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                                                                     Exhibit 4.3

                                 EYEONICS, INC.

                 AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT

                               DECEMBER 30, 2005

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                                TABLE OF CONTENTS

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                                                                           PAGE
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1. Certain Definitions.................................................      1

   1.1  "Commission"...................................................      1
   1.2  "Holder".......................................................      1
   1.3  "Initiating Holders"...........................................      1
   1.4  "Registrable Securities".......................................      1
   1.5  The terms "register," "registered" and "registration"..........      2
   1.6  "Registration Expenses"........................................      2
   1.7  "Restricted Securities"........................................      2
   1.8  "Securities Act"...............................................      2
   1.9  "Selling Expenses".............................................      2
   1.10 "Shares".......................................................      2

2. Transferability.....................................................      2

   2.1  Restrictions on Transferability................................      2
   2.2  Restrictive Legend.............................................      2
   2.3  Notice of Proposed Transfers...................................      3
   2.4  Removal of Restrictions on Transfer of Securities..............      3

3. Registration Rights.................................................      4

   3.1  Requested Registration.........................................      4
   3.2  Company Registration...........................................      6
   3.3  Registration on Form S-3.......................................      7
   3.4  Expenses of Registration.......................................      8
   3.5  Registration Procedures........................................      8
   3.6  Indemnification................................................     10
   3.7  Information by Holder..........................................     12
   3.8  Rule 144 Reporting.............................................     12
   3.9  Transfer of Registration Rights................................     13
   3.10 Standoff Agreement.............................................     13
   3.11 Termination of Registration Rights.............................     13

4. Right of First Offer................................................     14

   4.1  Right of First Offer Upon Issuances of Securities by the
      Company..........................................................     14

5. Covenants of the Company............................................     15

   5.1  Financial Information..........................................     15
   5.2  Positive Covenants.............................................     16
   5.3  Observer Rights................................................     17
   5.4  Confidentiality................................................     17
   5.5  Redemption.....................................................     18
   5.6  Termination of Covenants.......................................     18
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6. General Provisions..................................................     18

   6.1  Amendment and Waiver...........................................     18
   6.2  Governing Law..................................................     18
   6.3  Successors and Assigns.........................................     18
   6.4  Severability...................................................     18
   6.5  Notices........................................................     18
   6.6  Counterparts...................................................     18
   6.7  Titles and Subtitles...........................................     19
   6.8  Expenses.......................................................     19
   6.9  Aggregation of Stock...........................................     19
   6.10 Entire Agreement...............................................     19
   6.11 Aggregation....................................................     19
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                                      -ii-
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                 AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT

     This Investor Rights Agreement ("Agreement") is entered into as of December
30, 2005 by and among Eyeonics, Inc., a Delaware corporation (the "Company") and
the investors set forth on Schedule A hereto (the "Investors").

     A.   The Company and certain of the Investors have entered into an Amended
          and Restated Investor Rights Agreement dated as of April 10, 2003 (the
          "Previous Investor Rights Agreement").

     B.   The Company and the Investors desire to amend and restate and replace
          in its entirety the Previous Investor Rights Agreement with the terms
          and conditions of this Agreement.

     C.   Certain of the Investors and the Company have entered into a Series E
          Preferred Stock Purchase Agreement (the "Series E Agreement") of even
          date with this Agreement.

     D.   In order to induce the Investors to consummate their purchase of
          Series E Preferred Stock of the Company, the parties have agreed to
          enter into this Agreement upon the terms and conditions set forth
          below. All terms not otherwise defined in this Agreement shall have
          the meaning set forth in the Series E Agreement.

     1. Certain Definitions. As used in this Agreement, the following terms
shall have the following respective meanings:

          1.1 "Commission" shall mean the Securities and Exchange Commission or
any other federal agency at the time administering the Securities Act.

          1.2 "Holder" shall mean the Investors holding Registrable Securities
and any person holding such securities to whom the rights under this Agreement
have been transferred in accordance with Section 3.9 hereof.

          1.3 "Initiating Holders" shall mean any Holder or Holders who in the
aggregate hold at least forty percent (40%) of the Registrable Securities.

          1.4 "Registrable Securities" means (1) any shares of Common Stock held
by the Investors during the term hereof, including any shares of Common Stock
issuable or issued upon conversion of the Shares or any other convertible
securities held by the Investors from time to time during the term hereof and
(2) any Common Stock of the Company issued as (or issuable upon the conversion
or exercise of any warrant, right or other security which is issued as) a
dividend or other distribution with respect to, or in exchange for or in
replacement of, the shares referenced in (1) above, excluding in all cases,
however, (i) any Registrable Securities sold by a person in a transaction in
which such person's rights under this Agreement are not assigned, or (ii) any
Registrable Securities sold to or through a broker or dealer or underwriter in a
public distribution or a public securities transaction.

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          1.5 The terms "register," "registered" and "registration" refer to a
registration effected by preparing and filing a registration statement in
compliance with the Securities Act, and the declaration or ordering of the
effectiveness of such registration statement.

          1.6 "Registration Expenses" shall mean all expenses, except Selling
Expenses as defined below, incurred by the Company in complying with Sections
3.1, 3.2 and 3.3 hereof, including, without limitation, all registration,
qualification and filing fees, printing expenses, escrow fees, fees and
disbursements of counsel for the Company, blue sky fees and expenses, the
expense of any special audits incident to or required by any such registration
(but excluding the compensation of regular employees of the Company which shall
be paid in any event by the Company).

          1.7 "Restricted Securities" shall mean the securities of the Company
required to bear the legend set forth in Section 2.2 hereof.

          1.8 "Securities Act" shall mean the Securities Act of 1933, as
amended, or any similar federal statute and the rules and regulations of the
Commission thereunder, all as the same shall be in effect at the time.

          1.9 "Selling Expenses" shall mean all underwriting discounts, selling
commissions, stock transfer taxes and costs of special counsel to the Holders,
if any, applicable to the securities registered by the Holders.

          1.10 "Shares" shall mean the Company's Series B, C , D and E Preferred
Stock.

     2. Transferability.

          2.1 Restrictions on Transferability. The Shares and the Registrable
Securities shall not be sold, assigned, transferred or pledged except upon the
conditions specified in this Section 2, which conditions are intended to ensure
compliance with the provisions of the Securities Act. The Investors will cause
any proposed purchaser, assignee, transferee, or pledgee of the Shares or the
Registrable Securities held by the Investors to agree to take and hold such
securities subject to the provisions and upon the conditions specified in this
Section 2.

          2.2 Restrictive Legend. Each certificate representing (i) the Shares,
(ii) the Registrable Securities and (iii) any other securities issued in respect
of the Shares or the Registrable Securities upon any stock split, stock
dividend, recapitalization, merger, consolidation or similar event, shall
(unless otherwise permitted by the provisions of Section 2.3 below) be stamped
or otherwise imprinted with legends in the following forms (in addition to any
legend required under applicable state securities laws):

               (a)  THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER
                    THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD
                    OR TRANSFERRED, ASSIGNED, PLEDGED OR HYPOTHECATED UNLESS AND

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                    UNTIL REGISTERED UNDER SUCH ACT OR UNLESS THE COMPANY HAS
                    RECEIVED AN OPINION OF COUNSEL OR OTHER EVIDENCE,
                    SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH
                    REGISTRATION IS NOT REQUIRED.

