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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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                                                                    EXHIBIT 10.8

                                  PRESBY CORP.

                   EMPLOYMENT AGREEMENT WITH TERENCE A. WALTS

     This Employment Agreement (this "AGREEMENT") is made and entered into as of
September 5, 2002, by and between Presby Corp., a Delaware corporation (the
"COMPANY"), and Terence A. Walts (the "EXECUTIVE").

     The Company hereby agrees to employ the Executive and the Executive hereby
accepts employment, on the terms and conditions hereinafter set forth.

     l.     PERIOD OF EMPLOYMENT. The period of the Executive's employment (the
"PERIOD OF EMPLOYMENT") shall begin on September 1, 2002 and expire on September
1, 2004, subject to any earlier termination of the Executive's employment as
provided in Section 6 hereof. If the Executive's employment is terminated
pursuant to Section 6 hereof, the Period of Employment shall expire as of the
Date of Termination (as hereinafter defined). The Company shall provide written
notice to the Executive no later than March 5, 2004 of whether the Company
intends to continue to employ the Executive after the expiration of this
Agreement on September 1, 2004.

     2.     DUTIES.

     (a)    The Executive agrees to serve as President and Chief Executive
Officer of the Company, with all duties and authority necessary or appropriate
to carry out properly the responsibilities of such position, as instructed from
time to time by the Company's Board of Directors. During the Period of
Employment, the Executive will devote his full working time and use his best
efforts to advance the business and welfare of the Company. During the Period of
Employment, the Executive shall not engage in any other employment activities
(which, subject to other restrictions contained herein, shall not include solely
passive investments), or serve as a director of any other entity, for any direct
or indirect remuneration without the prior written consent of the Company;
PROVIDED, HOWEVER, that the Executive shall be permitted to continue to serve as
a director of and/or a consultant to (but not an employee of) Oncose, Inc. so
long as the Executive devotes no more than ten percent (10%) of his time to
Oncose-related matters and such matters do not interfere with the Executive's
responsibilities to the Company, including but not limited to his attendance at
all "road show" and related functions. The Executive will terminate his
involvement with Oncose as part-time consultant on December 31, 2002. If
Employee has not terminated his consultant relationship with Oncose by December
31, 2002, Employee shall have the right to extend this consultant relationship
for an additional 90 days.

     (b)    The Executive may also be appointed or elected to serve as a member
of the Company's Board of Directors.

     3.     COMPENSATION.

     (a)    During the Initial Period (as defined below), the Company shall pay
the Executive a salary at the rate of one hundred sixty thousand dollars
($160,000) per year, payable in

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increments at least as frequently as twice per month. Following the Initial
Period, the Company shall pay the Executive a salary at the rate of two hundred
thousand dollars ($200,000) per year, payable in increments at least as
frequently as twice per month. The applicable amount of such salary shall be
referred to as the "BASE SALARY".

     (b)    Compensation shall be subject to review by the Company at the end of
each of the Company's fiscal years during the Period of Employment, provided
that the amount of Base Salary may not be decreased during the Period of
Employment without the written consent of the Executive (it being acknowledged
that the consent of the holders of the Company's Series B Convertible Preferred
Stock (the "SERIES B PREFERRED STOCK") may be required for a change to
compensation paid to the Executive).

     (c)    For the purpose of this Agreement, "INITIAL PERIOD" shall mean the
period of time beginning on September 1, 2002 and ending on the date of a
"CLOSING", which shall mean the date on which the Company closes the sale of
common stock, or securities convertible into common stock, in an offering (other
than an offering relating solely to a transaction under Rule 145 under the
Securities Act of 1933, as amended, or to an employee benefit plan of the
Company), in which the aggregate gross proceeds to the Company are equal to or
greater than ten million dollars ($10,000,000).

     (d)    The Executive may receive a bonus on an annual basis based on the
performance of the Executive and the Company, as may be determined in the sole
discretion of the Company's Board of Directors.

     4.     BENEFITS.

     (a)    During the Period of Employment, the Executive shall be entitled to
participate in the Company's 401(k), group health, dental, disability, life
insurance and other benefit plans applicable to executive officers of the
Company, if any. The Executive shall be entitled to up to four (4) weeks of paid
vacation each calendar year. The Executive shall also be entitled to all paid
holidays and personal days given by the Company to its employees generally.

