LIMITED LIABILITY COMPANY AGREEMENT

                        OF HORIZON VISION CENTERS, L.L.C.
     Organized under the Delaware Limited Liability Company Act (the "Act").

                                   ARTICLE I.

                                NAME AND LOCATION

     Section 1.1.  Name. The name of this limited  liability  company is Horizon
Vision Centers, L.L.C. (the "Company").

         Section 1.2. Members.  The members of the Company upon the execution of
this Limited Liability Company Agreement (this  "Agreement") shall be Prime RVC,
Inc., a Delaware corporation  ("Prime"),  and those certain persons,  other than
Prime,  listed on Exhibit A attached hereto ("Other  Members").  For purposes of
this  Agreement,  the  "Members"  shall  include such named  members and any new
members admitted  pursuant to the terms of this Agreement,  but does not include
any person or entity who has ceased to be a member in the Company.

     Section 1.3. Principal Office. The principal office of the Company shall be
located in 1301 Capital of Texas Hwy., Suite C-300, Austin, Texas 78746-6550, or
such other location as may be selected by the Members.

     Section 1.4. Registered Agent and Address. The name of the registered agent
and the  address  of the  registered  office of the  Company as set forth in the
Certificate of Formation of the Company are:

                          The Corporation Trust Company
                          1209 Orange Street
                          Wilmington, Delaware 19801

     Section 1.5.  Other  Offices.  Other offices and other  facilities  for the
transaction of business shall be located at such places as the Managers may from
time to time determine.


                                   ARTICLE II.

                                   MEMBERSHIP

     Section 2.1. Members' Interests.  The "Membership  Interest" of each Member
is set forth on Exhibit A.

         Section 2.2.  Admission  to  Membership.  The  admission of new Members
shall be only by the vote of the Managers pursuant to Section 8.9 hereof. If new
Members are admitted,  this Agreement  shall be amended to reflect each Member's
revised Membership Interest.

     Section 2.3.  Property  Rights.  No Member shall have any right,  title, or
interest in any of the property or assets of the Company.

         Section 2.4.  Liability of Members.  No Member of the Company  shall be
personally  liable for any debts,  liabilities,  or  obligations of the Company,
including  under a  judgment  decree,  or  order of court  except  or  expressly
provided otherwise in an agreement between the Member and the Company or another
party.

         Section  2.5.  Transferability  of  Membership.   Except  as  expressly
provided in this Agreement, Membership Interests in the Company are transferable
only with the  unanimous  written  consent  of all  Members.  If such  unanimous
written consent is not obtained when required,  the transferee shall be entitled
to receive only the share of profits or other  compensation by way of income and
the return of contributions and distributions of available earnings to which the
transferor  Member otherwise would be entitled.  Notwithstanding  the foregoing,
(i) the Membership  Interests of any Member may be freely  transferred,  without
consent, to any entity that is then owned or controlled, directly or indirectly,
by  Prime  Medical  Services,  Inc.,  a  Delaware  corporation  ("PMSI")  or its
successor in interest, (ii) the Membership Interests of any Member may be freely
assigned, pledged or otherwise transferred, without consent, to secure any debt,
liability or obligation  owed to Prime by the Company,  any Member or any entity
affiliated with the Company, (iii) the Membership Interests of any Member may be
freely assigned, pledged or otherwise transferred,  without consent, in favor of
the Lender(s)  under,  or by the Lender(s) as a result of the enforcement of any
security  interest  arising  pursuant to, those certain Credit  Facilities  (the
"Credit  Facilities") of PMSI, and/or any of PMSI's  subsidiaries,  and (iv) the
pledge by Other Members of its right to receive  distributions  from the Company
in  respect  of its  Membership  Interest  shall not be deemed  to  violate  any
provision of this Agreement.

     Section  2.6  Special  Options  to Sell  or  Acquire  Remaining  Membership
Interests.