               (b)  THE SHARES REPRESENTED BY THIS CERTIFICATE MAY BE
                    TRANSFERRED ONLY IN ACCORDANCE WITH THE TERMS OF AN
                    AGREEMENT BETWEEN THE COMPANY AND THE STOCKHOLDER, A COPY OF
                    WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY.

     The Investors and Holders consent to the Company making a notation on its
records and giving instructions to any transfer agent of the Shares or the
Registrable Securities in order to implement the restrictions on transfer
established in this Section 2.

          2.3 Notice of Proposed Transfers. The holder of each certificate
representing Restricted Securities by acceptance thereof agrees to comply in all
respects with the provisions of this Section 2.3. Prior to any proposed sale,
assignment, transfer or pledge of any Restricted Securities (other than (i) a
transfer not involving a change in beneficial ownership, or (ii) in transactions
involving the distribution without consideration of Restricted Securities by the
Investors to any of its partners, or retired partners, or to the estate of any
of its partners or retired partners or (iii) a transfer to an affiliated fund,
partnership or company, which is not a competitor of the Company, subject to
compliance with applicable securities laws), unless there is in effect a
registration statement under the Securities Act covering the proposed transfer,
the holder thereof shall give written notice to the Company of such holder's
intention to effect such transfer, sale, assignment or pledge. Each such notice
shall describe the manner and circumstances of the proposed transfer, sale,
assignment or pledge in sufficient detail, and shall be accompanied, at such
holder's expense by either (i) an unqualified written opinion of legal counsel
who shall, and whose legal opinion shall be, reasonably satisfactory to the
Company addressed to the Company, to the effect that the proposed transfer of
the Restricted Securities may be effected without registration under the
Securities Act, or (ii) a "no action" letter from the Commission to the effect
that the transfer of such securities without registration will not result in a
recommendation by the staff of the Commission that action be taken with respect
thereto, whereupon the holder of such Restricted Securities shall be entitled to
transfer such Restricted Securities in accordance with the terms of the notice
delivered by the holder to the Company. Each certificate evidencing the
Restricted Securities transferred as above provided shall bear the appropriate
restrictive legend set forth in Section 2.2 above, except that such certificate
shall not bear such restrictive legend if in the opinion of counsel for such
holder and in the reasonable opinion of the Company such legend is not required
in order to establish compliance with any provision of the Securities Act.

          2.4 Removal of Restrictions on Transfer of Securities. Any legend
referred to in Section 2.2 hereof stamped on a certificate evidencing (i) the
Shares, (ii) the Registrable Securities or (iii) any other securities issued in
respect of the Shares or the Registrable Securities upon any stock split, stock
dividend, recapitalization, merger, consolidation or similar event and the stock
transfer instructions and record notations with respect to such security shall
be removed and the

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Company shall issue a certificate without such legend to the holder of such
security if such security is registered under the Securities Act, or if such
holder provides the Company with an opinion of counsel (which may be counsel for
the Company) reasonably acceptable to the Company to the effect that a public
sale or transfer of such security may be made without qualification, legend, or
registration under the Securities Act.

     3. Registration Rights.

          3.1 Requested Registration.

               (a) Requested Registration. If the Company shall receive from
Initiating Holders a written request that the Company effect any registration
(other than a registration on Form S-3 or any related form of registration
statement) with respect to Registrable Securities representing at least forty
percent (40%) of the Registrable Securities (or any lesser percentage if the
anticipated aggregate offering price to the public, excluding underwriting
discounts and commissions, is at least seven million five hundred thousand
dollars ($7,500,000)), the Company will:

                    (i) within thirty (30) days of the receipt by the Company of
such notice, give written notice of the proposed registration, qualification or
compliance to all other Holders; and

                    (ii) as soon as practicable, use its best efforts to effect
such registration, qualification or compliance (including, without limitation,
appropriate qualification under applicable blue sky or other state securities
laws and appropriate compliance with applicable regulations issued under the
Securities Act and any other governmental requirements or regulations) as may be
so requested and as would permit or facilitate the sale and distribution of all
or such portion of such Registrable Securities as are specified in such request,
together with all or such portion of the Registrable Securities of any Holder or
Holders joining in such request as are specified in a written request received
by the Company within twenty (20) days after receipt of such written notice from
the Company;

     Provided, however, that the Company shall not be obligated to take any
action to effect any such registration, qualification or compliance pursuant to
this Section 3.1:

                         (A) In any particular jurisdiction in which the Company
would be required to execute a general consent to service of process in
effecting such registration, qualification or compliance unless the Company is
already subject to service in such jurisdiction and except as may be required by
the Securities Act;

                         (B) Prior to six (6) months following the closing date
of the Company's initial underwritten public offering pursuant to an effective
registration statement under the Securities Act;

                         (C) If the Company's Common Stock is not listed on a
national securities exchange (as defined in the Securities Exchange Act of 1934)
and the Initiating Holders do not request that such offering be firmly
underwritten by underwriters selected by the Company (subject to the consent of
the Holders, which consent shall not be unreasonably withheld);

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                         (D) During the period starting with the date sixty (60)
days prior to the Company's estimated date of filing of, and ending on the date
three (3) months immediately following the effective date of, any registration
statement pertaining to securities of the Company (other than a registration of
securities in a Rule 145 transaction or with respect to an employee benefit
plan), provided that the Company is actively employing in good faith all
reasonable efforts to cause such registration statement to become effective;

                         (E) After the Company has effected two (2) such
registrations pursuant to this Section 3.1(a) (counting for this purpose only
registrations which have been declared or ordered effective and registrations
which have been withdrawn by the Holders as to which the Holders have not
elected to bear the Registration Expenses);

                         (F) If the Initiating Holders propose to dispose of
shares of Registrable Securities which may be immediately registered on Form S-3
pursuant to a request under Section 3.3 hereof;

                         (G) If the Company shall furnish to such Holders a
certificate signed by the President of the Company stating that in the good
faith judgment of the Board of Directors it would be seriously detrimental to
the Company or its stockholders for a registration statement to be filed in the
near future, then the Company's obligation to use its best efforts to register,
qualify or comply under this Section 3.1 shall be deferred for a period not to
exceed ninety (90) days from the date of receipt of written request from the
Initiating Holders; provided, however, that the Company shall not exercise such
right more than once in any twelve-month period.

     Subject to the foregoing clauses (A) through (G), the Company shall file a
registration statement covering the Registrable Securities so requested to be
registered as soon as practicable, after receipt of the request or requests of
the Initiating Holders.

               (b) Underwriting. In the event that a registration pursuant to
Section 3.1 is for a registered public offering involving an underwriting, the
Company shall so advise the Holders as part of the notice given pursuant to
Section 3.1(a)(i). In such event, the right of any Holder to registration
pursuant to Section 3.1 shall be conditioned upon such Holder's participation in
the underwriting arrangements required by this Section 3.1, and the inclusion of
such Holder's Registrable Securities in the underwriting to the extent requested
shall be limited to the extent provided herein.

     The Company shall (together with all Holders proposing to distribute their
securities through such underwriting) enter into an underwriting agreement in
customary form with the managing underwriter of recognized national standing
selected for such underwriting by the Company and reasonably acceptable to a
majority of the Holders proposing to distribute their securities through such
underwriting. Notwithstanding any other provision of this Section 3.1, if the
managing underwriter advises the Initiating Holders in writing that marketing
factors require a limitation of the number of shares to be underwritten, then
the Company shall so advise all holders of Registrable Securities and the number
of shares of Registrable Securities that may be included in the registration and
underwriting shall be allocated among all Holders thereof in proportion, as
nearly as practicable,

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to the respective amounts of Registrable Securities held by such Holders at the
time of filing the registration statement or in such other manner as shall be
agreed to by the Company and Holders of a majority of the Registrable Securities
proposed to be included in such registration. No Registrable Securities excluded
from the underwriting by reason of the underwriter's marketing limitation shall
be included in such registration. To facilitate the allocation of shares in
accordance with the above provisions, the Company or the underwriters may round
the number of shares allocated to any Holder to the nearest one hundred (100)
shares.