     (b)    The Executive shall be entitled to stock options as provided in the
Non-Qualified Stock Option Agreement (the "OPTION AGREEMENT") with the Company
dated as of the date hereof.

     5.     EXPENSES. The Company will pay or reimburse the Executive for such
reasonable travel or other expenses as he may incur at the request of the
Company during the Period of Employment in connection with the performance of
his duties hereunder but only to the extent that the Executive (i) furnishes the
Company with evidence of such expenses as the Company may reasonably require to
substantiate such expenses for tax purposes and (ii) complies with other
policies of the Company as may relate to reimbursement of expenses. Expenses
shall include expenses incurred by the Executive in commuting to the Company's
principal place of business in Dallas, Texas, subject to appropriate expense
controls, including but not limited to class of travel and detailed reporting
requirements, agreed to in writing by the Executive and the Company.

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     6.     TERMINATION OF EMPLOYMENT.

     6.1    BY THE COMPANY. Notwithstanding the terms set forth in Section 1
hereof, the Executive's employment with the Company shall terminate upon the
occurrence of any of the following circumstances:

     (a)    DEATH. Immediately upon the Executive's death.

     (b)    PERMANENT DISABILITY. Ten (10) days after written notice to the
Executive that he has suffered a Disability (as defined below). "DISABILITY"
shall mean any illness or impairment of mind or body that (i) renders it
impossible or impracticable for the Executive to perform his duties and
responsibilities hereunder for one hundred eighty (180) consecutive days or (ii)
is likely to prevent the Executive from performing his duties and
responsibilities hereunder for more than six (6) months during any twelve (12)
month period, each as determined in good faith by a physician selected by the
Company's Board of Directors. The selection of a physician shall be subject to
the Executive's (or, if the Executive is mentally incapacitated to such extent
that he cannot so consent, his representative's) approval, which shall not be
unreasonably withheld or delayed. Any refusal without reasonable cause by or
because of physical inability of the Executive to submit to a medical exam for
the purpose of certifying his Disability shall be deemed to constitute
conclusive evidence of the Executive's Disability.

     (c)    CAUSE. At the option of the Company, and as determined in good faith
in the sole discretion of the Board of Directors of the Company, because the
Executive:

     (i)    has been convicted of or entered a plea of guilty or nolo contendere
to a felony, or

     (ii)   has used any non-prescribed controlled or illegal substance (whether
on or off the job), or

     (iii)  has embezzled or misappropriated funds or material property or
engaged in any other material act of dishonesty, fraud, or misconduct, or

     (iv)   has materially violated any provision in this Agreement or any other
agreement between the Executive and the Company, provided that (A) the Company
has provided the Executive with a Notice of Termination (as defined below) and
(B) the Executive has not cured such violation within ten (10) days after such
Notice of Termination is delivered, or

     (v)    has failed or refused to devote his full time and use his best
efforts to perform his duties on behalf of the Company in accordance with this
Agreement, provided that (A) the Company has provided the Executive with a
Notice of Termination and (B) the Executive has not cured such violation within
ten (10) days after such Notice of Termination is delivered, or

     (vi)   has engaged in conduct that constitutes gross neglect or willful
misconduct in carrying out the Executive's duties as an employee, resulting, in
either case, in material economic harm to the Company, other than any act or
omission which in the Executive's reasonable and good faith belief was in or not
opposed to the best interests of the Company.

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     (d)    NOT FOR CAUSE. At the option of the Company at any time for any
reason other than those referred to above or for no reason at all.

     6.2    BY THE EXECUTIVE. The Executive may terminate his employment
hereunder at any time on thirty (30) days' prior written notice to the Company.

     6.3    NOTICE OF TERMINATION. Any termination of the Executive's employment
by the Company (other than termination pursuant to Section 6.1(a) hereof) or by
the Executive shall be communicated by written Notice of Termination to the
other party hereto. For purposes of this Agreement, a "NOTICE OF TERMINATION"
shall mean a notice which shall indicate the specific termination provision in
this Agreement relied upon. For purposes of this Agreement, the "DATE OF
TERMINATION" shall be the date on which the Notice of Termination is delivered,
except that with respect to Section 6.1(a) the Date of Termination shall be the
date of the Executive's death; with respect to Section 6.1(b) the Date of
Termination shall be ten (10) days after the written notice referenced therein;
with respect to Section 6.1(c) the Date of Termination shall be the later of (i)
the date on which the Notice of Termination is delivered or (ii) the date on
which the cure period, if any, expires; and with respect to Section 6.2, thirty
(30) days from the date on which the Notice of Termination is delivered.

