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                                                                    EXHIBIT 10.4

                                SECRECY AGREEMENT

     THIS SECRECY AGREEMENT ("Agreement") is made and entered into effective as
of the 21st day of August, 2001, by and between CIBA Vision Corporation, a
Delaware corporation with offices located at 11460 Johns Creek Parkway, Duluth,
Georgia 30097 ("CV"), RAS Holding Corp. ("RAS Holding") and Presby Corp.
("Presby"), corporations with offices located at 5910 North Central Expressway,
Suite 1770, Dallas, TX 75206 (collectively, "PC").

                                   WITNESSETH:

     WHEREAS, CV and PC respectively possess certain confidential information
and data and are willing to disclose such confidential information and data to
each other pursuant to the terms and subject to the conditions hereinafter set
forth;

     NOW THEREFORE, for and in consideration of the premises, and the mutual
covenants, representations and warranties hereinafter set forth, the adequacy
and sufficiency of which are hereby acknowledged, the parties agree as follows:

     1.   For the purpose of enabling the parties to enter into discussions
relating to a possible future business relationship, CV may disclose to PC
certain confidential information and data relating to its business including,
but not limited to, products, product design, product formulations, and product
research and development; vendors and customers; manufacturing techniques and
methods of operation; regulatory and legal matters; marketing strategies;
business operations and financial results; future plans and other competitively
sensitive information; and, PC may disclose to CV certain confidential
information and data relating to its business, including but not limited to,
products, product design, product formulations, and product research and
development; vendors and customers; manufacturing techniques and methods of
operation; regulatory and legal matters; marketing strategies; business
operations and financial results; future plans and other competitively sensitive
information. All confidential information and data disclosed by either party to
the other shall constitute "Confidential Information" of the disclosing party.

     2.   For a period of five (5) years after the date of disclosure, CV and PC
shall:

          (a)  make no use of any of the Confidential Information belonging to
     the other except for the purpose stated in the foregoing paragraph 1;

          (b)  not disclose or transfer in any form to any third parties any of
     the Confidential Information belonging to the other without the express
     prior written consent of the other, except that either party may disclose
     the Confidential Information to affiliates and consultants pursuant to a
     nondisclosure commitment; and

          (c)  not disclose or transfer the Confidential Information to any of
     its officers, employees, agents and representatives except those who are
     required to be aware of it for

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     the purpose stated in the foregoing paragraph 1 and who are bound not to
     disclose it by obligations of confidentiality.

     3.   Notwithstanding any of the foregoing, the obligations of nonuse and
nondisclosure hereunder shall not apply to any Confidential Information that the
party seeking nonapplicability can show by competent proof:

     (a)  was generally known to the public at the time of disclosure by the
     other party;

     (b)  becomes generally known to the public after disclosure by the other
     party, through no act or omission of the party seeking nonapplicability or
     its officers, employees, agents, or representatives;

     (c)  was disclosed to the party seeking nonapplicability, prior or
     subsequent to the time of disclosure by the other party, by a third party
     having a bona fide right both to possess the information and to disclose
     the information to the party seeking nonapplicability; or

     (d)  is required by law to be disclosed by the party seeking
     nonapplicability, in which case, the party seeking nonapplicability shall
     give prompt written notice of such requirement to the other party so as to
     allow the other party an opportunity to object to such requirement.

     4.   CV and PC shall deliver to each other or destroy, promptly upon each
other's respective requests, at the requesting party's option, all originals,
copies and excerpts of, and all notes and correspondence incorporating, the
Confidential Information whether in the possession of CV or PC or their
respective agents or representatives. Upon completion of the delivery or the
destruction, as the case may be, the recipient of such request shall deliver to
the requesting party written certification of same signed by a duly authorized
representative.

     5.   Neither party shall, without the other party's express prior written
consent, disclose in any form to any third parties (except to affiliates and
consultants of either party) the substantive content of this Agreement or of any
discussions between them.

     6.   CV and PC represent and warrant to each other that they own and are
free to disclose to each other their respective Confidential Information
pursuant to the terms of this Agreement.

     7.   Each party hereto acknowledges, understands and agrees that a breach
of this Agreement will cause irreparable injury to the other, and that no
adequate or complete remedy at law is available to either party hereto for such
breach. Accordingly, each party hereto agrees that the other shall be entitled
to enforcement of this Agreement by injunction, and hereby irrevocably waives
any defense based on the adequacy of the remedy at law which might be asserted
as a bar to said injunctive relief.

     8.   The provisions of this Agreement shall be construed and enforced in
accordance with the internal law of the State of Georgia.

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     9.   This Agreement shall be binding upon and shall inure to the benefit of
the parties and their respective successors, assigns and legal representatives.

     10.  The parties acknowledge the existence of a letter agreement between CV
and RAS Holding dated May 5, 1999 (the "Prior Agreement"), governing the
confidential treatment of certain information of RAS Holding and its
subsidiaries Presby, PC Lens Corp. and Medical Internet Technologies, Inc.
disclosed to CV. The parties further acknowledge that this Agreement does not
affect the enforceability of the Prior Agreement with respect to disclosures
made by RAS or its subsidiaries Presby, PC Lens Corp. and Medical Internet
Technologies, Inc. prior to the date hereof. This Agreement constitutes the
entire agreement between the parties hereto and supersedes all prior agreements
between the parties hereto with respect to the disclosure of Confidential
Information from and after the date hereof. No change or modification of this
Agreement shall be valid or binding on the parties hereto unless made in a
writing signed by the parties hereto.

     11.  Nothing contained herein shall be construed as granting or conferring
any rights, by license or otherwise, in any Confidential Information disclosed
hereunder.

     12.  As used herein: the term "affiliates" means corporations, partnerships
or other business entities, and the employees and agents thereof, which,
directly or indirectly, are controlled by, control, or are under common control
with, either party.

     IN WITNESS WHEREOF, the parties hereto by their duly authorized
representatives have executed this Agreement as of the date first above written.

CIBA VISION CORPORATION                            RAS HOLDINGCORP

By:    /s/ Daniel H. White                         By:    /s/ Mark A. Cox
       --------------------------                         --------------------
Name:  Daniel H. White                             Name:  Mark A. Cox
       --------------------------                         --------------------
Title: Director, Bio. Dev. & Lic.                  Title: Vice President & CFO
       --------------------------                         --------------------
       CIBA Vision
       --------------------------                         --------------------

                                                   PRESBY CORP

                                                   By:    /s/ Mark A. Cox
                                                          --------------------
                                                   Name:  Mark A. Cox
                                                          --------------------
                                                   Title: Vice President & CFO
                                                          --------------------

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