     If any Holder of Registrable Securities disapproves of the terms of the
underwriting, such Holder may elect to withdraw therefrom by written notice to
the Company, the managing underwriter and the Initiating Holders. The
Registrable Securities and/or other securities so withdrawn shall also be
withdrawn from registration.

          3.2 Company Registration.

               (a) Notice of Registration. If at any time or from time to time
the Company shall determine to register any of its securities, either for its
own account or the account of a security holder or holders, other than (i) a
registration relating solely to employee benefit plans, (ii) a registration
relating solely to a Commission Rule 145 transaction, or (iii) a registration
pursuant to Section 3.1 hereof, the Company will:

                    (i) promptly give to each Holder written notice thereof; and

                    (ii) use its best efforts to include in such registration
(and any related qualification under blue sky laws or other compliance), and in
any underwriting involved therein, all the Registrable Securities specified in a
written request or requests, made within twenty (20) days after receipt of such
written notice from the Company, by any Holder, subject to Section 3.2(b)
hereof.

               (b) Underwriting. If the registration of which the Company gives
notice is for a registered public offering involving an underwriting, the
Company shall so advise the Holders as a part of the written notice given
pursuant to Section 3.2(a)(i). In such event the right of any Holder to
registration pursuant to Section 3.2 shall be conditioned upon such Holder's
participation in such underwriting and the inclusion of Registrable Securities
in the underwriting to the extent provided herein. All Holders proposing to
distribute their securities through such underwriting shall (together with the
Company) enter into an underwriting agreement in customary form with the
managing underwriter selected for such underwriting by the Company.
Notwithstanding any other provision of this Section 3.2, if the managing
underwriter determines that marketing factors require a limitation of the number
of shares to be underwritten, the managing underwriter may limit the Registrable
Securities and other securities to be distributed through such underwriting, but
in no event shall the number of Registrable Securities to be included in such
offering be less than twenty percent (20%) of the total number of securities to
be included in such offering, unless such offering is the initial public
offering of the Company's Common Stock and such registration does not include
shares of any other selling shareholders, in which event any or all of the
Registrable Securities of the Holders may be excluded from such offering. The
Company shall so advise all Holders distributing their securities through such
underwriting of such limitation, and the number of shares of Registrable

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Securities that may be included in the registration and underwriting shall be
allocated among all Holders in proportion, as nearly as practicable, to the
respective amounts of Registrable Securities held by such Holders at the time of
filing the registration statement or in such other manner as shall be agreed to
by the Company and Holders of a majority of the Registrable Securities proposed
to be included in such registration. To facilitate the allocation of shares in
accordance with the above provisions, the Company may round the number of shares
allocated to any Holder or holder to the nearest one hundred (100) shares. If
any Holder or holder disapproves of the terms of any such underwriting, such
Holder or holder may elect to withdraw therefrom by written notice to the
Company and the managing underwriter. Any securities excluded or withdrawn from
such underwriting shall be withdrawn from such registration.

               (c) Right to Terminate Registration. The Company shall have the
right to terminate or withdraw any registration initiated by it under this
Section 3.2 prior to the effectiveness of such registration whether or not any
Holder has elected to include securities in such registration. The Registration
Expenses of such withdrawn registration shall be borne by the Company in
accordance with Section 3.4 hereof.

          3.3 Registration on Form S-3.

               (a) If any Holder or Holders of in excess of twenty percent (20%)
of the Registrable Securities or twenty percent (20%) of the Registrable
Securities held by the Investors who purchased Registrable Securities pursuant
to the Series C Stock Purchase Agreement dated June 7, 2000 by and among the
Company and those Investors listed on Exhibit A thereto (the "Series C
Agreement"), the Series D Stock Purchase Agreement dated April 10, 2003 by and
among the Company and those Investors listed on Exhibit A thereto (the "Series D
Agreement") and/or the Series E Agreement request that the Company file a
registration statement on Form S-3 (or any successor form to Form S-3), or any
similar short-term registration statement, for a public offering of Registrable
Securities, the reasonably anticipated aggregate price to the public of which,
net of underwriting discounts and commissions, would exceed $1,000,000 and the
Company is a registrant entitled to use Form S-3 to register the Registrable
Securities for such an offering, the Company shall use its best efforts to cause
such Registrable Securities to be registered on such form for the offering as
soon as practicable after receipt of the request or requests of the Holders and
to cause such Registrable Securities to be qualified in such jurisdictions as
the Holder or Holders may reasonably request; provided, however, that the
Company shall not be required to effect more than five (5) registrations
pursuant to this Section 3.3 or more than two (2) such registrations in any
twelve (12) month period. After the Company's first public offering of its
securities, the Company will use its best efforts to qualify for Form S-3
registration or a similar short-form registration. The provisions of Section
3.1(b) shall be applicable to each registration initiated under this Section
3.3.

               (b) Notwithstanding the foregoing, the Company shall not be
obligated to take any action pursuant to this Section 3.3: (i) in any particular
jurisdiction in which the Company would be required to execute a general consent
to service of process in effecting such registration, qualification or
compliance unless the Company is already subject to service in such jurisdiction
and except as may be required by the Securities Act; (ii) during the period
starting with the date sixty (60) days prior to the Company's estimated date of
filing of, and ending on the date three (3) months immediately following, the
effective date of any registration statement pertaining to securities of the

<PAGE>

Company (other than a registration of securities in a Rule 145 transaction or
with respect to an employee benefit plan), provided that the Company is actively
employing in good faith reasonable efforts to cause such registration statement
to become effective; or (iii) if the Company shall furnish to such Holder a
certificate signed by the President of the Company stating that in the good
faith judgment of the Board of Directors it would be seriously detrimental to
the Company or its shareholders for registration statements to be filed in the
near future, then the Company's obligation to use its best efforts to file a
registration statement shall be deferred for a period not to exceed ninety (90)
days from the receipt of the request to file such registration by such Holder;
provided, however, that the Company shall not exercise such right more than once
in any twelve-month period.

               3.4 Expenses of Registration. All Registration Expenses incurred
in connection with registrations pursuant to Sections 3.1 and 3.2 shall be borne
by the Company. All Registration Expenses incurred in connection with
registrations pursuant to Section 3.3 shall be borne by the holders of
securities included in such registration pro rata on the basis of the number of
shares so registered. All Selling Expenses relating to securities registered
pursuant to Sections 3.1, 3.2 and 3.3 shall be borne by the holders of
securities included in such registration pro rata on the basis of the number of
shares so registered; provided, however, the Company shall pay the reasonable
fees and expenses of one special counsel to the Holders in connection with
registrations pursuant to Sections 3.1, 3.2 and 3.3.