     6.4    EFFECT OF TERMINATION ON DIRECTORSHIP. The Executive hereby agrees
that, if he is appointed or elected to serve as a member of the Company's Board
of Directors (or any affiliate or subsidiary of the Company), he shall be deemed
to have resigned automatically as a director effective on the Date of
Termination, in connection with any termination of the Executive's employment by
the Company, pursuant to Section 6.1 or 6.2 or otherwise.

     7.     PAYMENTS UPON TERMINATION OF EMPLOYMENT.

     7.1    COMPENSATION AND BENEFITS.

     (a)    In the event that Executive's employment is terminated under Section
6.1(a) or (c), the Period of Employment shall expire as of the Date of
Termination and the Company shall have no further obligation to provide any
compensation or other consideration, including any Bonus not due prior to the
Date of Termination.

     (b)    In the event that Executive's employment is terminated under Section
6.1(b) or (d) hereof during the Initial Period, the Period of Employment shall
expire as of the Date of Termination and the Executive shall be entitled to
monthly severance payments in the amount of $13,333.33 for a period of three (3)
months.

     (c)    In the event that Executive's employment is terminated under Section
6.1(b) or (d) hereof after the Initial Period, the Period of Employment shall
expire as of the Date of Termination and the Executive shall be entitled to
monthly severance payments in the amount of Employee's current annualized salary
(excluding any bonus or other compensation) as of the Date of Termination,
divided by twelve (12), for a period of six (6) months.

     (c)    To the extent permitted under the Company's then-current medical,
dental, disability and life insurance benefit plans, in the event that
Executive's employment is terminated

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under Section 6.1(b) or (d) during or after the Initial Period, (i) the
Executive shall also be entitled to continue to participate in such plans that
the Executive participated in prior to such termination at the same cost, if
any, that was required to be paid by the Executive for such benefits prior to
such termination, and (ii) the Executive shall be permitted to participate in
such plans for the same number of months that he would be due monthly severance
payments under Section 7.1(b) or (c), as applicable, or until the Executive is
able to replace such benefits with reasonably comparable benefits as a result of
subsequent employment, whichever is earlier.

     (e)    In the event of termination upon Disability pursuant to Section
6.1(b), any cash compensation payable to the Executive pursuant to this Section
7.1 shall be reduced by any amounts payable to the Executive as disability
benefits under any Company sponsored plan, social security or otherwise.

     7.2    RELEASE AND SATISFACTION. With respect to the Executive, his heirs,
successors and assigns, payment by the Company of the amounts and benefits
provided under this Agreement shall release, relinquish and forever discharge
the Company and any director, officer, employee, shareholder or agent of the
Company from any and all claims, damages, losses, costs, expenses, liabilities
or obligations, whether known or unknown (other than any such claims, damages,
losses, costs, expenses, liabilities or obligations (i) covered by any
indemnification arrangement of the Company with respect to the Executive, or
(ii) arising under any written employee benefit plan or arrangement (whether or
not tax-qualified) covering the Executive), which the Executive has incurred or
suffered or may incur or suffer as a result of the Executive's employment by the
Company or the termination of such employment.

     7.3    EFFECT ON THIS AGREEMENT. Any termination of the Executive's
employment and any expiration of the Period of Employment under this Agreement
shall not affect the continuing operation and effect of Section 7.2 above, which
shall continue in full force and effect with respect to the Company and the
Executive, and its and his heirs, successors and assigns.

     8.     PROPRIETARY INFORMATION, INVENTIONS AND NON-COMPETITION.

     8.1    ACCESS TO PROPRIETARY INFORMATION. The Executive acknowledges and
agrees that during the term of his employment with the Company he has had and
will have access to and become familiar with Proprietary Information (as
hereafter defined) of the Company and its subsidiaries. The Executive agrees
that for purposes of this Section 8 that employment includes full time, part
time and consulting work performed by the Executive as employee or consultant of
the Company or any of its subsidiaries at any time. The Executive further
acknowledges and agrees that he is in a position of trust and confidence with
the Company and its subsidiaries regarding such Proprietary Information and that
it is the Executive's duty to maintain the confidentiality of such Proprietary
Information and use it only for the benefit of the Company and its subsidiaries.

