Document:

<PAGE>

                                                                    Exhibit 10.3

                                   AMENDMENT
                          Dated as of August 15, 2000

          This AMENDMENT (this "Amendment") is among KeraVision, Inc., a
Delaware corporation (the "Company"), and Thomas M. Loarie (the "Employee").

                            PRELIMINARY STATEMENTS:

          1.  The Company and the Employee have entered into a Change Of Control
Agreement, dated as of May 6, 1997 (the "Agreement"; capitalized terms used and
not otherwise defined herein have the meanings assigned to such terms in the
Agreement).

          2.  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.

          3.  The Employee has previously issued those Promissory Notes set
forth on Schedule A attached hereto (the "Promissory Notes").

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

          SECTION 1.  Amendment to Agreement.  Effective as of the date hereof,
and in accordance with Section 9(b) of the Agreement, the Company and the
Employee hereby agree to the following amendment to the Agreement:

          Section 2 of the Agreement is hereby revised in its entirety to read
as follows:

          "Stock Options and Promissory Notes.

          (a)  Stock Options.  Subject to Sections 5 and 6 below, in the event
     of 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 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.

          (b)  Promissory Notes.  Subject to Sections 5 and 6 below, in the
     event of a Change of Control and regardless of whether Employee's
     employment with the Company is terminated in connection with such Change of
     Control, all amounts due to the Company, including accrued interest,
     pursuant to the terms and conditions of the Promissory Notes shall be
     forgiven in their entirety."
<PAGE>

          SECTION 2.  Reference to and Effect on Agreement.  (a) Upon and after
the effectiveness of this Amendment, each reference in the Agreement to "this
Agreement", "hereunder", "hereof" or words of like import referring to the
Agreement, and each reference in any other documents to "the Change of Control
Agreement", "thereunder", "thereof" or words of like import referring to the
Agreement, shall mean and be a reference to the Agreement as modified hereby.

          (b) Except as specifically modified above, the Agreement is and shall
continue to be in full force and effect and is hereby in all respects ratified
and confirmed.

          SECTION 3.  Counterparts.  This Agreement may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which when so executed and delivered shall be deemed to be an original
and all of which taken together shall constitute but one and the same agreement.
Delivery of an executed counterpart of a signature page to this Agreement by
facsimile shall be effective as delivery of a manually executed counterpart of
this Agreement.

          SECTION 4.  Severability.  Any provision of this Agreement that is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

                            [Signature Page Follows]

                                       2
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed as of the date first written above.

                                 KERAVISION, INC.,
                                 a Delaware corporation

                                 By:  /s/ Mark Fischer-Colbrie
                                      ----------------------------------------
                                      Name:  Mark Fischer-Colbrie
                                            ----------------------------------
                                      Title: VP Finance and CFO
                                            ----------------------------------

                                 EMPLOYEE

                                 By:    /s/ Thomas M. Loarie
                                        --------------------------------------
                                        Name:  Thomas M. Loarie
                                             ---------------------------------
                                        Title: Chairman and CEO
                                             ---------------------------------
<PAGE>

                                   SCHEDULE A

                                PROMISSORY NOTES

<TABLE>
<CAPTION>

                                AGGREGATE PRINCIPAL AMOUNT AND     NUMBER OF SHARES OF COMMON
       DATE OF ISSUANCE            INTEREST AT JULY 31, 2000            STOCK AS SECURITY
------------------------------------------------------------------------------------------------
<S>                             <C>                              <C>
October 30, 1991                         $231,984.66                        212,685
April 12, 1993                            110,249.99                         42,193
November 7, 1993                          158,916.97                         60,000
April 1, 1998                              62,950.32                           N/A
April 1, 1998                              22,406.05                           N/A
September 1, 1998                         318,727.15                           N/A
                                  -----------------------
     Total:                              $905,235.14
                                  ======================
</TABLE>

                                       2<PAGE>

                                                                    Exhibit 10.4

                                   AMENDMENT
                          Dated as of August 15, 2000

          This AMENDMENT (this "Amendment") is among KeraVision, Inc., a
Delaware corporation (the "Company"), Thomas A. Silvestrini (the "Employee").

                            PRELIMINARY STATEMENTS:

          1.  The Company and the Employee have entered into a Change Of Control
Agreement, dated as of May 6, 1997 (the "Agreement"; capitalized terms used and
not otherwise defined herein have the meanings assigned to such terms in the
Agreement).

