<PAGE>   1


                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


   
                                  FORM 10-Q/A
                                AMENDMENT NO. 1
    

[X] Quarterly report pursuant to Section 13 or 15(d) of the Securities Exchange
    Act of 1934.

For the quarter period ended September 30, 1997

                                       OR
[ ] Transition report pursuant to Section 13 or 15(d) of the Securities Exchange
    Act of 1934.

For the transition period from ______ to ______



                         Commission File Number: 0-10640


                              COLLAGEN CORPORATION

             (Exact name of registrant as specified in its charter)


        Delaware                                         94-2300486
----------------------                        ----------------------------------
State of Incorporation                        I.R.S. Employer Identification No.

                  2500 Faber Place, Palo Alto, California 94303
                            Telephone: (415) 856-0200


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.

                                Yes  [X]     No  [ ]
                                   
Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the latest practicable date.

As of October 31, 1997, Registrant had outstanding 8,898,364 shares of common
stock, exclusive of 1,947,900 shares held by the Registrant as treasury stock.



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The undersigned registrant hereby amends Item 1. Financial Statements of Part I
of its Quarterly Report on Form 10-Q for the quarter ended September 30, 1997
as set forth below in order to correct a mathematical error on the registrant's
Consolidated Balance Sheets.
    



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                              COLLAGEN CORPORATION
                           CONSOLIDATED BALANCE SHEETS
                                   (Unaudited)
               (In thousands, except share and per share amounts)

   
<TABLE>
<CAPTION>
                                                                 September 30,            June 30,  
                                                                    1997                   1997 *
                                                                 -------------          ------------
<S>                                                               <C>                   <C>         
ASSETS
   Current assets:
     Cash and cash equivalents                                    $     16,162          $     18,481
     Short-term investments                                              7,792                 5,117
     Accounts receivable, net                                           12,701                10,759
     Inventories, net                                                   13,610                14,293
     Other current assets, net                                           9,957                 9,314
                                                                  ------------         -------------
           Total current assets                                         60,222                57,964

   Property and equipment, net                                          15,670                15,260
   Intangible assets and goodwill, net                                  13,979                14,764
   Investment in Boston Scientific Corporation                          70,522                83,874
   Other investments and assets, net                                    17,309                13,049
                                                                  ------------         -------------
                                                                  $    177,702         $     184,911
                                                                  ============         =============

LIABILITIES AND STOCKHOLDERS' EQUITY
   Current liabilities:
     Accounts payable                                             $      1,620          $      2,638
     Other accrued liabilities                                          12,828                13,638
     Income taxes payable                                               10,084                 9,376
     Notes payable                                                       2,030                    70
                                                                  ------------         -------------
           Total current liabilities                                    26,562                25,722

   Long-term liabilities:
     Deferred income taxes                                              32,245                35,448
     Other long-term liabilities                                         1,800                 3,795
                                                                  ------------         -------------
           Total long-term liabilities                                  34,045                39,243

   Commitments and contingencies
   Minority Interest                                                        19                    49

   Stockholders' equity:

     Preferred Stock, $.01 par value, authorized: 
        5,000,000 shares; none issued and outstanding                       --                    --
     Common stock, $.01 par value, authorized: 
        28,950,000 shares, issued: 10,770,304 shares 
        at September 30, 1997 (10,756,935 shares at 
        June 30, 1997), outstanding: 8,822,404 shares at
        September  30, 1997 (8,809,035 shares at June 30, 1997             108                   108
     Additional paid-in capital                                         67,297                67,204
     Retained earnings                                                  50,009                47,999
     Cumulative translation adjustment                                  (2,002)               (1,717)
     Unrealized gain on available-for-sale investments                  42,430                47,069
     Treasury stock, at cost, 1,947,900 shares at 
        September 30, 1997 and June 30, 1997                           (40,766)              (40,766)
                                                                  ------------         -------------
           Total stockholders' equity                                  117,076               119,897
                                                                  ------------         -------------
                                                                  $    177,702         $     184,911
                                                                  ============         =============
</TABLE>
    
* Amounts derived from audited financial statements at the date indicated.



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                              COLLAGEN CORPORATION
                        CONSOLIDATED STATEMENTS OF INCOME
                                   (Unaudited)
                    (In thousands, except per share amounts)

<TABLE>
<CAPTION>
                                                             Three Months Ended
                                                                September 30,
                                                            --------------------
                                                              1997        1996
                                                            --------    --------
<S>                                                         <C>         <C>     
Revenues:
   Product Sales                                            $ 20,402    $ 16,785

Costs and expenses:
   Cost of sales                                               6,502       5,145
   Selling, general and administrative                        10,569       8,848
   Research and development                                    5,726       4,162
                                                            --------    --------
                                                              22,797      18,155
                                                            --------    --------

Loss from operations                                          (2,395)     (1,370)

Other income (expense):
   Net gain on investments, principally Boston Scientific
     Corporation (Target Therapeutics, Inc. in fiscal 1997)    5,932       6,184
   Equity in losses of affiliates, net                           (73)       (474)
   Interest income                                               301         354
   Interest expense                                              (25)        (85)
                                                            --------    --------

