============================================================================= UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities and Exchange Act of 1934 (Amendment No. 8)* Mentor Corporation ------------------------------------------------ (Name of Issuer) Common Stock, Par Value $0.10 per share ------------------------------------------------ (Title of Class of Securities) 587188103 ------------------------------------------------ (CUSIP Number) Allison Bennington, Esq. ValueAct Capital 435 Pacific Avenue, Fourth Floor San Francisco, CA 94133 (415) 362-3700 ------------------------------------------------ (Name, address and telephone number of Person Authorized to Receive Notices and Communications) Christopher G. Karras, Esq. Dechert LLP Cira Centre 2929 Arch Street Philadelphia, PA 19104-2808 (215) 994-4000 June 5, 2006 ------------------------------------------------ (Date of Event which Requires Filing of this Statement) If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box [ ]. Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 240.13d-7 for other parties to whom copies are to be sent. *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page. This information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). ============================================================================= SCHEDULE 13D -------------------------- ------------------------- CUSIP NO. 587188103 Page 2 of 14 ----------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE PERSON (entities only) ValueAct Capital Master Fund, L.P. ----------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [X] (b) [ ] ----------------------------------------------------------------------------- 3. SEC USE ONLY ----------------------------------------------------------------------------- 4. SOURCE OF FUNDS (See Instructions)* WC* ----------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ----------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION British Virgin Islands ----------------------------------------------------------------------------- 7. SOLE VOTING POWER 0 NUMBER OF ---------------------------------------------------------- SHARES 8. SHARED VOTING POWER BENEFICIALLY 2,022,133** OWNED BY EACH ---------------------------------------------------------- PERSON WITH 9. SOLE DISPOSITIVE POWER 0 ---------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 2,022,133** ----------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,022,133** ----------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES [ ] ----------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.9% ----------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON PN ----------------------------------------------------------------------------- *See Item 3 **See Item 2 and 5 SCHEDULE 13D -------------------------- ------------------------- CUSIP NO. 587188103 Page 3 of 14 ---------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE PERSON (entities only) VA Partners, L.L.C. ----------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [X] (b) [ ] ----------------------------------------------------------------------------- 3. SEC USE ONLY ----------------------------------------------------------------------------- 4. SOURCE OF FUNDS* 00* ----------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ----------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ----------------------------------------------------------------------------- 7. SOLE VOTING POWER 0 NUMBER OF ---------------------------------------------------------- SHARES 8. SHARED VOTING POWER BENEFICIALLY 2,022,133** OWNED BY EACH ---------------------------------------------------------- PERSON WITH 9. SOLE DISPOSITIVE POWER 0 ---------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 2,022,133** ----------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,022,133** ----------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES [ ] ----------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.9% ----------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON 00 (LLC) ----------------------------------------------------------------------------- *See Item 3 **See Item 2 and 5 SCHEDULE 13D -------------------------- ------------------------- CUSIP NO. 587188103 Page 4 of 14 ---------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE PERSON (entities only) ValueAct Capital Management, L.P. ----------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [X] (b) [ ] ----------------------------------------------------------------------------- 3. SEC USE ONLY ----------------------------------------------------------------------------- 4. SOURCE OF FUNDS* 00* ----------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ----------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ----------------------------------------------------------------------------- 7. SOLE VOTING POWER 0 NUMBER OF ---------------------------------------------------------- SHARES 8. SHARED VOTING POWER BENEFICIALLY 2,022,133** OWNED BY EACH ---------------------------------------------------------- PERSON WITH 9. SOLE DISPOSITIVE POWER 0 ---------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 2,022,133** ----------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,022,133** ----------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES [ ] ----------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.9% ----------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON PN ----------------------------------------------------------------------------- *See Item 3 **See Item 2 and 5 SCHEDULE 13D -------------------------- ------------------------- CUSIP NO. 587188103 Page 5 of 14 ---------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE PERSON (entities only) ValueAct Capital Management, LLC ----------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [X] (b) [ ] ----------------------------------------------------------------------------- 3. SEC USE ONLY ----------------------------------------------------------------------------- 4. SOURCE OF FUNDS* 00* ----------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ----------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ----------------------------------------------------------------------------- 7. SOLE VOTING POWER 0 NUMBER OF ---------------------------------------------------------- SHARES 8. SHARED VOTING POWER BENEFICIALLY 2,022,133** OWNED BY EACH ---------------------------------------------------------- PERSON WITH 9. SOLE DISPOSITIVE POWER 0 ---------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 2,022,133** ----------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,022,133** ----------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES [ ] ----------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.9% ----------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON 00 (LLC) ----------------------------------------------------------------------------- *See Item 3 **See Item 2 and 5 SCHEDULE 13D -------------------------- ------------------------- CUSIP NO. 587188103 Page 6 of 14 ----------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE PERSON (entities only) Jeffrey W. Ubben --------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [X] (b) [ ] ----------------------------------------------------------------------------- 3. SEC USE ONLY --------------------------------------------------------------------------- 4. SOURCE OF FUNDS* 00* ----------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ----------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION United States ----------------------------------------------------------------------------- 7. SOLE VOTING POWER 0 NUMBER OF ---------------------------------------------------------- SHARES 8. SHARED VOTING POWER BENEFICIALLY 2,022,133** OWNED BY EACH ---------------------------------------------------------- PERSON WITH 9. SOLE DISPOSITIVE POWER 0 ---------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 2,022,133** ----------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,022,133** ----------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES [ ] ----------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.9% ----------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON IN ----------------------------------------------------------------------------- *See Item 3 **See Item 2 and 5 SCHEDULE 13D -------------------------- ------------------------- CUSIP NO. 587188103 Page 7 of 14 ----------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE PERSON (entities only) George F. Hamel, Jr. --------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [X] (b) [ ] ----------------------------------------------------------------------------- 3. SEC USE ONLY ----------------------------------------------------------------------------- 4. SOURCE OF FUNDS* 00* ----------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ----------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION United States ----------------------------------------------------------------------------- 7. SOLE VOTING POWER 0 NUMBER OF ---------------------------------------------------------- SHARES 8. SHARED VOTING POWER BENEFICIALLY 2,022,133** OWNED BY EACH ---------------------------------------------------------- PERSON WITH 9. SOLE DISPOSITIVE POWER 0 ---------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 2,022,133** ----------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,022,133** ----------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES [ ] ----------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.9% ----------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON IN ----------------------------------------------------------------------------- *See Item 3 **See Item 2 and 5 SCHEDULE 13D -------------------------- ------------------------- CUSIP NO. 587188103 Page 8 of 14 ----------------------------------------------------------------------------- 1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE PERSON (entities only) Peter H. Kamin ----------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [X] (b) [ ] --------------------------------------------------------------------------- 3. SEC USE ONLY ----------------------------------------------------------------------------- 4. SOURCE OF FUNDS* 00* ----------------------------------------------------------------------------- 5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ----------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION United States ----------------------------------------------------------------------------- 7. SOLE VOTING POWER 0 NUMBER OF ---------------------------------------------------------- SHARES 8. SHARED VOTING POWER BENEFICIALLY 2,022,133** OWNED BY EACH ---------------------------------------------------------- PERSON WITH 9. SOLE DISPOSITIVE POWER 0 ---------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 2,022,133** ----------------------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,022,133** ----------------------------------------------------------------------------- 12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES [ ] ----------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.9% ----------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON IN ----------------------------------------------------------------------------- *See Item 3 **See Item 2 and 5 THE PURPOSE OF THIS AMENDMENT NO. 8 TO SCHEDULE 13D IS TO AMEND THE OWNERSHIP REPORTS OF THE REPORTING PERSONS. THE INFORMATION BELOW SUPPLEMENTS THE INFORMATION PREVIOUSLY PROVIDED. Item 1. Security and Issuer This Schedule 13D relates to shares of Common Stock, par value $0.10 par value per share (the "Common Stock"), of Mentor Corporation, a Minnesota corporation (the "Issuer"). The address of the principal executive offices of the Issuer is 201 Mentor Drive, Santa Barbara, California, 93111. Item 2. Identity and Background This statement is filed jointly by (a) ValueAct Capital Master Fund, L.P. ("ValueAct Master Fund"), (b) VA Partners, L.L.C. ("VA Partners"), (c) ValueAct Capital Management, L.P. ("ValueAct Management L.P. "), (d) ValueAct Capital Management, LLC ("ValueAct Management LLC"), (e) Jeffrey W. Ubben, (f) George F. Hamel, Jr. and (g) Peter H. Kamin (collectively, the "Reporting Persons"). ValueAct Master Fund is a limited partnership organized under the laws of the British Virgin Islands. ValueAct Master Fund has a principal business address of 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133. VA Partners is a Delaware limited liability company, the principal business of which is to serve as the General Partner to ValueAct Master Fund. VA Partners has a principal business address of 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133. ValueAct Management L.P. is a Delaware limited partnership which renders management services to ValueAct Master Fund. ValueAct Management LLC is a Delaware limited liability company, the principal business of which is to serve as the General Partner to ValueAct Management