               3.5 Registration Procedures. In the case of each registration,
qualification or compliance effected by the Company pursuant to this Section 3,
the Company will keep each Holder advised in writing as to the initiation of
each registration, qualification and compliance and as to the completion
thereof. The Company will use its best efforts to:

                    (a) Prepare and file with the Commission a registration
statement with respect to such securities and, with respect to registrations
pursuant to Section 3.3, use its best efforts to cause such registration
statement to become and remain effective until the earlier to occur of (i) one
hundred twenty (120) days (which one hundred twenty (120) day period shall not
include any days during which the Holders shall be prohibited from selling any
Registrable Securities for the reasons described in Section 3.5(h) or 3.5(i),
(iii) and (iv)) or (ii) the distribution described in the Registration Statement
has been completed;

                    (b) Prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectus used in connection
with such registration statement as may be necessary to comply with the
provisions of the Securities Act with respect to the disposition of all
securities covered by such registration statement;

                    (c) Furnish to the Holders participating in such
registration and to the underwriters of the securities being registered, if any,
such reasonable number of copies of the registration statement, preliminary
prospectus, final prospectus and such other documents they may reasonably
request in order to facilitate the disposition of Registrable Securities by
them;

                    (d) register and qualify the securities covered by such
registration statement under such other securities or Blue Sky laws of such
jurisdictions as shall be reasonably requested by the Holders, provided that the
Company shall not be required in connection therewith or as a condition thereto
to qualify to do business or to file a general consent to service of process in
any such states or jurisdictions;

<PAGE>

                    (e) in the event of any underwritten public offering, enter
into and perform its obligations under an underwriting agreement, in usual and
customary form, with the managing underwriter of such offering;

                    (f) cause all such Registrable Securities registered
pursuant hereunder to be listed on each securities exchange on which similar
securities issued by the Company are then listed;

                    (g) provide a transfer agent and registrar for all
Registrable Securities registered pursuant hereunder and a CUSIP number for all
such Registrable Securities, in each case not later than the effective date of
such registration;

                    (h) As soon as practicable notify the Holders at any time
when a prospectus relating to the registration statement covering the
Registrable Securities is required to be delivered under the Securities Act or
the happening of any event as a result of which the prospectus included in such
registration statement, as then in effect, includes an untrue statement of a
material fact or omits to state a material fact required to be stated therein or
necessary to make the statements therein not misleading in the light of the
circumstances then existing and the Company shall promptly prepare and furnish
to the Holders a reasonable number of copies of a supplement or amendment to
such prospectus as may be necessary so that, as thereafter delivered to the
purchasers of such securities, such prospectus shall not contain an untrue
statement of a material fact or omit to state any material fact required to be
stated therein or necessary to make the statements therein in the light of
circumstances under which were made, not misleading;

                    (i) Promptly notify the Holders and each underwriter, if
any:

                         (i) when such registration statement or any prospectus
used in connection therewith has been filed and, with respect to such
registration statement or any post-effective amendment thereto, when the same
has become effective;

                         (ii) of any written comments from the Commission with
respect to any filing referred to in clause (i) and of any written request by
the Commission for amendments or supplements to such registration statement or
prospectus;

                         (iii) of the notification to the Company by the
Commission or any other regulatory authority of its initiation of any proceeding
with respect to, or of the issuance by the Commission or any other regulatory
authority of, any stop order suspending the effectiveness of such registration
statement; and

                         (iv) of the receipt by the Company of any notice with
respect to the suspension of the qualification of any Registrable Shares for
sale under applicable securities or blue sky laws of any jurisdiction;

<PAGE>

and, in the case of clauses (ii), (iii) and (iv), promptly use all reasonable
and diligent efforts (A) to respond satisfactorily to any such comments and to
file promptly any necessary amendments or supplements, (B) to prevent the
issuance of any stop order to obtain its withdrawal if such stop order should be
issued and (C) to obtain the withdrawal of any such suspension or qualification,
respectively; and

                    (j) furnish to the Holders a signed counterpart, addressed
to the Holder (and each underwriter, if any) of:

                         (i) an opinion of counsel to the Company, dated the
effective date of such registration statement (and, if such registration
includes an underwritten public offering, dated the date of the closing under
the underwriting agreement), reasonably satisfactory in form and substance to
the underwriter or underwriter's counsel; and

                         (ii) a "comfort" letter (in the case of an underwritten
public offering), dated the effective date of such registration statement and
dated the date of the closing under the underwriting agreement, signed by the
independent public accountants who have certified the Company's financial
statement included in such registration statement, provided that the Holders
provide such accountants with such certificates as are reasonably and
customarily requested by such accountants;

in each case covering substantially the same matters with respect to such
registration statement (and the prospectus included therein) and, in the case of
the accountants' letter, with respect to events subsequent to the date of such
financial statements and other financial matters, as are customarily covered in
opinions of issuer's counsel and in accountants' letters delivered to the
underwriters in underwritten public offerings of securities.

               3.6 Indemnification.

                    (a) The Company will indemnify each Holder, each of its
officers, directors, partners and legal counsel, and each person controlling
such Holder within the meaning of Section 15 of the Securities Act, with respect
to which registration, qualification or compliance has been effected pursuant to
this Section 3, and each underwriter, if any, and each person who controls any
underwriter within the meaning of Section 15 of the Securities Act, against all
expenses, claims, losses, damages or liabilities (or actions in respect
thereof), including any of the foregoing incurred in settlement of any
litigation, commenced or threatened, arising out of or based on any untrue
statement (or alleged untrue statement) of a material fact contained in any
registration statement, prospectus, offering circular or other document, or any
amendment or supplement thereto, incident to any such registration,
qualification or compliance, or based on any omission (or alleged omission) to
state therein a material fact required to be stated therein or necessary to make
the statements therein, in light of the circumstances in which they were made,
not misleading, or any violation by the Company of the Securities Act or any
rule or regulation promulgated under the Securities Act applicable to the
Company in connection with any such registration, qualification or compliance,
and the Company will reimburse each such Holder, each of its officers,
directors, partners, and legal counsel and each person controlling such Holder,
each such underwriter and each person who controls any such underwriter, for any
legal and any other expenses reasonably incurred in

<PAGE>

connection with investigating, preparing or defending any such claim, loss,
damage, liability or action, provided that the Company will not be liable in any
such case to the extent that any such claim, loss, damage, liability or expense
arises out of or is based on any untrue statement or omission or alleged untrue
statement or omission, made in reliance upon and in conformity with written
information furnished to the Company by such Holder, controlling person or
underwriter and stated to be specifically for use therein.

                    (b) Each Holder will, if Registrable Securities held by such
Holder are included in the securities as to which such registration,
qualification or compliance is being effected, indemnify the Company, each of
its directors, officers, and legal counsel, each underwriter, if any, of the
Company's securities covered by such a registration statement, each person who
controls the Company or such underwriter within the meaning of Section 15 of the
Securities Act, and each other Holder, each of its officers, directors, partners
and legal counsel and each person controlling such Holder within the meaning of
Section 15 of the Securities Act, against all claims, losses, damages and
liabilities (or actions in respect thereof) arising out of or based on any
untrue statement (or alleged untrue statement) of a material fact contained in
any such registration statement, prospectus, offering circular or other
document, or any omission (or alleged omission) to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and will reimburse the Company, such Holders, such directors,
officers, persons, underwriters or control persons for any legal or any other
expenses reasonably incurred in connection with investigating or defending any
such claim, loss, damage, liability or action, in each case to the extent, but
only to the extent, that such untrue statement (or alleged untrue statement) or
omission (or alleged omission) is made in such registration statement,
prospectus, offering circular or other document in reliance upon and in
conformity with written information furnished to the Company by such Holder and
stated to be specifically for use therein. Notwithstanding the foregoing, the
liability of each Holder under this subsection (b) shall be limited in an amount
equal to the net proceeds to each such Holder of Registrable Securities sold as
contemplated herein, unless such liability resulted from willful misconduct or
gross negligence by such Holder.

