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                                                                    EXHIBIT 10.7

                                   PRESBY CORP
                               CONFIDENTIALITY AND
                     INTELLECTUAL PROPERTY RIGHTS AGREEMENT
                                   (EMPLOYEE)

     As an employee of Presby Corp, a Delaware corporation (the "Company"), the
undersigned ("Employee"), for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, does hereby enter into this
CONFIDENTIALITY AND INTELLECTUAL PROPERTY RIGHTS AGREEMENT (this "Agreement") as
of the 23rd day of July, 1997, with and for the benefit of the Company.

1.   DEFINITIONS. In addition to the capitalized terms defined throughout this
Agreement, the following terms shall have the meanings provided below:

          (a) "CONFIDENTIAL INFORMATION" shall mean information or material
proprietary to the Company and not generally known outside the Company,
including without limitation information conceived, originated, discover or
developed in whole or in part, or otherwise obtained, by Employee. Confidential
Information includes, but is not limited to, the following types of information
and other information of a similar nature (whether or not reduced to writing):
discoveries, ideas, inventions, concepts, software in any and all stages of
development, designs, drawings, specifications, techniques, methods, models,
schematics, data, source code, object code, source listings, program listings,
documentation, diagrams, flow charts, research, development, processes,
procedures, formulae, "know-how", marketing techniques and materials, marketing
and development plans, business plans and strategies, customer names and other
information related to customers, supplier lists, price lists, pricing policies,
financial information, employee files, Intellectual Property (as defined
hereinafter) and other proprietary rights. Confidential Information also
includes any information described above which the Company obtains from another
party and treats as proprietary or designates as "Proprietary," "Confidential"
or other similar markings, whether or not owned or developed by the Company.
Confidential Information does not include information that, without restriction
on it use, is: (i) generally known or available by publication, commercial use
or otherwise, or enters the public domain, through no fault of Employee; (ii)
known and has been reduced to tangible form by Employee prior to the time of
disclosure to Employee; or (iii) independently developed by Employee outside the
scope of Employee's employment by the Company and without reference to any
Confidential Information, and is in no manner related to the Company's prior,
current or prospective business opportunities.

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          (b) "INTELLECTUAL PROPERTY" shall mean any and all rights, title and
interest under any and all domestic or foreign patents, copyrights, trade
secrets, mask works, trademarks, trade names and service marks, including
without limitation all rights to apply therefor, in any inventions, discoveries,
improvements, works of authorship, confidential information and know-how and
other similar intellectual property rights recognized under the laws of any
country or jurisdiction.

2.   DISCLOSURE AND USE OF CONFIDENTIAL INFORMATION

     2.1  DISCLOSURE. At all times during and after Employee's employment with
the Company, Employee agrees to keep the Confidential Information in confidence
and, absent prior written consent of the Company, agrees not to disclose or
provide access to the same to anyone other than officers, directors, authorized
employees or other authorized agents of the Company, either directly or
indirectly. Employee further agrees not to disclose the Confidential Information
to any person employed by or contracting with the Company except as reasonably
necessary in connection with the performance of Employee's services for the
Company.

     2.2  USE. Employee agrees to use the Confidential Information only as
reasonably necessary in connection with the performance of Employee's services
for the Company, and agrees not to use the Confidential Information for any
purpose other than for the Company's business, or permit any third person to use
the Confidential Information, either during or after Employee's employment with
the Company, in any way or for any purpose, except at the request of and for the
benefit of the Company.

     2.3  NOTIFICATION. Employee shall notify the Company promptly and in
writing of any circumstances of which Employee has knowledge relating to any
possession or use of the Confidential Information, or any part thereof, by any
person or entity other than those authorized by the terms of this Agreement.

     2.4  FURTHER ACTS. Employee shall take any and all other actions reasonably
deemed necessary or appropriate by the Company from time to time in its sole
discretion to ensure the continued confidentiality and protection of the
Confidential Information.

     2.5  OWNERSHIP OF MATERIALS AND THE LIKE. Employee agrees that the
Confidential Information and all notes, data, reference materials, sketches,
drawings, memoranda, documentation and records in any way incorporating or
reflecting any of the Confidential Information and all proprietary rights
therein including, without limitation, any copyrights,

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shall at all times be and remain the sole and exclusive property of the Company,
and Employee agrees to turn over to the Company all copies of such materials in
Employee's possession or control upon request or upon termination of Employee's
employment with the Company for whatever reason.

     2.6  THIRD PARTY RIGHTS. Employee agrees not to directly or indirectly
disclose in any manner to the Company, or improperly use in any business or
activity related to the Company or work therefor, or cause the Company to use in
any way, any information or material which is confidential to any third party,
with the exception of any information or material which the Company is licensed
and permitted to obtain and use from its owner, and after written approval of
such disclosure or use by the Company.

3.   ACKNOWLEDGEMENT OF OWNERSHIP OF INTELLECTUAL PROPERTY RIGHTS

     3.1  OWNERSHIP OF INTELLECTUAL PROPERTY. Employee hereby agrees that all
Intellectual Property and rights thereto and therein relating in any manner to
work performed by or for Employee as part of the performance of Employee's
service to the Company shall be owned exclusively by the Company, and that the
Company may, in its sole discretion, take whatever steps necessary and
appropriate to protect and enforce such Intellectual Property and rights
therein. Furthermore, without limiting the foregoing, any such Intellectual
Property created by Employee and related to the actual or proposed business of
the Company shall be deemed "works made for hire" and the Company shall be
deemed the author thereof under the U.S. Copyright Act (Title 17 of the U.S.
Code).