          2.  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.

          3.  The Employee has previously issued those Promissory Notes set
forth on Schedule A attached hereto (the "Promissory Notes").

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

          SECTION 1.  Amendment to Agreement.  Effective as of the date hereof,
and in accordance with Section 9(b) of the Agreement, the Company and the
Employee hereby agree to the following amendment to the Agreement:

          Section 2 of the Agreement is hereby revised in its entirety to read
as follows:

          "Stock Options and Promissory Notes.

          (a)  Hostile Takeover.  Subject to Sections 5 and 6 below, in the
     event of a Hostile Takeover and regardless of whether the Employee's
     employment with the company is terminated in connection with the Hostile
     Takeover, each stock option granted for the Company's securities (the
     "Option") held by the Employee shall become fully vested and immediately
     exercisable on the effective date of the transaction 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.

          (b)  Change of Control.  Subject to Sections 5 and 6 below, in the
     event of 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 Option held by the Employee shall become vested on the
     effective date of the transaction as to fifty percent (50%) of the Option
     shares that have not otherwise vested as of such date.  The Option shares
     that remain unvested as of the effective date of the transaction shall
<PAGE>

     thereafter vest at the same rate (that is, the same number of shares shall
     vest during each vesting period) that was in effect prior to the Change of
     Control, and shall accordingly vest over a period that is one-half of the
     total vesting period that would otherwise be then remaining under the terms
     of the Option Agreement pursuant to which each such Option was granted.

          (c)  Promissory Notes.  Subject to Sections 5 and 6 below, in the
     event of a Change of Control or a Hostile Takeover and regardless of
     whether Employee's employment with the Company is terminated in connection
     with such Change of Control or Hostile Takeover, as the case may be, all
     amounts due to the Company, including accrued interest, pursuant to the
     terms and conditions of the Promissory Notes shall be forgiven in their
     entirety.".

          SECTION 2.  Reference to and Effect on Agreement.  (a)  Upon and after
the effectiveness of this Amendment, each reference in the Agreement to "this
Agreement", "hereunder", "hereof" or words of like import referring to the
Agreement, and each reference in any other documents to "the Change of Control
Agreement", "thereunder", "thereof" or words of like import referring to the
Agreement, shall mean and be a reference to the Agreement as modified hereby.

          (b) Except as specifically modified above, the Agreement is and shall
continue to be in full force and effect and is hereby in all respects ratified
and confirmed.

          SECTION 3.  Counterparts.  This Agreement may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which when so executed and delivered shall be deemed to be an original
and all of which taken together shall constitute but one and the same agreement.
Delivery of an executed counterpart of a signature page to this Agreement by
facsimile shall be effective as delivery of a manually executed counterpart of
this Agreement.

          SECTION 4.  Severability.  Any provision of this Agreement that is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

                            [Signature Page Follows]

                                       2
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed as of the date first written above.

                                 KERAVISION, INC.,
                                 a Delaware corporation

                                 By:    /s/Thomas M. Loarie
                                    ---------------------------------
                                    Name:  Thomas M. Loarie
                                         ----------------------------
                                    Title:  Chairman and CEO
                                          ---------------------------

                                 EMPLOYEE

                                 By:    /s/Thomas A. Silvestrini
                                    ---------------------------------
                                    Name:    Thomas A. Silvestrini
                                         ----------------------------
                                    Title:  VP Research & Development
                                          ---------------------------
<PAGE>

                                   SCHEDULE A

                                PROMISSORY NOTES

<TABLE>
<CAPTION>

                                AGGREGATE PRINCIPAL AMOUNT AND     NUMBER OF SHARES OF COMMON
       DATE OF ISSUANCE            INTEREST AT JULY 31, 2000            STOCK AS SECURITY
------------------------------------------------------------------------------------------------
<S>                             <C>                              <C>
October 30, 1991                          $ 37,137.58                        34,048
April 1, 1998                               94,172.96                          N/A
September 1, 1998                           84,457.06                          N/A
November 7, 1993                           158,916.97                        60,000
                                  ---------------------------
     Total:                               $374,684.57
                                  ===========================
</TABLE>

                                       2
<PAGE>

                                   AMENDMENT
                          Dated as of August 15, 2000

          This AMENDMENT (this "Amendment") is among KeraVision, Inc., a
Delaware corporation (the "Company"), Mark Fischer-Colbrie (the "Employee").