                  (a) Prohibition on Sale. Other than those permitted  transfers
specifically set forth in Section 2.5, each Other Member agrees that it will not
transfer,  assign,  pledge,  hypothecate,  or in  any  way  alienate  any of its
Membership  Interests,  or  any  interest  therein,  whether  voluntarily  or by
operation  of law,  or by gift or  otherwise,  except  in  accordance  with  the
provisions  of this Section or Section 2.7, or except  pursuant to those certain
Assignment and Security Agreements by and between Prime/BDR Acquisition, L.L.C.,
a Delaware limited  liability  company ("BDR") or one of its affiliates and each
Other Member (the "Security Agreement").  Any purported transfer in violation of
this Section or Section 2.7 shall be void and ineffectual, and shall not operate
to transfer any interest or title to the purported transferee. Each Other Member
agrees that the Company  may,  and the Company  agrees to,  issue  stop-transfer
orders,  or take any  other  necessary  action,  to  ensure  that the  foregoing
provisions of this Section and Section 2.7 are given full effect.

                  (b) Option to Sell.  Upon (i) the death,  retirement  (only if
such  Other  Member  is David P.  Bates  III and  Jane A.  Bates  (collectively,
"Bates"), or is a physician and only as defined below),  cessation of employment
with the Company (only if such Other Member is Bates),  bankruptcy,  insolvency,
disability  (only if such Other Member is Bates,  or is a physician  and only as
defined below) or  incompetency of an Other Member,  (ii) any other  involuntary
transfer of any Membership  Interest of the Company now or hereafter owned by an
Other Member, or any interest therein (including, without limitation,  transfers
of interests upon divorce or death of a spouse of an Other Member, but excluding
any transfers  governed by Section 2.7),  (iii)  relocation of an Other Member's
primary residence (other than that of Bates) outside of a two hundred (200) mile
radius of the center or facility at which such Other  Member  primarily  renders
services,  or (iv) if such  Other  Member  is a  physician  or other  practicing
licensed professional,  the performance by an Other Member, during any one-month
period,  of  greater  than  thirty  (30%)  of his or  her  professional  medical
activities  outside of a two hundred (200) mile radius of the center or facility
primarily  utilized  by such Other  Member on the date of this  Agreement;  such
Other Member's executor,  administrator,  trustee, custodian,  receiver or other
legal or personal representative (the  "Representative"),  or such Other Member,
in the case of retirement or departure,  shall give written  notice of that fact
to the Company.  In such event,  the  Representative  or such Other Member shall
have a period of sixty (60) days (the "Put  Period")  following the date of such
death,  retirement,   bankruptcy,   insolvency,   disability,   incompetency  or
relocation  of primary  residence or practice,  as the case may be, within which
time  it may  require  that  the  Company  purchase  (subject  to the  remaining
provisions of this subsection) all of such Other Member's Membership  Interests,
upon the terms and conditions  hereinafter  set forth,  by giving notice of such
election in writing to the  Company.  The Company  may, in its sole  discretion,
offer all or a portion of such Membership  Interests to the Other Members (other
than the selling Other Member), on a pro rata basis in relation to each eligible
Other  Member's  percentage  ownership of the Company,  but any agreement by the
eligible Other Members to purchase all or a portion of such Membership Interests
shall not limit the Company's  obligation to purchase  within the time frame set
forth  in this  Section.  If the  Company  has  offered  all of such  Membership
Interests to the Other Members  (other than the selling Other  Member),  and the
eligible  Other  Members have not  committed to purchase all of such  Membership
Interests within five (5) days from the date of offer,  then the Company may, in
its  sole  discretion,  offer  all  or a  portion  of the  remaining  Membership
Interests to Prime, in which event Prime must  participate in such purchase upon
the same terms and  conditions as the Company.  For purposes of this  Agreement,
(x)  "disability"  shall apply only if the Other Member is a physician and shall
mean any condition which in the reasonable  judgment of Prime, would impair such
Other  Member's  ability to materially  perform his or her routine  duties for a
period of six (6)  months or more,  (y)  "retirement"  shall  apply only if such
Other Member is a physician and shall mean the cessation of the routine practice
of  medicine  (provided  that any  physician  who  transfers  his or her  entire
practice to a licensed medical  professional  meeting the Company's then current
credentialing  program  shall not be deemed to have retired for purposes of this
subsection),  and (z) "incompetent"  shall mean a state of legal incompetence as
declared by a court of valid jurisdiction.