     3.2  ACKNOWLEDGEMENT OF OWNERSHIP. Employee hereby acknowledges that
Employee does not own, has not acquired and does not control, nor does Employee
claim any ownership or other interest in, any part of the Intellectual Property,
or any rights therein. Furthermore, to the extent that some or all of the
Intellectual Property is determined not to constitute "works made for hire," as
a matter of law, Employee hereby agrees to irrevocably assign, transfer, convey
and quitclaim to the Company, without any separate or additional remuneration or
compensation, all right, title and interest in and to any such Intellectual
Property.

     3.3  DISCLOSURE. Employee agrees to promptly disclose to the Company, and
the Company hereby agrees to receive all such disclosures in confidence, any
invention, computer program and related architecture and developments,
modification, discovery, design, development, improvement, process, system,
formula, data, technique, writing,

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know-how, secret or any intellectual property or proprietary right or any
interest therein made, conceived, discovered, developed, written, reduced to
practice or acquired or possessed by Employee (either alone or with others) at
any time or times during Employee's employment with the Company or thereafter
for the purpose of determining whether they constitute Intellectual Property for
the purpose of this Agreement.

     3.4  PERFORMANCE OF OTHER ACTS. From the date hereof and at any time
thereafter, and at the request and expense of the Company, Employee agrees to
sign or execute any and all documents, and perform any and all such acts as the
Company and its duly authorized agents may reasonably require: (a) to apply for,
obtain, and vest in the name of the Company alone (unless the Company otherwise
directs) letters patent, copyrights, trademarks or other analogous protection
for any Intellectual Property in any country throughout the world and when so
obtained or vested to maintain, renew and restore the same; (b) to assist, as
required by the Company, in the defense of any opposition proceedings in respect
to such applications and any opposition proceedings, petitions, applications or
litigation for revocation or invalidation of such letters patent, copyright or
trademarks or other analogous protection; and (c) to effectuate the vesting in
the name of the Company alone (unless the Company otherwise directs) of the
ownership, title and interest of any item of Intellectual Property.

4.   GENERAL PROVISIONS

     4.1  TERM OF OBLIGATIONS: SURVIVAL. The obligation set forth in this
Agreement shall terminate upon the termination of Employee's employment with the
Company, with the exception that Sections 1, 2, 3, 4.1, 4.3, 4.4, 4.5, 4.7, and
4.8 hereof shall survive such termination and remain effective, enforceable, and
binding upon Employee and Employee's heirs and successors in interest subsequent
to such termination.

     4.2  NON-COMPETE. During the period of Employee's employment with the
Company, Employees shall not directly or indirectly, engage, participate, or
make any financial investment (other than a passive investment), in, or become
employed by or render advisory or other services to or for any Person (within
the meaning of Section 13(d) and 14(d) of the Securities Exchange Act of 1934,
as amended) or other business enterprise which engaged, directly or indirectly,
in competition with the Company or any of its subsidiaries.

     4.3  NONSOLICITATION. During the period of Employee's employment with the
Company and for two (2) years thereafter, Employee agrees not to directly or
indirectly

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solicit, interfere with the Company's relationships with, or entice away from
the Company, any customer, licensee, licensor, distributor, representative,
employee, contractor or source of supply of the Company.

     4.4  INJUNCTIVE RELIEF. Employee acknowledges that because of the unique
nature of the Confidential Information and the Intellectual Property, the
Company will suffer irreparable harm and significant injury in the event that
Employee breaches any of the terms of this Agreement, and that monetary damages
will be difficult to ascertain and inadequate to compensate the Company for such
breach. Accordingly, Employee agrees that the Company will, in addition to any
other remedies available to it at law or in equity, be entitled to injunctive
relief to enforce the terms of this Agreement. Nothing herein shall be construed
as prohibiting the Company from pursuing other remedies available to it for such
breach or threatened breach, including the recovery of damages.

     4.5  ASSIGNMENT. This Agreement may be assigned, in whole or in part, by
the Company to any third party and shall inure to the benefit of any and all of
the Company's successors and assigns. However, because of the unique and
personal nature of the services of Employee which form at least a part of
Employee's employment with the Company, Employee may not assign any of his
obligations, or portions thereof, under this Agreement.

     4.6  GOVERNING LAW. This Agreement shall be governed by and construed in
accordance with the laws of the State of Texas.

     4.7. SEVERABILITY; WAIVER. If any provision or any obligation or grant of
rights forming a part of this Agreement shall be held by a court of competent
jurisdiction to be invalid or otherwise unenforceable, the remaining provisions
of this Agreement shall remain in full force and effect. No delay or omission by
either party hereto to exercise any right or power hereunder shall impair such
right or power or be construed to be a waiver thereof. A waiver by either of the
parties hereto of any of the covenants to be performed by the other or any
breach thereof shall not be construed to be a waiver of any succeeding breach
thereof or of any other covenant herein contained.

     4.8  ENTIRE AGREEMENT. This Agreement constitutes the full and complete
understanding of the parties with respect to the subject matter hereof, and
supersedes all oral or written communications, understandings or agreements
concerning the Confidential Information and the Intellectual Property. This
Agreement may not be amended, modified or supplemented except by written
agreement signed by both parties hereto.

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     THE UNDERSIGNED hereby agrees to the above terms and acknowledges receipt
of a copy hereof by executing this Agreement in the space provided below as of
the date first written above.

Signature:       /s/ Mark A. Cox
                 -----------------------------

Name:            Mark A. Cox

Mailing Address: 9418 Rocky Branch Drive
                 Dallas, Texas 74243

Accepted and Acknowledged
as of the 23rd day of July, 1997

PRESBY CORP

By: /s/ Ronald A. Schachar
    -----------------------------
Name: Ronald A. Schachar, M.D.
      ---------------------------
Title: President
       --------------------------

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