                    (c) Each party entitled to indemnification under this
Section 3.6 (the "Indemnified Party") shall give notice to the party required to
provide indemnification (the "Indemnifying Party") promptly after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought, and shall permit the Indemnifying Party to assume the defense of any
such claim or any litigation resulting therefrom, provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not
unreasonably be withheld), and the Indemnified Party may participate in such
defense at such party's expense, and provided further that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations under this Section 3 unless the failure to
give such notice is materially prejudicial to an Indemnifying Party's ability to
defend such action and provided further, that the Indemnifying Party shall not
assume the defense for matters as to which there is a conflict of interest or
separate and different defenses but shall bear the expense of such defense
nevertheless. No Indemnifying Party, in the defense of any such claim or
litigation, shall, except with the consent of each Indemnified Party, consent to
entry of any judgment or enter into any settlement which does not include as an
unconditional term thereof the giving by the claimant or plaintiff to such
Indemnified Party of a release from all liability in respect to such claim or
litigation.

<PAGE>

                    (d) If the indemnification provided for in this Section 3.6
is held by a court of competent jurisdiction to be unavailable to an indemnified
party with respect to any loss, liability, claim, damage or expense referred to
herein, then the indemnifying party, in lieu of indemnifying such indemnified
party hereunder, shall contribute to the amount paid or payable by such
indemnified party as a result of such loss, liability, claim, damage or expense
in such proportion as is appropriate to reflect the relative fault of the
indemnifying party on the one hand and of the indemnified party on the other in
connection with the statements or omissions that resulted in such loss,
liability, claim, damage or expense, as well as any other relevant equitable
considerations. The relative fault of the indemnifying party and of the
indemnified party shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or the
omission to state a material fact relates to information supplied by the
indemnifying party or by the indemnified party and the parties' relative intent,
knowledge, access to information, and opportunity to correct or prevent such
statement or omission. Notwithstanding the foregoing, the liability of each
Holder under this subsection (d) shall be limited to an amount equal to the net
proceeds to each such Holder of Registrable Securities sold as contemplated
herein, unless such liability resulted from willful misconduct or gross
negligence by such Holder.

                    (e) Notwithstanding the foregoing, to the extent that the
provisions on indemnification and contribution contained in the underwriting
agreement entered into in connection with the underwritten public offering are
in conflict with the foregoing provisions, the provisions in the underwriting
agreement shall control.

                    (f) The obligations of the Company and Holders under this
Section 3.6 shall survive the completion of any offering of Registrable
Securities in a registration statement under this Section 3, and otherwise.

               3.7 Information by Holder. The Holder or Holders of Registrable
Securities included in any registration shall furnish to the Company such
information regarding such Holder or Holders, the Registrable Securities held by
them, and the distribution proposed by such Holder or Holders as the Company may
request in writing and as shall be required in connection with any registration,
qualification or compliance referred to in this Section 3.

               3.8 Rule 144 Reporting. With a view to making available the
benefits of certain rules and regulations of the Commission which may at any
time permit the sale of the Restricted Securities to the public without
registration, after such time as a public market exists for the Common Stock of
the Company, the Company agrees to use its best efforts to:

                    (a) Make and keep public information available, as those
terms are understood and defined in Rule 144 under the Securities Act, at all
times after the effective date that the Company becomes subject to the reporting
requirements of the Securities Act or the Securities Exchange Act of 1934, as
amended;

                    (b) File with the Commission in a timely manner all reports
and other documents required of the Company under the Securities Act and the
Securities Exchange Act of 1934, as amended (at any time after it has become
subject to such reporting requirements); and

<PAGE>

                    (c) So long as a Holder owns any Restricted Securities to
furnish to the Holder forthwith upon request a written statement by the Company
as to its compliance with the reporting requirements of said Rule 144 (at any
time after 90 days after the effective date of the first registration statement
filed by the Company for an offering of its securities to the general public),
and of the Securities Act and the Securities Exchange Act of 1934 (at any time
after it has become subject to such reporting requirements), a copy of the most
recent annual or quarterly report of the Company, and such other reports and
documents of the Company and other information in the possession of or
reasonably obtainable by the Company as a Holder may reasonably request in
availing itself of any rule or regulation of the Commission allowing a Holder to
sell any such securities without registration.

               3.9 Transfer of Registration Rights. The rights to cause the
Company to register securities granted Holders under Sections 3.1, 3.2 and 3.3
may be assigned to a transferee or assignee who acquires at least 300,000 Shares
or Registrable Securities, or to any transferee or assignee who is a subsidiary,
parent organization, partner, limited partner, retired partner, family member or
trust of a Holder or the estate of such person or entity, provided that such
transfer may otherwise be effected in accordance with applicable securities
laws.

               3.10 Standoff Agreement. Each Holder agrees, upon request of the
Company or the underwriters managing any underwritten offering of the Company's
securities, not to sell, make any short sale of, loan, grant any option for the
purchase of, or otherwise transfer or dispose of any Registrable Securities
(other than those included in the registration) without the prior written
consent of the Company or such underwriters, as the case may be, for a period of
time not to exceed 180 days from the effective date of such registration,
provided that:

                    (a) such agreement shall only apply to the initial public
offering of the Company; and

                    (b) all officers, directors, other holders of rights to
cause the Company to register securities and holders of more than one percent of
the Company's outstanding voting stock have entered into similar agreements;
provided, however, that, notwithstanding the foregoing, in the event that the
underwriters in any public offering of the Company's securities release any
persons named in subsection (b) from their obligations under the agreements
referenced in subsection (b) with respect to any offering, then the Company
shall promptly notify the Holders and the Holders shall be deemed released from
their obligations under this Section 3.10 with respect to such offering;
provided, further, that, in the event that the underwriters release any persons
named in subsection (b) from their obligations under the agreements referenced
in subsection (b) with respect to less than all of their Company securities,
then the Holders shall be deemed released from their obligations under this
Section 3.10 with respect to the same percentage of their Registrable Securities
as the percentage of the Company's securities released with respect to such
other persons. The Company hereby agrees that it shall use its best efforts to
include the foregoing proviso in any underwriting agreement entered into during
the term hereof.

               3.11 Termination of Registration Rights. The rights granted under
this Section 3 shall terminate on the earlier of (i) the fifth anniversary of
the closing of the initial underwritten public offering of the Company's
securities pursuant to a registration statement filed under the

<PAGE>

Securities Act or (ii) on such date as all Registrable Securities may be sold
under Rule 144 during any 90-day period (without regard to the volume
limitations thereunder and without regard to Rule 144(k)). The rights granted
under this Section 3 shall not terminate with respect to any Holder pursuant to
subsection (ii) above for so long as such Holder owns more than one percent (1%)
of the Company's outstanding stock.

     4. Right of First Offer.

          4.1 Right of First Offer Upon Issuances of Securities by the Company.

               (a) The Company hereby grants, on the terms set forth in this
Section 4.1, to each Investor who holds at least 300,000 Shares or Registrable
Securities (as adjusted for stock splits, stock dividends, recapitalizations and
the like) purchased pursuant to the Series B Stock Purchase Agreement dated
October 12, 1998 by and among the Company and those Investors listed on Exhibit
A thereto (the "Series B Agreement"), the Series C Agreement, the Series D
Agreement and/or the Series E Agreement (a "Major Investor"), the right of first
offer to purchase all or any part of such Major Investor's pro rata share of the
New Securities (as defined in Section 4.1(b)) which the Company may, from time
to time, propose to sell and issue. The Major Investors may purchase said New
Securities on the same terms and at the same price at which the Company proposes
to sell the New Securities. The pro rata share of each Major Investor, for
purposes of this right of first offer, is (except as set forth in paragraph
4.1(e) below) the ratio of the total number of shares of Common Stock held by
such Major Investor, including any shares of Common Stock into which shares of
Preferred Stock held by such Major Investor are convertible, to the total number
of shares of Common Stock outstanding immediately prior to the issuance of the
New Securities (including any shares of Common Stock into which outstanding
shares of Preferred Stock are convertible).