                            PRELIMINARY STATEMENTS:

          1.  The Company and the Employee have entered into a Change Of Control
Agreement, dated as of May 6, 1997 (the "Agreement"; capitalized terms used and
not otherwise defined herein have the meanings assigned to such terms in the
Agreement).

          2.  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.

          3.  The Employee has previously issued those Promissory Notes set
forth on Schedule A attached hereto (the "Promissory Notes").

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

          SECTION 1.  Amendment to Agreement.  Effective as of the date hereof,
and in accordance with Section 9(b) of the Agreement, the Company and the
Employee hereby agree to the following amendment to the Agreement:

          Section 2 of the Agreement is hereby revised in its entirety to read
as follows:

          "Stock Options and Promissory Notes.

          (a)  Hostile Takeover.  Subject to Sections 5 and 6 below, in the
     event of a Hostile Takeover and regardless of whether the Employee's
     employment with the company is terminated in connection with the Hostile
     Takeover, each stock option granted for the Company's securities (the
     "Option") held by the Employee shall become fully vested and immediately
     exercisable on the effective date of the transaction 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.

          (b)  Change of Control.  Subject to Sections 5 and 6 below, in the
     event of 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 Option held by the Employee shall become vested on the
     effective date of the transaction as to fifty percent (50%) of the Option
     shares that have not otherwise vested as of such date.  The Option shares
     that remain unvested as of the effective date of the transaction shall
<PAGE>

     thereafter vest at the same rate (that is, the same number of shares shall
     vest during each vesting period) that was in effect prior to the Change of
     Control, and shall accordingly vest over a period that is one-half of the
     total vesting period that would otherwise be then remaining under the terms
     of the Option Agreement pursuant to which each such Option was granted.

          (c)  Promissory Notes.  Subject to Sections 5 and 6 below, in the
     event of a Change of Control or a Hostile Takeover and regardless of
     whether Employee's employment with the Company is terminated in connection
     with such Change of Control or Hostile Takeover, as the case may be, all
     amounts due to the Company, including accrued interest, pursuant to the
     terms and conditions of the Promissory Notes shall be forgiven in their
     entirety.".

          SECTION 2.  Reference to and Effect on Agreement.  (a)  Upon and after
the effectiveness of this Amendment, each reference in the Agreement to "this
Agreement", "hereunder", "hereof" or words of like import referring to the
Agreement, and each reference in any other documents to "the Change of Control
Agreement", "thereunder", "thereof" or words of like import referring to the
Agreement, shall mean and be a reference to the Agreement as modified hereby.

          (b) Except as specifically modified above, the Agreement is and shall
continue to be in full force and effect and is hereby in all respects ratified
and confirmed.

          SECTION 3.  Counterparts.  This Agreement may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which when so executed and delivered shall be deemed to be an original
and all of which taken together shall constitute but one and the same agreement.
Delivery of an executed counterpart of a signature page to this Agreement by
facsimile shall be effective as delivery of a manually executed counterpart of
this Agreement.

          SECTION 4.  Severability.  Any provision of this Agreement that is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

                            [Signature Page Follows]

                                       2
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed as of the date first written above.

                                 KERAVISION, INC.,
                                 a Delaware corporation

                                 By:    /s/Thomas M. Loarie
                                    -----------------------------
                                    Name:  Thomas M. Loarie
                                         ------------------------
                                    Title:  Chairman & CEO
                                          -----------------------

                                 EMPLOYEE

                                 By:    /s/Mark Fischer-Colbrie
                                    -----------------------------
                                    Name:    Mark Fischer-Colbrie
                                         ------------------------
                                    Title:  VP Finance and CFO
                                          -----------------------
<PAGE>

                                   SCHEDULE A

                                PROMISSORY NOTES

<TABLE>
<CAPTION>

                                AGGREGATE PRINCIPAL AMOUNT AND     NUMBER OF SHARES OF COMMON
       DATE OF ISSUANCE            INTEREST AT JULY 31, 2000            STOCK AS SECURITY
------------------------------------------------------------------------------------------------
<S>                             <C>                              <C>
November 7, 1993                         $ 18,370.07                         15,000
April 1, 1998                             107,741.35                           N/A
September 1, 1998                          57,644.05                           N/A
                                 ---------------------------
     Total:                              $183,755.47
                                 ===========================
</TABLE>

                                       2
<PAGE>

                                   AMENDMENT
                          Dated as of August 15, 2000

          This AMENDMENT (this "Amendment") is among KeraVision, Inc., a
Delaware corporation (the "Company"), Darlene Crockett-Billig (the "Employee").