Income before income taxes and minority interest               3,740       4,609

Provision for income taxes                                     1,758       2,443
Minority interest                                                (28)       (141)
                                                            --------    --------

Net income                                                  $  2,010    $  2,307
                                                            ========    ========

Net income per share                                        $    .23    $    .25
                                                            ========    ========

Shares used in calculating per share information               8,901       9,086
                                                            ========    ========
</TABLE>


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                              COLLAGEN CORPORATION
                 CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                Increase (Decrease) in Cash and Cash Equivalents
                                   (Unaudited)
                                 (In thousands)

<TABLE>
<CAPTION>
                                                                                 Three Months Ended
                                                                                    September 30,
                                                                                --------------------
                                                                                  1997        1996
                                                                                --------    --------
<S>                                                                             <C>         <C>     
Cash flows from operating activities:
   Net income                                                                   $  2,010    $  2,307
   Adjustments to reconcile net income to net cash provided by
    (used in) operating activities:
      Depreciation and amortization                                                1,730       1,617
      Equity in losses of affiliates                                                  73         474
      Gain on investments, net of taxes paid of $0 and $3.5 million
        in fiscal 1998 and 1997, respectively                                     (5,932)     (2,702)
      Other adjustments related to changes in
        assets and liabilities                                                    (2,289)      1,560
                                                                                  -------     ------
    Net cash provided by (used in) operating activities                           (4,408)      3,256
                                                                                  -------     ------

Cash flows from investing activities:
   Proceeds from sale of Boston Scientific Corporation stock
    (Target Therapeutics, Inc. in Fiscal 1997), net of taxes paid                  6,216       3,767
   Proceeds from sale of other affiliate stock                                       704          --
   Proceeds from sales and maturities of short-term investments                    2,650         500
   Purchases of short-term investments                                            (5,324)     (2,865)
   Expenditures for property and equipment                                        (1,414)     (1,704)
   Increase in intangible and other assets                                            --         (46)
   Expenditures for investments in and loans to affiliates, net of repayments         44      (1,255)
                                                                                --------    --------
    Net cash provided by (used in) investing activities                            2,876      (1,603)
                                                                                --------    --------

Cash flows from financing activities:
   Repurchase of common stock                                                         --      (2,547)
   Net proceeds from issuance of common stock                                         94         524
   Cash dividends paid                                                              (881)       (885)
   Repayment of bank loans                                                            --         (41)
                                                                                --------    --------
    Net cash used in financing activities                                           (787)     (2,949)
                                                                                --------    --------

Net decrease in cash and cash equivalents                                         (2,319)     (1,296)

Cash and cash equivalents at beginning of period                                  18,481      21,676
                                                                                --------    --------

Cash and cash equivalents at end of period                                      $ 16,162    $ 20,380
                                                                                ========    ========
</TABLE>



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                              COLLAGEN CORPORATION
              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                   (Unaudited)


1.  Summary of Significant Accounting Policies

    Basis of Presentation

    The consolidated financial statements include the accounts of Collagen
    Corporation (the "Company"), a Delaware corporation, and its wholly-owned
    and majority-owned subsidiaries. All significant intercompany accounts and
    transactions have been eliminated. The Company operates in one industry
    segment focusing on the development, manufacturing, and sale of medical
    devices. Investments in unconsolidated subsidiaries, and other investments
    in which the Company has a 20% to 50% interest or otherwise has the ability
    to exercise significant influence, are accounted for under the equity
    method. Investments in companies in which the Company has less than 20%
    interest with either no readily determinable fair value or with transfer
    restrictions are carried at cost or estimated realizable value, if less, and
    those unrestricted investments with a readily determinable fair value are
    carried at market value with the unrealized gains or losses, net of tax, as
    a component of stockholders' equity.

    The consolidated balance sheet as of September 30, 1997, the consolidated
    statements of income for the three months ended September 30, 1997 and 1996,
    and the condensed consolidated statements of cash flows for the three months
    ended September 30, 1997 and 1996, have been prepared by the Company,
    without audit. In the opinion of management, all necessary adjustments
    (which include only normal recurring adjustments) have been made to present
    fairly the financial position, results of operations, and cash flows at
    September 30, 1997 and for all periods presented. Interim results are not
    necessarily indicative of results for a full fiscal year. The consolidated
    balance sheet as of June 30, 1997 has been derived from the audited
    consolidated financial statements at that date.

    Certain information and footnote disclosures normally included in financial
    statements prepared in accordance with generally accepted accounting
    principles have been condensed or omitted. These condensed consolidated
    financial statements should be read in conjunction with the audited
    consolidated financial statements and notes included in the Company's Annual
    Report on Form 10-K for the year ended June 30, 1997.


