment, attachment or
other creditor's process, and any action in violation of this subsection (h)
shall be void.

              (i) Employment Taxes.  All payments made pursuant to this
                  ----------------
Agreement will be subject to withholding of applicable income and employment
taxes.

              (j) Assignment by Company.  The Company may assign its rights
                  ---------------------
under this Agreement to an affiliate, and an affiliate may assign its rights
under this Agreement to another affiliate of the Company or to the Company;
provided, however, that no assignment shall be made if the net worth of the
assignee is less than the net worth of the Company at the time of assignment.
In the case of any such assignment, the term "Company" when used in a section
of this Agreement shall mean the corporation that actually employs the
Employee.

              (k) Counterparts.  This Agreement may be executed in counterparts,
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each of which shall be deemed an original, but all of which together will
constitute one and the same instrument.

     IN WITNESS WHEREOF, each of the parties has executed this Agreement, in the
case of the Company by its duly authorized officer, as of the day and year first
above written.



KERAVISION, INC.                    THOMAS M. LOARIE


BY:   /s/ Mark Fischer-Colbrie      /s/  Thomas M. Loarie
      ------------------------      ---------------------

TITLE:  Vice President, Finance
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