                  (c) Option to Buy. In the event that the option  described  in
Section 2.6(b) arises and the  Representative  or Other Member,  as the case may
be,  fails to make the  election  described  in  Section  2.6(b)  within the Put
Period,  Prime shall at all times  thereafter have the option to purchase all or
any  portion of such Other  Member's  Membership  Interests,  upon the terms and
conditions  hereinafter  set forth, by giving written notice of such election in
writing to such other Member's  Representative or such Other Member, as the case
may be. In addition,  Prime may, in its sole  discretion,  transfer its purchase
right granted under this subsection (or all or part of the Membership  Interests
acquired  pursuant to an  exercise  of its  purchase  right  granted  under this
subsection) to the Company or any of the physician Members of the Company.

                  (d) Purchase Price.  The purchase price to be paid pursuant to
this Section shall be paid in immediately  available funds at the closing of the
transfer of Membership Interests pursuant to this Section. If the parties do not
otherwise  agree  within  thirty  (30)  days of the day on which  the  option to
purchase or sell hereunder is exercised,  then Prime shall,  at its own expense,
select an appraiser to value the Membership Interests being transferred.  If the
Other Member or its  Representative  does not agree with the value determined by
the appraiser of Prime, such Other Member or its Representative  may, at its own
expense,  select  its own  appraiser  to value the  Membership  Interests  being
transferred.  If the two appraisers  cannot agree on the value of the Membership
Interests being  transferred,  the two appraisers  shall mutually select a third
appraiser to value the Membership Interests being transferred, and any valuation
determined by such third appraiser shall be final,  binding and conclusive.  The
cost of any third appraiser shall be borne by such Other Member.

                  (e)  The  closing  of any  purchase  and  sale  of  Membership
Interests  pursuant to this Section shall take place at the principal  office of
Prime or such other place  designated by Prime and the selling Other Member,  on
the  thirtieth  day (or if such  thirtieth  day is not a business  day, the next
business day following the thirtieth day) following the delivery of notice under
either  Section  2.6(b) or Section  2.6(c).  At such closing,  the selling Other
Member  shall  execute  all  documents  and take such  other  actions  as may be
reasonably  necessary  to deliver to Prime such  Membership  Interests,  and any
certificates   representing   same,  free  and  clear  of  all  liens,   claims,
encumbrances  or  restrictions  of any kind or nature  whatsoever,  except those
imposed under the applicable Security Agreement.

         Section 2.7       Right of First Refusal.
                           ----------------------

                  (a) If there is no option  outstanding  under  Section  2.6 to
sell or buy all or any  portion  of the  Membership  Interest  held by a Selling
Other Member (as  hereinafter  defined)  (except in connection  with a sale by a
physician of all of his or her practice upon  retirement),  and any Other Member
intends to voluntarily  transfer any portion of its Membership  Interests to any
person or entity other than Prime (a "Selling Other  Member"),  then the Selling
Other  Member shall give written  notice to Prime  stating (i) the  intention to
transfer such Membership  Interests,  (ii) the amount of Membership Interests to
be transferred,  (iii) the name,  business and residence address of the proposed
transferee,  (iv) the nature and amount of the consideration,  and (v) the other
terms of the proposed sale.