               (b) "New Securities" shall mean any capital stock of the Company,
whether now authorized or not, and any rights, options or warrants to purchase
said capital stock, and securities of any type whatsoever that are, or may
become, convertible into said capital stock; provided that "New Securities" does
not include (i) the Shares purchased under the Series E Agreement or the
Registrable Securities, (ii) securities offered pursuant to a registration
statement filed under the Securities Act, (iii) securities issued pursuant to
the acquisition of another corporation by the Company by merger, purchase of
substantially all of the assets, or other reorganization, as approved by the
Company's Board of Directors, (iv) all shares of Common Stock or other
securities hereafter issued or issuable to officers, directors, employees,
scientific advisors or consultants of the Company pursuant to any employee or
consultant stock offering, plan or arrangement approved by the Board of
Directors of the Company, (v) all shares of Common Stock or other securities
hereafter issued in connection with or as consideration for acquisition or
licensing of technology, as approved by the Company's Board of Directors, and
(vi) all shares of Common Stock or other securities issued in connection with
equipment leasing or equipment financing arrangements approved by the Board of
Directors of the Company.

               (c) In the event the Company proposes to undertake an issuance of
New Securities, it shall give to the Major Investors written notice (the
"Notice") of its intention, describing the type of New Securities, the price,
the terms upon which the Company proposes to issue the same, and a statement as
to the number of days from receipt of such Notice within which

<PAGE>

the Major Investors must respond to such Notice. The Major Investors shall have
thirty (30) days from the date of receipt of the Notice to purchase any or all
of the New Securities for the price and upon the terms specified in the Notice
by giving written notice to the Company and stating therein the quantity of New
Securities to be purchased and forwarding payment for such New Securities to the
Company if immediate payment is required by such terms.

               (d) In the event the Major Investors fail to exercise in full the
right of first offer within said thirty (30) day period, the Company shall have
ninety (90) days thereafter to sell or enter into an agreement (pursuant to
which the sale of New Securities covered thereby shall be closed, if at all,
within thirty (30) days from date of said agreement) to sell the New Securities
respecting which the Major Investor rights were not exercised, at a price and
upon general terms no more favorable to the Major Investors thereof than
specified in the Notice. In the event the Company has not sold the New
Securities within said ninety (90) day period (or sold and issued New Securities
in accordance with the foregoing within thirty (30) days from the date of said
agreement), the Company shall not thereafter issue or sell any New Securities
without first offering such securities to the Major Investors in the manner
provided above.

               (e) The right of first offer granted under this Section 4.1 shall
expire upon:

                    (i) The date upon which a registration statement filed by
the Company under the Securities Act (other than a registration of securities in
a Rule 145 transaction or with respect to an employee benefit plan) in
connection with an underwritten public offering of its securities first becomes
effective and the securities registered thereunder are sold.

                    (ii) For each Major Investor, the date on which such Major
Investor no longer holds a minimum of 300,000 Shares or Registrable Securities
(as adjusted for stock splits, stock dividends, recapitalizations and the like)
originally purchased pursuant to the Series B Agreement, the Series C Agreement,
the Series D Agreement and/or the Series E Agreement.

                    (iii) The tenth anniversary of the date of this Agreement.

               (f) The right of first offer granted under this Section 4.1 is
assignable by the Investors to any transferee of a minimum of 300,000 Shares or
Registrable Securities (as adjusted for stock splits, stock dividends,
recapitalizations and the like) originally purchased pursuant to the Series B
Agreement, the Series C Agreement, the Series D Agreement and/or the Series E
Agreement.

               (g) Each Investor who is a party to the Previous Investor Rights
Agreement hereby waives its right of first refusal under the Previous Investor
Rights Agreement, including any notice rights pertaining thereto, to purchase
the shares of Series E Preferred Stock being issued and sold pursuant to the
Series E Agreement.

     5. Covenants of the Company.

          5.1 Financial Information. The Company will provide each Investor the
following reports for so long as the Investor is a holder of at least 300,000
Shares or Registrable Securities (as adjusted for stock splits, stock dividends,
recapitalizations and the like), including for purposes of this Section 5 any
such Shares which have been transferred to a constituent partner of an Investor:

<PAGE>

               (a) As soon as practicable after the end of each fiscal year, and
in any event within 90 days thereafter, consolidated balance sheets of the
Company and its subsidiaries, if any, as of the end of such fiscal year, and
consolidated statements of income, stockholders' equity and cash flows of the
Company and its subsidiaries, if any, for such year, prepared in accordance with
generally accepted accounting principles and setting forth in each case in
comparative form the figures for the previous fiscal year, all in reasonable
detail and, if requested by the Investors, certified by independent public
accountants selected by the Company.

               (b) As soon as practicable after the end of each month and in any
event within 30 days thereafter, a consolidated balance sheet of the Company and
its subsidiaries, if any, as of the end of each such month, consolidated
statements of income, consolidated statements of changes in financial condition,
and a consolidated statement of cash flow of the Company and its subsidiaries
for such period and for the current fiscal year to date, and setting forth in
each case in comparative form the figures for corresponding periods in the
previous fiscal year, prepared in accordance with generally accepted accounting
principles (other than for accompanying notes), subject to changes resulting
from year-end audit adjustments, all in reasonable detail and signed by the
principal financial or accounting officer of the Company.

               (c) A copy of the annual budget for the next fiscal year of the
Company containing profit and loss projections, cash flow projections, and
capital expenditures, as soon as it is available but in any event within thirty
(30) days prior to the end of the current fiscal year.

               (d) The obligation of the Company to furnish financial
information under paragraphs (a), (b) and (c) of this Section 5.1 shall
terminate upon a public offering or when the Company becomes subject to the
reporting requirements of the Securities Exchange Act of 1934, as amended.

          5.2 Positive Covenants. The Company hereby agrees as follows:

               (a) The Company will promptly pay and discharge, or cause to be
paid and discharged, when due and payable, all lawful taxes, assessments, and
governmental charges or levies imposed upon the income, profits, property or
business of the Company or any subsidiary; provided, however, that any such tax,
assessment, charge or levy need not be paid if the validity thereof shall
currently be contested in good faith by appropriate proceedings and if the
Company shall have set aside on its books adequate reserves with respect
thereof, and provided further, that the Company will pay all such taxes,
assessments, charges, or levies forthwith upon the commencement of proceedings
to foreclose any lien that may have attached as security therefor. The Company
will promptly pay or cause to be paid when due, or in conformance with customary
trade terms, all other indebtedness incident to the operations of the Company;

               (b) The Company will keep its assets and those of its
subsidiaries that are of an insurable character insured by financially sound and
reputable insurers against loss or damage by fire, extended coverage, and
explosion insurance in amounts customary for companies in similar

<PAGE>

businesses similarly situated, and the Company will maintain, with financially
sound and reputable insurers, insurance against other hazards, risks and
liabilities to persons and property to the extent and in the manner customary
for companies in similar businesses similarly situated;

               (c) The Company and all its subsidiaries shall duly observe and
conform to all valid requirements of governmental authorities, and applicable
laws, relating to the conduct of their businesses or to their property or
assets;

               (d) The Company will cause each person now or hereafter employed
by it or any subsidiary with access to confidential information to enter into a
proprietary information and inventions agreement substantially in the form
approved by the Board of Directors;

               (e) The Company shall not enter into transactions with the
affiliates of the Company except on terms substantially as beneficial to the
Company as similar arrangements with the independent third parties; and the
Company shall notify each Investor holding at least 300,000 Shares (as adjusted
for stock splits, stock dividends, recapitalizations and the like) prior to
entering into any such transaction with an aggregate value in excess of
$100,000; and

               (f) The Company shall promptly notify each Investor holding at
least 300,000 Shares (as adjusted for stock splits, stock dividends,
recapitalizations and the like) of any material default under any material loan,
lease, contract or any other agreement with a third party.