     8.2    PROTECTION OF PROPRIETARY INFORMATION. Accordingly, the Executive
agrees that as an integral term of this Agreement and in consideration of his
employment, salary and any bonus or severance payment and other consideration,
the sufficiency of which is hereby acknowledged, and as a condition to receiving
any such salary, bonus or severance payments that:

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     (a)    The Executive shall not disclose, either during his employment with
the Company or any subsidiary of the Company or after termination of such
employment, for whatever reason, any Proprietary Information of the Company or
any of its subsidiaries to anyone or any entity, except in the course of his
duties on behalf of the Company and its subsidiaries, and that he will not use
such information at any time for the benefit of anyone (including, without
limitation, the Executive) or any entity other than the Company or its
subsidiaries.

     (b)    The Executive agrees that upon the termination of his employment
with the Company, for whatever reason, he will leave with or return to the
Company all documents, records, notebooks or any other repositories of
information concerning the Company or its subsidiaries, including without
limitation Proprietary Information of the Company or any of its subsidiaries,
including any copies thereof that are then or later discovered to be in the
Executive's possession, whether such were developed or prepared by the Executive
or by others. This provision shall not limit the Executive's right to retain
copies of all documents, manuals and other forms of information that pertain
directly to this Agreement or terms of compensation and benefits.

     8.3    DEFINITIONS. "PROPRIETARY INFORMATION" shall include all trade
secrets and other information of any nature and in any form which is owned by
the Company or its subsidiaries and which is not publicly available or generally
known to persons engaged in businesses similar to that of the Company or its
subsidiaries, including, but not limited to, research techniques; patents and
patent applications; inventions and improvements, whether patentable or not;
development projects; computer software and related documentation and materials;
designs, practices, processes, methods, know-how and other facts relating to the
business of the Company or its subsidiaries; practices, processes, methods,
know-how and other facts related to sales, advertising, promotions, financial
matters, customers, customer lists or customers' purchases of goods or services
from the Company or its subsidiaries; and all other secrets and information of a
confidential and proprietary nature.

     8.4    DISCLOSURE. The Executive at all times during the term of this
Agreement and for a period of one (1) year after the termination of the
Executive's employment with the Company or any of its subsidiaries (the "IP
PERIOD"), for whatever reason such termination may occur, agrees to disclose to
the Company all improvements, inventions, methods, formulae, processes,
techniques, know-how and data, whether or not patentable, made or initiated,
developed or reduced to practice or learned by the Executive, either alone or
jointly with others, during the period of the IP Period which are directly
related to or directly useful in the then current businesses of the Company or
its subsidiaries or in the businesses of the Company and its subsidiaries as
proposed during Executive's employment with the Company or any such subsidiary,
or result from tasks assigned to or otherwise undertaken by the Executive, or
result from use of premises owned, leased or contracted for by the Company (all
said improvements, inventions, methods, formulae, processes, techniques,
know-how and data shall be collectively hereinafter called "INVENTIONS"). The
parties hereto acknowledge and agree that it is a condition of the Executive's
employment with the Company that he assign all Inventions existing or conceived
by him on or prior to the date hereof to the Company and the Executive hereby
does so.

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     8.5    PROPERTY RIGHTS AND ASSIGNMENT. The Executive agrees that all
Inventions of the Executive that may come into existence or be developed through
the IP Period shall be the sole property of the Company, and the Company shall
be the sole owner of all patents and other rights in connection therewith. The
Executive hereby assigns to the Company any rights that he may have or acquire
in all Inventions. The Executive further agrees as to all Inventions to
reasonably assist the Company from time to time, at any time and in every proper
way (but at the Company's expense), to obtain and enforce patents on Inventions
in any and all jurisdictions and otherwise protect and evidence the Company's
ownership of such Inventions. To that end the Executive will execute all
documents for use in applying for and obtaining such patents on Inventions and
enforcing same, as the Company may reasonably request, together with any
assignments thereof to the Company or persons designated by it. The Executive's
obligation to assist the Company in obtaining and enforcing patents for
Inventions in any and all countries shall continue without limitation beyond the
termination of the Executive's employment, but the Company shall compensate the
Executive at a reasonable rate after such termination for time actually spent by
the Executive at the Company's request on such assistance.