                  (b) Prime shall have, and may exercise  within sixty (60) days
after receipt of the notice of intent to transfer,  an option to purchase all or
any portion of the Membership  Interests  owned by the Selling Other Member,  at
the per unit  price and upon the other  terms  stated in the notice of intent to
transfer.  Prime  may  elect to  exercise  its  option  under  this  Section  by
delivering  notice  thereof to the Selling Other Member.  If Prime elects not to
purchase all or any portion of such Membership Interests prior to the expiration
of said sixty (60) day period,  the Selling  Other Member shall have thirty (30)
days to complete the sale and purchase  contemplated  in the notice of intent to
transfer,  and after such thirty (30) day period, the provisions of this Section
shall apply fully to any such Membership Interests not transferred. The purchase
price pursuant to this Section shall be paid in immediately  available  funds at
the closing of the transfer pursuant to this Section.

                  (c) Each Other Member and Prime  acknowledge and agree that it
would be impractical to exercise an option to purchase  arising pursuant to this
Section whenever the proposed  consideration to be received by the Selling Other
Member is other than cash,  cash  equivalents  or an obligation to pay cash by a
person whose credit  worthiness and financial status is such that performance of
the payment obligation would be reasonably assured. Therefore, the parties agree
that no transfer  shall be permitted and no option shall arise  pursuant to this
Section whenever the  consideration to be received from the proposed  transferee
is other than cash,  cash  equivalents  or an obligation to pay cash by a person
whose credit  worthiness  and financial  status is such that  performance of the
payment obligation would be reasonably assured.

                  (d)  The  closing  of any  purchase  and  sale  of  Membership
Interests  pursuant to this Section shall take place at the principal  office of
Prime or such other place  designated by Prime and the Selling Other Member,  on
the  thirtieth  day (or if such  thirtieth  day is not a business  day, the next
business day following the  thirtieth  day)  following the delivery of notice of
Prime's election to purchase  pursuant to Section 2.7(b).  At such closing,  the
Selling  Other Member shall execute all documents and take such other actions as
may be reasonably necessary to deliver to Prime such Membership  Interests,  and
any  certificates  representing  same,  free  and  clear of all  liens,  claims,
encumbrances  or  restrictions  of any kind or nature  whatsoever,  except those
imposed under the Security Agreement.

         Section 2.8 Legend. Any certificate or document representing a Member's
ownership of any Membership Interests, and each certificate or document that may
be issued and delivered by the Company upon transfer of such certificate,  shall
contain a legend conspicuously noted in substantially the following form:

THE INTERESTS REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AND THEY MAY NOT BE SOLD OR TRANSFERRED  EXCEPT PURSUANT
TO AN  EXEMPTION  FROM,  OR  OTHERWISE  IN A  TRANSACTION  NOT  SUBJECT  TO, THE
REGISTRATION REQUIREMENTS OF SUCH ACT.

IN  ADDITION,  INTERSTS  MAY BE  TRANSFERRED  ONLY IN  COMPLIANCE  WITH  CERTAIN
CONDITIONS SPECIFIED IN A CERTAIN STOCK PURCHASE AGREEMENT DATED EFFECTIVE AS OF
SEPTEMBER  1,  1999,  AND IN THE  LIMITED  LIABILITY  COMPANY  AGREEMENT  OF THE
COMPANY,  A  COMPLETE  AND  CORRECT  COPY OF  EACH OF  WHICH  IS  AVAILABLE  FOR
INSPECTION AT THE  PRINCIPAL  OFFICE OF THE COMPANY AND WILL BE FURNISHED TO THE
HOLDER HEREOF UPON WRITTEN REQUEST AND WITHOUT CHARGE.

         Section 2.9.  Withdrawal of Members. A Member may not withdraw from the
Company except on the unanimous consent of the remaining  Members.  The terms of
the Members  withdrawal  shall be determined by agreement  between the remaining
Members and the withdrawing Member.

                                  ARTICLE III.

                                MEMBERS' MEETINGS

         Section  3.1.  Time and Place of Meeting.  All  meetings of the Members
shall be held at such  time and at such  place  within or  without  the State of
Delaware as shall be determined by the Managers.