          5.3 Observer Rights. Any Investor holding at least 1,000,000 shares of
Series C Preferred Stock, or in the case of Pequot Private Equity Fund II, L.P.
("Pequot"), 50% of the shares of Registrable Securities held by Pequot as of
June 7, 2000, or in the case of The Entrepreneurs' Fund, 615,000 shares of
Series D Preferred Stock, or in the case of Versant Ventures II, L.P.
("Versant"), 50% of the shares of Registrable Securities held by Versant as of
the date hereof, who does not have one of its partners or members, or a partner
or member of an affiliated entity, serving as a member of the Company's Board of
Directors shall be entitled to designate a representative to attend all meetings
of the Company's Board of Directors in a nonvoting observer capacity and, in
this respect, the Company shall give such representative copies of all notices,
minutes, consents and other materials that it provides to its directors at such
time as it provides such materials to its directors; provided, however, that
such representative shall agree to hold in confidence and trust and to act as a
fiduciary of the Company with respect to all information so provided; and,
provided further, that the Company reserves the right to withhold any
information and to exclude such representative from any meeting or portion
thereof if access to such information or attendance at such meeting could
adversely affect the attorney-client privilege between the Company and its
counsel. The Company agrees to reimburse all reasonable expenses incurred by
such representative directly associated with attending meetings of the Company's
Board of Directors.

          5.4 Confidentiality. Each Investor agrees that any information
obtained by such Investor pursuant to this Section 5 which is identified by the
Company as being proprietary to the Company or otherwise confidential will not
be disclosed without the prior written consent of the Company. Each Investor
further acknowledges and understands that any information so obtained which may
be considered "inside" non-public information will not be utilized by such
Investor in connection with purchases and/or sales of the Company's securities
except in compliance with applicable state and federal anti-fraud statutes.

<PAGE>

          5.5 Redemption. The Investors hereby acknowledge and agree that the
Company shall use part of the proceeds to the Company from the sale of Series E
Preferred Stock pursuant to the Series E Agreement to redeem 500,000 shares of
Series A Preferred Stock at a price per share of $5.25 from The Nice Trust.

          5.6 Termination of Covenants. The covenants of the Company set forth
in this Section 5 shall terminate in all respects on the earlier to occur of (i)
date of the closing of an initial firm commitment underwritten public offering
pursuant to an effective registration statement under the Securities Act,
covering the offer and sale of the Company's Common Stock and (ii) the tenth
anniversary of the date of this Agreement.

     6. General Provisions.

          6.1 Amendment and Waiver. Any term of this Agreement may be amended
and the observance of any term of this Agreement may be waived (either generally
or in a particular instance and either retroactively or prospectively), only
with the written consent of the Company and the holders of two-thirds (2/3) of
the shares of the Common Stock issued or issuable upon conversion of the Shares;
provided that in addition to the vote otherwise required by this Section 6.1,
Section 5.5 may not be amended without the written consent of a majority in
interest of the holders of Series A Preferred Stock of the Company. Any
amendment or waiver effected in accordance with this Section 6.1 shall be
binding upon all holders of any Shares or Registrable Securities at the time
outstanding, each future holder of all such securities and the Company.

          6.2 Governing Law. This Agreement shall be governed by and construed
under the internal laws of the State of California without regard to conflict of
laws provisions.

          6.3 Successors and Assigns. Except as otherwise expressly provided,
the provisions of this Agreement shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors, and administrators of the
parties.

          6.4 Severability. In case any provision of this Agreement becomes or
is declared by a court of competent jurisdiction to be unenforceable, this
Agreement shall continue in full force and effect without said provision;
provided, however, that no such severability shall be effective if it materially
changes the economic benefit of this Agreement to any party.

          6.5 Notices. All notices and other communications required or
permitted hereunder shall be in writing and shall be deemed effectively given
upon personal delivery or upon deposit with the United States Post Office, by
first class mail, postage prepaid, addressed: (a) if to the Investors, at the
Investor address as set forth on Attachment A hereto, or at such other address
as the Investors shall have furnished to the Company in writing, or (b) if to
the Company, at its current address or at such other address as the Company
shall have furnished to the Investors in writing.

          6.6 Counterparts. This Agreement may be executed in any number of
counterparts, each of which is an original, and all of which together shall
constitute one instrument. This Agreement shall become effective when
counterparts have been signed by each of the parties and delivered by facsimile
or other means to the other parties.

<PAGE>

          6.7 Titles and Subtitles. The titles and subtitles used in this
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

          6.8 Expenses. If any action at law or in equity is necessary to
enforce or interpret the terms of this Agreement, the prevailing party shall be
entitled to reasonable attorneys' fees, costs and necessary disbursements in
addition to any other relief to which such party may be entitled.

          6.9 Aggregation of Stock. All shares of Registrable Securities held or
acquired by affiliated entities or persons shall be aggregated together for the
purpose of determining the availability of any rights under this Agreement.

          6.10 Entire Agreement. This Agreement (including the schedules and
exhibits hereto) amends and restates in its entirety the Previous Investor
Rights Agreement and constitutes the full and entire understanding and agreement
between the parties with regard to the subject hereof.

          6.11 Aggregation. All Shares held or acquired by affiliated persons,
funds and entities and constituent partners and members will be aggregated for
the purpose of determining the availability of any rights under this Agreement.

                [Remainder of this page intentionally left blank]
<PAGE>

IN WITNESS WHEREOF, this Investor Rights Agreement has been executed as of the
date first above written.

                                        EYEONICS, INC.

                                        a Delaware corporation


                                        By: /s/ J. Andy Corley
                                            ------------------------------------
                                            J. Andy Corley, President

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        VERSANT VENTURE CAPITAL II, L.P.
                                        VERSANT SIDE FUND II, L.P.
                                        VERSANT AFFILIATES FUND II-A, L.P.

                                        By: Versant Ventures II, L.L.C.,
                                            Its General Partner


                                        By: /s/ Charles M. Warden
                                            ------------------------------------
                                            Charles M. Warden, Managing Director

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        ADAM VENTURES, L.P.
                                        a Delaware limited partnership

                                        By: Adam Ventures Management, L.L.C.


                                        By: /s/ J. Casey McGlynn
                                            ------------------------------------
                                            J. Casey McGlynn
                                        Title: Authorized Signatory

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        BRENTWOOD AFFILIATES FUND II, L.P.

                                        By: Brentwood VIII Ventures, LLC,
                                            its General Partner


                                        By: /s/ illegible
                                            ------------------------------------
                                            ___________________, Managing Member


                                        BRENTWOOD ASSOCIATES VIII, L.P.