     8.6    NON-COMPETITION AGREEMENT.

     (a)    The Executive agrees that during the term of this Agreement and for
a period of three (3) years after a termination with cause, or for the severance
period after any other termination hereunder (the "RESTRICTED PERIOD"), he will
not either directly or indirectly, or in any capacity (whether as a promoter,
proprietor, partner, joint venturer, employee, agent, consultant, director,
officer, manager, shareholder, except as a shareholder holding less than three
percent (3%) of a publicly traded company's issued and outstanding capital
stock, or otherwise) work for, act as a consultant to, lend money or expertise
to or own any interest in the United States in any direct competitor of the
Company or any subsidiary of the Company. The Executive further agrees that he
will not, during the Restricted Period, solicit, entice, persuade, induce or
attempt to solicit, entice, persuade or induce, either directly or indirectly,
any employee, client or customer of the Company or any subsidiary of the Company
to terminate, alter or refrain from extending or renewing any contractual or
other relationship of such employee, client or customer with the Company or any
such subsidiary or, where such a relationship with the Company or any subsidiary
of the Company is one of an exclusive nature, to commence a similar or
substantially similar relationship with, any of his affiliates or any direct
competitor of the Company or any subsidiary of the Company. The Executive
further agrees that he will not cooperate with or assist, either directly or
indirectly, any person or entity engaged in any of the actions prohibited under
this Section 8.6.

     (b)    The Executive acknowledges that a breach of this Section 8.6 hereof
would cause irreparable damage to the Company, and in the event of any actual or
threatened breach of the provisions of this Section 8.6, the Company shall be
entitled, upon presentation of reasonable proof of such actual or threatened
breach, to a temporary restraining order and an injunction restraining the
Executive from breaching such covenants without the necessity of posting bond or
proving irreparable harm, such being conclusively admitted by the Executive.
Nothing shall be construed as prohibiting the Company from pursuing any other
available remedies for such breach or threatened breach, including the recovery
of damages from the Executive. The Executive agrees that issuance of an
injunction will not pose an unreasonable restriction on the

                                        7
<Page>

Executive. The parties to this Agreement agree that the limitations contained in
this Section 8.6 with respect to time, geographic area and scope of activity to
be restrained are reasonable and do not improve a greater restraint than is
necessary to protect the goodwill and other business interests of the Company.
However, if any court shall determine that the time, geographic area or scope of
activity to be restrained of any restriction contained in this Section 8.6 is
unenforceable, it is the intention of the parties hereto that such restrictive
covenant set forth herein shall not thereby be terminated but shall be deemed
amended to the extent required to render it valid and enforceable.

     (c)    If the Executive violates any covenant contained in this Section 8.6
and the Company brings any action for injunctive or other relief, the Company
shall not, as a result of the time involved in obtaining the relief, be deprived
of the benefit of the full period of any such covenant. Accordingly, the
covenants of the Executive contained in this Section 8.6 shall be deemed to have
duration as specified above, which periods shall be extended as to the Executive
for the amount of time of the violation of any such covenant by the Executive
through the date of a final judgment enforcing such covenants of the Executive.

     9.     MISCELLANEOUS.

     9.l    OTHER CONTRACTS. The Executive represents and warrants to the
Company that he is not now under any obligation of a contractual or other nature
to any person, firm, or corporation which is inconsistent or in conflict with
this Agreement or the Option Agreement, or which would prevent, limit, or impair
in any way the performance by him of his obligations hereunder.

     9.2    NOTICE. Any notice required or permitted to be given hereunder shall
be deemed sufficiently given if either hand delivered or sent by registered or
certified mail, postage prepaid, addressed to the addressee at his or its
address last provided the sender in writing by the addressee for purposes of
receiving notices hereunder or, unless or until such address shall be so
furnished, to the address indicated opposite his or its signature to this
Agreement.

     9.3    MODIFICATION AND NO WAIVER OF BREACH. No amendment, or modification
of this Agreement shall be binding unless it is in writing signed by the parties
hereto. No waiver of any provision of or obligation or breach under this
Agreement shall be binding unless it is in writing and signed by the party
against which enforcement of such waiver is sought. No such waiver of an
obligation or breach under this Agreement shall be deemed to constitute a waiver
of a future obligation or breach, whether of a similar or dissimilar nature,
except to the extent specifically provided in any written waiver under this
Section 9.3. The parties hereto acknowledge and agree that certain waivers,
amendments or modifications of this Agreement shall be conditioned on the
approval of the holders of a majority of the Series B Preferred Stock
outstanding from time to time.