L.P. Each has a principal business address of 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133. (a), (b) and (c). Messrs. Ubben, Hamel and Kamin are each managing members, principal owners and controlling persons of VA Partners and ValueAct Management LLC, and such activities constitute their principal occupations. Such individuals are sometimes collectively referred to herein as the "Managing Members" or individually as a "Managing Member". Each Managing Member is a United States citizen and has a principal business address of 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133. (d) and (e). None of the entities or persons identified in this Item 2 has during the past five years been convicted of any criminal proceeding (excluding traffic violations or similar misdemeanors), nor been a party to a civil proceeding of a judicial or administrative body of competent judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws. Page 9 of 14 ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION. Not applicable in that transaction involved the sale of and not the acquisition of securities. Item 5. Interest in Securities of the Issuer (a) and (b). Set forth below is the beneficial ownership of shares of Common Stock of the Issuer for each person named in Item 2. Shares reported as beneficially owned by ValueAct Master Fund are also reported as beneficially owned by (i) VA Partners, as General Partner of each such investment partnership,(ii) ValueAct Management L.P. as the manager of each such investment partnership, (iii) ValueAct Management LLC, as General Partner of ValueAct Management L.P. and (iv) the Managing Members as controlling persons of VA Partners and ValueAct Management LLC. VA Partners, ValueAct Management LLC and the Managing Members also, directly or indirectly, may own interests in one or more than one of the partnerships from time to time. Unless otherwise indicated below, by reason of such relationships ValueAct Master Fund is reported as having shared power to vote or to direct the vote, and shared power to dispose or direct the disposition of, such shares of Common Stock, with VA Partners, ValueAct Management L.P., ValueAct Management LLC and the Managing Members. As of the date hereof, ValueAct Master Fund is the beneficial owner of 2,022,133 shares of Common Stock, representing approximately 4.9% of the Issuer's outstanding Common Stock. VA Partners, ValueAct Management L.P., ValueAct Management LLC and the Managing Members may each be deemed the beneficial owner of an aggregate of 2,022,133 shares of Common Stock, representing approximately 4.9% of the Issuer's outstanding Common Stock. All percentages set forth in this Schedule 13D are based upon the Issuer's reported 41,319,261 outstanding shares of Common Stock. (c) During the sixty (60) days preceding the date of this report, the Reporting Persons sold the following shares of Common Stock: Reporting Person Trade Date Shares Price/Share ---------- --------- ------- ----------- ValueAct Master Fund 06/05/2006 61,200 $42.58 06/05/2006 2,000,000* $42.00 *Shares sold by the Reporting Persons in a private sale to the Issuer. (d) Not applicable. (e) As of June 5, 2006 the Reporting Persons ceased to be the beneficial owners, in the aggregate, of more than five percent of Issuer Common Stock, and accordingly, their obligation to file a Schedule 13D has been terminated. Page 10 of 14 Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer Other than as described elsewhere in this Report and as previously reported, the Reporting Persons have no understandings, arrangements, relationships or contracts relating to the Issuer's Common Stock which are required to be described hereunder. Item 7. Material to Be Filed as Exhibits (1) Joint Filing Agreement. Page 11 of 14 SIGNATURE After reasonable inquiry and to the best of his knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct. POWER OF ATTORNEY KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below on this Schedule 13D hereby constitutes and appoints Jeffrey W. Ubben, George F. Hamel, Jr. and Peter H. Kamin, and each of them, with full power to act without the other, his or its true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for him or it and in his or its name, place and stead, in any and all capacities (until revoked in writing) to sign any and all amendments to this Schedule 13D, and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary fully to all intents and purposes as he or it might or could do in person, thereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof. ValueAct Capital Master Fund L.P., by VA Partners, L.L.C., its General Partner By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member VA Partners, L.L.C. By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member ValueAct Capital Management, L.P., by ValueAct Capital Management, LLC its General Partner By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member ValueAct Capital Management, LLC By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member Page 12 of 14 By: /s/ Jeffrey W. Ubben -------------------------------------- Dated: June 7, 2006 Jeffrey W. Ubben, Managing Member By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member By: /s/ Peter H. Kamin -------------------------------------- Dated: June 7, 2006 Peter H. Kamin, Managing Member Page 13 of 14 Exhibit 1 JOINT FILING UNDERTAKING The undersigned parties hereby agree that the Schedule 13D filed herewith (and any amendments thereto) relating to the Common Stock of Mentor Corporation is being filed jointly on behalf of each of them with the Securities and Exchange Commission pursuant to Section 13(d) of the Securities Exchange Act of 1934, as amended. ValueAct Capital Master Fund L.P., by VA Partners, L.L.C., its General Partner By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member VA Partners, L.L.C. By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member ValueAct Capital Management, L.P., by, ValueAct Capital Management, LLC its General Partner By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member ValueAct Capital Management, LLC By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member By: /s/ Jeffrey W. Ubben -------------------------------------- Dated: June 7, 2006 Jeffrey W. Ubben, Managing Member By: /s/ George F. Hamel, Jr. -------------------------------------- Dated: June 7, 2006 George F. Hamel, Jr., Managing Member By: /s/ Peter H. Kamin -------------------------------------- Dated: June 7, 2006 Peter H. Kamin, Managing Member Page 14 of 14