                                        By: Brentwood VIII Ventures, LLC,
                                            its General Partner


                                        By: /s/ illegible
                                            ------------------------------------
                                            Managing Member

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        BRUCE FEUCHTER


                                        /s/ Bruce Feuchter
                                        ----------------------------------------


                                        SYCR INVESTMENT FUND I, LLC


                                        By: /s/ illegible
                                            ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------


                                        STRADLING YOCCA CARLSON & RAUTH
                                        INVESTMENT PARTNERSHIP OF 1982


                                        By: /s/ Bruce Feuchter
                                            ------------------------------------
                                            Bruce Feuchter, General Partner

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        J. CASEY MCGLYNN


                                        /s/ J. Casey McGlynn
                                        ----------------------------------------


                                        CALNATIONAL BANK CUST FBO
                                        J. CASEY MCGLYNN


                                        By: /s/ J. Casey McGlynn
                                            ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        ABS VENTURES VI L.L.C.
                                        By ABS Ventures VI L.P., its sole member
                                        By Calvert Capital IV L.L.C., its
                                        general partner


                                        By: /s/ Bruns H. Grayson
                                            ------------------------------------
                                            Bruns H. Grayson
                                            Senior Manager


                                        ABS INVESTORS L.L.C.


                                        By: /s/ James. M. Shapiro
                                            ------------------------------------
                                            James M. Shapiro, its Manager

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        PEQUOT PRIVATE EQUITY FUND II, L.P.

                                        By: Pequot Capital Management, Inc., its
                                            as Investment Manager


                                        By: /s/ Aryeh Davis
                                            ------------------------------------
                                        Name: Aryeh Davis
                                        Title: COO & General Counsel

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        JON OSGOOD


                                        /s/ Jon Osgood
                                        ----------------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        PETER N. RIEKES


                                        /s/ Peter N. Riekes
                                        ----------------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        THE WATKINS FAMILY TRUST


                                        By: /s/ Jay Watkins
                                            ------------------------------------
                                            Jay Watkins, Trustee

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        LARRY HAIMOVITCH 2000 SEPARATE PROPERTY
                                        REVOCABLE TRUST DATED MAY 9, 2000


                                        By: /s/ illegible
                                            ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        THE GEX FAMILY TRUST U/D/T DATED JUNE
                                        26, 1992


                                        By: /s/ Steven L. Gex
                                            ------------------------------------
                                            Steven L. Gex, Trustee

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        THE ENTREPRENEURS' FUND II, L.P.

                                        By: BW Management II, LLC,
                                            its General Partner


                                        By: /s/ C. Woodrow Rea
                                            ------------------------------------
                                            C. Woodrow Rea, Jr., Managing
                                            Director


                                        THE ENTREPRENEURS' GROWTH FUND, L.P.

                                        By: BW Management II, LLC,
                                            its General Partner


                                        By: /s/ C. Woodrow Rea
                                            ------------------------------------
                                            C. Woodrow Rea, Jr., Managing
                                            Director

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        RBW INVESTMENTS, LLC


                                        By: /s/ C. Woodrow Rea
                                            ------------------------------------
                                            C. Woodrow Rea, Jr., Managing
                                            Director

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        JOSEPH F. BRILANDO


                                        /s/ Joseph F. Brilando
                                        ----------------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        WS INVESTMENTS


                                        By: /s/ J. Casey McGlynn
                                            ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------


                                        WS INVESTMENT COMPANY, LLC
                                        (2003 A)


                                        By: /s/ J. Casey McGlynn
                                            ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------


                                        WS INVESTMENT COMPANY, LLC
                                        (2003 C)


                                        By: /s/ J. Casey McGlynn
                                            ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        JAMES GERIAK


                                        /s/ James Geriak
                                        ----------------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                        INVESTORS:

                                        ORRICK INVESTMENTS 2003 LLC


                                        By: /s/ illegible
                                            ------------------------------------
                                        Name:
                                              ----------------------------------
                                        Title:
                                               ---------------------------------

EYEONICS, INC.
SERIES E AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
<PAGE>

                                   SCHEDULE A

                              SCHEDULE OF INVESTORS

ABS INVESTORS, L.L.C.
890 Winter Street, Suite 225
Waltham, MA 02451

ABS VENTURES VI L.L.C.
890 Winter Street, Suite 225
Waltham, MA 02451

ADAM VENTURES, L.P.
c/o J. Casey McGlynn, Esq.
650 Page Mill Road
Palo Alto, CA 94304

BRENTWOOD ASSOCIATES VIII, L.P.
BRENTWOOD AFFILIATES FUND II, L.P.
450 Newport Center Drive, Suite 380
Newport Beach, California 92660

BRUCE FEUCHTER
660 Newport Center Drive
Suite 1600
Newport Beach, CA 92660

CALIFORNIA FEDERAL BANK IRA
FBO J. Casey McGlynn
650 Page Mill Road
Palo Alto, CA 94304

JAMES GERIAK
Orrick, Herrington & Sutcliffe LLP
4 Park Plaza, Suite 1600
Irvine, CA 92614-2558

J. CASEY MCGLYNN
650 Page Mill Road
Palo Alto, CA 94304

<PAGE>

JON OSGOOD
229 Marlborough Street
Boston, MA

JOSEPH F. BRILANDO
2637 Marine Way, Suite 100
Mountain View, CA 94043

LARRY HAIMOVITCH 2000 SEPARATE PROPERTY
REVOCABLE TRUST DATED MAY 9, 2000
4 Maritime Plaza
San Francisco, CA 94111

ORRICK INVESTMENTS 2003 LLC
Peter Lillevand
Old Federal Reserve Bank Building
400 Sansome Street
San Francisco, CA 94111-3143

PEQUOT PRIVATE EQUITY FUND II, L.P.
c/o Pequot Capital Management, Inc.
500 Nyala Farm Road
Westport, CT 06880

PETER N. REIKES
SG Cowen Securities Corp
1221 Avenue of the Stars
New York, NY 10020

RBW INVESTMENTS, LLC
c/o Shirley R. Elfar
800 W. El Camino Real, Suite 180
Mountain View, CA 94040

STRADLING YOCCA CARLSON & RAUTH
INVESTMENT PARTNERSHIP OF 1982
660 Newport Center Drive, Suite 1600
Newport Beach, California 92660

SYCR INVESTMENT FUND I, LLC
c/o Bruce Feuchter, Esq.
660 Newport Center Drive
Suite 1600
Newport Beach, CA 92660

THE ENTREPRENEURS' FUND II, L.P.
THE ENTREPRENEURS' GROWTH FUND, L.P.

<PAGE>

c/o Shirley R. Elfar
800 W. El Camino Real, Suite 180
Mountain View, CA 94040

THE GEX FAMILY TRUST U/D/T
DATED JUNE 26, 1992
9 New Haven
Laguna Nigel, CA 92677

THE WATKINS FAMILY TRUST
Jay Watkins
140 Solana Rd.
Portola Valley, CA 94028

VERSANT VENTURE CAPITAL II, L.P.
VERSANT SIDE FUND II, L.P.,
VERSANT AFFILIATES FUND II-A, L.P.
450 Newport Center Drive, Suite 600
Newport Beach, CA 92660
Attn: Charles M. Warden

WS INVESTMENTS
WS INVESTMENT COMPANY, LLC (2003 A)
WS INVESTMENT COMPANY, LLC (2003 C)
650 Page Mill Road
Palo Alto, CA 94304