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<PAGE>   7



2.  Inventories

    Inventories consist of the following (in thousands):



<TABLE>
<CAPTION>
                                      September 30,     June 30,
                                          1997            1997
                                      -------------     --------
<S>                                     <C>             <C>    
                Raw materials           $ 1,231         $   938
                Work-in-process           6,604           7,188
                Finished goods            5,775           6,167
                                        -------         -------
                                        $13,610         $14,293
                                        =======         =======
</TABLE>


3.  Investment in Boston Scientific Corporation

    The Company accounts for its investment in Boston Scientific Corporation
    ("Boston Scientific") as an available-for-sale equity security, which
    accordingly is carried at market value. During the quarter ended September
    30, 1997, the Company sold 87,340 shares of Boston Scientific common stock
    for a pre-tax gain of approximately $5.9 million. Boston Scientific common
    stock is quoted on the New York Stock Exchange under the symbol BSX. The
    closing price of Boston Scientific common stock at September 30, 1997 was
    $55.19 per share. At September 30, 1997, the Company held 1,277,860 shares
    of Boston Scientific common stock and all holding restrictions resulting
    from the acquisition of Target Therapeutics, Inc. by Boston Scientific that
    were applicable at June 30, 1997, had expired. Pursuant to a hedging
    strategy implemented by the Company in mid-August 1997, approximately half
    of the Company's position in Boston Scientific is hedged, utilizing the
    purchase of puts and calls in combination to minimize the downside risk of
    loss should the price of Boston Scientific stock decline while allowing for
    limited upside participation should the stock price rise. The call option is
    collateralized by shares of Boston Scientific common stock held by the
    Company.

    At June 30, 1997 and September 30, 1997, the Company's shares of Boston
    Scientific common stock were recorded at $83.9 and $70.5 million,
    respectively. The $78.0 million unrealized gain ($83.9 million estimated
    fair value less $5.9 million cost) at June 30, 1997 and the $65.0 million
    unrealized gain ($70.5 million estimated fair value less $5.5 million cost)
    at September 30, 1997, on these available-for-sale securities has been
    reported as a separate component of stockholders' equity, net of tax.



4.  Investment in Innovasive Devices, Inc.,

    Prior to October 1996, the Company's 844,000 shares of common stock of
    Innovasive Devices, Inc. ("Innovasive Devices") were valued at cost, or
    $4,064,000, due to restrictions which prevented the sale of any of the
    Company's shares of 



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<PAGE>   8

    common stock of Innovasive Devices. At September 30, 1997, restrictions were
    no longer applicable on 292,000 shares of common stock which the Company
    holds in Innovasive Devices. As a result, the Company now carries the
    non-restricted portion of its investment in Innovasive Devices as an
    available-for-sale investment at market value, or $2.8 million, reflecting
    an unrealized gain of $1.4 million, which has been included in a separate
    component of stockholders' equity, net of tax. The remaining 552,000
    restricted shares of common stock continue to be valued at cost.

    During the three months ended September 30, 1997, the Company did not sell
    any of its shares of common stock of Innovasive Devices. Innovasive Devices
    common stock is quoted on The Nasdaq Stock Market under the symbol IDEA. The
    closing price of Innovasive Devices common stock at September 30, 1997, was
    $9.56 per share. At September 30, 1997, the Company held approximately a 9%
    ownership position in Innovasive Devices.



5.  Income Taxes

    The provision for income taxes for the three months ended September 30, 1997
    and 1996 was computed by applying the estimated annual income tax rates of
    approximately 47% and 53%, respectively, to income before income taxes and
    minority interest. The lower effective tax rate in the current year
    primarily was due to the ability to utilize net operating loss carryforwards
    in certain foreign subsidiaries as a result of these foreign subsidiaries
    generating net income in the current year.



6.  Per Share Information

    Net income per share for the three months ended September 30, 1997 and 1996,
    have been computed based upon the weighted average number of common stock
    and dilutive common stock equivalent shares outstanding. Shares used in the
    per share computations are as follows (in thousands):



<TABLE>
<CAPTION>
                                                             Three Months Ended
                                                               September 30,
                                                            --------------------
                                                            1997           1996
                                                            -----          -----
<S>                                                         <C>            <C>  
Primary:

Common stock                                                8,819          8,963
Stock options                                                  82            123
                                                            -----          -----

Weighted average number of common stock
   and dilutive common stock equivalent shares
   outstanding                                              8,901          9,086
                                                            =====          =====
</TABLE>


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7.  Earnings per share

    In February 1997, the Financial Accounting Standards Board issued Statement
    of Financial Accounting Standards No. 128, Earnings Per Share ("SFAS#128"),
    which is required to be adopted by December 31, 1997. At that time, the
    Company will be required to change the method currently used to compute
    earnings per share and to restate all prior periods. Under the new
    requirements for calculating basic earnings per share, the dilutive effect
    of stock options will be excluded. The impact of SFAS#128 is expected to
    result in no change to the Company's net income per share for the three
    months ended September 30, 1997 compared to an increase of $0.01 per share
    for the three months ended September 30, 1996. The Company does not expect
    the impact on the calculation of the Company's fully diluted earnings per
    share to be material.






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                                   SIGNATURES



Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.





                                                   COLLAGEN CORPORATION





   
Date:  December 19, 1997                           /s/ NORMAN HALLEEN
       -----------------                           --------------------------
    
                                                   Norman Halleen
                                                   Vice President Finance
                                                   Chief Financial Officer





   
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