     9.4    GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS.

                                        8
<Page>

     9.5    COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, but all of which taken
together shall constitute one and the same agreement.

     9.6    CAPTIONS. The captions used herein are for ease of reference only
and shall not define or limit the provisions hereof.

     9.7    ENTIRE AGREEMENT. This Agreement and the Option Agreement constitute
the entire agreement between the parties hereto relating to the matters
encompassed hereby and supersedes any prior oral or written agreements. No
amounts are owed to Executive by the Company or any of its subsidiaries under
any previous employment, consulting or similar agreements as of the date hereof.
Each of the parties expressly agrees and acknowledges that, other than those
statements expressly set forth in this Agreement, it is not relying on any
statement, whether oral or written, of any person or entity with respect to its
entry into this Agreement or to the consummation of the transactions
contemplated by this Agreement, and no representations, oral or written,
modifying or contradicting the terms of this Agreement have been made by any
party.

     9.8    ASSIGNMENT. The rights of the Executive and the Company under this
Agreement may not, without the consent of the other party hereto, be assigned,
except that the Company may assign the entirety of this Agreement to any person,
firm, corporation, or other business entity which at any time, whether by
purchase, merger, or otherwise, directly or indirectly, acquires all or
substantially all of the stock, assets or business of the Company.

     9.9    NON-TRANSFERABILITY OF INTEREST. None of the rights of the Executive
to receive any form of compensation payable pursuant to this Agreement shall be
assignable or transferable except through a testamentary disposition or by the
laws of descent and distribution upon the death of the Executive. Any attempted
assignment, transfer, conveyance, or other disposition (other than as aforesaid)
of any interest in the rights of the Executive to receive any form of
compensation to be made by the Company pursuant to this Agreement shall be void.

     9.10   TAX MATTERS. The Executive acknowledges and agrees that all payments
and benefits made or provided to Executive pursuant to the terms hereof which
are required by applicable federal, state or local laws to be subject to
withholding for income taxes or otherwise shall be so subject.

     9.11   INVALID PROVISIONS. If any provision of this Agreement is held to be
illegal, invalid, or unenforceable under any present or future law, and if the
rights or obligations of the Executive or the Company under this Agreement would
not be materially and adversely affected thereby, (a) such provisions shall be
fully severable; (b) this Agreement shall be construed and enforced as if such
illegal, invalid, or unenforceable provisions had never comprised a part hereof;
(c) the remaining provisions of this Agreement shall remain in full force and
effect and shall not be affected by the illegal, invalid, or unenforceable
provision or by its severance herefrom; and (d) in lieu of such illegal,
invalid, or unenforceable provision, there shall be added automatically as a
part of this Agreement a legal, valid, and enforceable provision as similar in
terms to such illegal, invalid, or unenforceable provision as may be possible.

                                        9
<Page>

     9.12   ARBITRATION. Any controversy or claim arising out of or relating to
this Agreement, or the breach thereof, shall be settled by binding arbitration
in accordance with the Rules of the American Arbitration Association, and
judgment upon the award rendered by the arbitrator or arbitrators may be entered
in any court having jurisdiction thereover. The arbitration proceeding shall be
conducted in the City and State of the Company's principal executive office in
the United States unless otherwise agreed by the parties thereto. The arbitrator
or arbitrators shall be deemed to possess the powers to issue mandatory orders
and restraining orders in connection with such arbitration; PROVIDED, HOWEVER,
that nothing in this Section 9.12 shall be construed so as to deny the Company
the right and power to seek and obtain injunctive relief in a court of equity
for any breach or threatened breach by Executive of any of his covenants
contained herein.

     IN WITNESS WHEREOF, the undersigned have duly executed this Agreement as of
the day and year first written above.

Address for notices:                                Presby Corp.

5910 North Central Expressway                        By:
Suite 1770                                              ------------------------
Dallas, Texas 75206                                  Name:
                                                          ----------------------
                                                     Title:
                                                          ----------------------

---------------------------                          ---------------------------
                                                     Terence A. Walts
---------------------------

---------------------------

                                       10

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