                            PRELIMINARY STATEMENTS:

          1.  The Company and the Employee have entered into a Change Of Control
Agreement, dated as of May 6, 1997 (the "Agreement"; capitalized terms used and
not otherwise defined herein have the meanings assigned to such terms in the
Agreement).

          2.  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.

          3.  The Employee has previously issued those Promissory Notes set
forth on Schedule A attached hereto (the "Promissory Notes").

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

          SECTION 1.  Amendment to Agreement.  Effective as of the date hereof,
and in accordance with Section 9(b) of the Agreement, the Company and the
Employee hereby agree to the following amendment to the Agreement:

          Section 2 of the Agreement is hereby revised in its entirety to read
as follows:

          "Stock Options and Promissory Notes.

          (a)  Hostile Takeover.  Subject to Sections 5 and 6 below, in the
     event of a Hostile Takeover and regardless of whether the Employee's
     employment with the company is terminated in connection with the Hostile
     Takeover, each stock option granted for the Company's securities (the
     "Option") held by the Employee shall become fully vested and immediately
     exercisable on the effective date of the transaction 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.

          (b)  Change of Control.  Subject to Sections 5 and 6 below, in the
     event of 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 Option held by the Employee shall become vested on the
     effective date of the transaction as to fifty percent (50%) of the Option
     shares that have not otherwise vested as of such date.  The Option shares
     that remain unvested as of the effective date of the transaction shall
<PAGE>

     thereafter vest at the same rate (that is, the same number of shares shall
     vest during each vesting period) that was in effect prior to the Change of
     Control, and shall accordingly vest over a period that is one-half of the
     total vesting period that would otherwise be then remaining under the terms
     of the Option Agreement pursuant to which each such Option was granted.

          (c)  Promissory Notes.  Subject to Sections 5 and 6 below, in the
     event of a Change of Control or a Hostile Takeover and regardless of
     whether Employee's employment with the Company is terminated in connection
     with such Change of Control or Hostile Takeover, as the case may be, all
     amounts due to the Company, including accrued interest, pursuant to the
     terms and conditions of the Promissory Notes shall be forgiven in their
     entirety.".

          SECTION 2.  Reference to and Effect on Agreement.  (a)  Upon and after
the effectiveness of this Amendment, each reference in the Agreement to "this
Agreement", "hereunder", "hereof" or words of like import referring to the
Agreement, and each reference in any other documents to "the Change of Control
Agreement", "thereunder", "thereof" or words of like import referring to the
Agreement, shall mean and be a reference to the Agreement as modified hereby.

          (b) Except as specifically modified above, the Agreement is and shall
continue to be in full force and effect and is hereby in all respects ratified
and confirmed.

          SECTION 3.  Counterparts.  This Agreement may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which when so executed and delivered shall be deemed to be an original
and all of which taken together shall constitute but one and the same agreement.
Delivery of an executed counterpart of a signature page to this Agreement by
facsimile shall be effective as delivery of a manually executed counterpart of
this Agreement.

          SECTION 4.  Severability.  Any provision of this Agreement that is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

                            [Signature Page Follows]

                                       2
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed as of the date first written above.

                                 KERAVISION, INC.,
                                 a Delaware corporation

                                 By:    /s/Thomas M. Loarie
                                    --------------------------------
                                    Name:  Thomas M. Loarie
                                         ---------------------------
                                    Title:  Chairman & CEO
                                          --------------------------

                                 EMPLOYEE

                                 By:    /s/Darlene Crockett-Billig
                                    --------------------------------
                                    Name:    Darlene Crockett-Billig
                                         ---------------------------

<PAGE>

                                   SCHEDULE A

                                PROMISSORY NOTES

<TABLE>
<CAPTION>

                                AGGREGATE PRINCIPAL AMOUNT AND     NUMBER OF SHARES OF COMMON
       DATE OF ISSUANCE            INTEREST AT JULY 31, 2000            STOCK AS SECURITY
------------------------------------------------------------------------------------------------
<S>                             <C>                              <C>
November 7, 1993                           $105,944.64                       40,000
September 1, 1998                            91,935.30                         N/A
                                   --------------------------
     Total:                                $197,879.94
</TABLE>

                                       2

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00017-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00017-of-00352.parquet"}]]