         Section 3.2. Annual  Meetings.  In the absence of an earlier meeting at
such  time and place as the  Managers  shall  specify,  annual  meetings  of the
Members shall be held at the principal office of the Company during the fifth or
sixth month following the conclusion of the Company's fiscal year on such a date
which is not a legal holiday or weekend, and at such time as shall be designated
by the Managers,  and if not  designated by the Managers,  then as designated by
the  President,  at which  meeting the Members may transact such business as may
properly be brought before the meeting.

         Section 3.3. Special  Meetings.  Special meetings of the Members may be
called at any time by any Member.  Business transacted at special meetings shall
be  confined  to the  purposes  stated in the  notice of the  meeting  which may
provide,  however,  for the  transaction  of other  matters  as may be  properly
brought before the special meeting.

         Section 3.4.  Notice.  Written or printed notice stating the place, day
and hour of any Members'  meeting,  and, in the case of a special  meeting,  the
purpose or purposes for which the meeting is called, shall be delivered not less
than ten (10) days nor more than sixty (60) days before the date of the meeting,
either  personally or by mail, by or at the direction of the person  calling the
meeting, to each Member entitled to vote at such meeting. If mailed, such notice
shall be deemed to be  delivered  three (3) days  after it is  deposited  in the
United States mail,  postage prepaid,  to the Member at such Member's address as
it appears on the records of the Company at the time of mailing.

         Section 3.5. Quorum. Members present in person or represented by proxy,
holding  more than fifty  percent  (50%) of the total votes which may be cast at
any meeting  shall  constitute  a quorum at all  meetings of the Members for the
transaction  of  business.  If,  however,  such  quorum  shall not be present or
represented at any meeting of the Members, the Members entitled to vote, present
in person or represented by proxy,  shall have power to adjourn the meeting from
time to time,  without notice other than  announcement  at the meeting,  until a
quorum shall be present or represented. When any adjourned meeting is reconvened
and a quorum shall be present or  represented,  any  business may be  transacted
which might have been  transacted at the meeting as originally  noticed.  Except
with respect to the matters  listed below which require the approval by at least
eighty percent (80%) of the total votes, the Members present at a duly called or
held  meeting at which a quorum is present may  continue  to do  business  until
adjournment, notwithstanding the withdrawal of enough Members to leave less than
a quorum, if any action taken (other than adjournment) is approved by at least a
majority of the votes required to constitute a quorum.

         Section  3.6.  Voting.  Members  shall  only  be  required  to  vote in
instances  or with  respect  to  matters  where  member  voting is  required  by
applicable law or to the extent expressly  contemplated in this Agreement.  With
respect to any act or  transaction  that  requires a vote by the  Members  under
applicable law, the  affirmative  vote or written consent of not less than three
(3) of the  Managers  shall  also be  required  in order to  approve  the act or
transaction,  in each  instance.  Subject  to the  foregoing,  when a quorum  is
present at any meeting, the vote of the Members,  whether present or represented
by proxy at such  meeting,  holding more than fifty  percent  (50%) of the total
votes which may be cast at any meeting  shall be the act of the Members,  unless
the vote of a  different  number is  required  by the Act,  the  Certificate  of
Formation  or this Limited  Liability  Company  Agreement.  Each Member shall be
entitled to one vote for each percentage  point  represented by their Membership
Interest.   Fractional  percentage  point  interests  shall  be  entitled  to  a
corresponding fractional vote.

         Notwithstanding  the  foregoing,  the following  acts and  transactions
shall require the affirmative  vote of not less than eighty percent (80%) of the
total votes of the Members, represented in person or by proxy:

                  (a) Unless pursuant to any contractual  agreement to which the
         Company  is a party  on the date of  adoption  of this  Agreement,  any
         issuance  of any  Membership  Interest  of the  Company  (or  rights to
         acquire Membership Interest, through conversion,  exchange, exercise of
         options or otherwise);

     (b) Unless pursuant to any contractual  agreement to which the Company is a
party on the date of this Agreement,  any redemption of any Membership  Interest
by the Company;

     (c) The sale of all or substantially all of the assets of the Company;

                  (d)      Any merger or reorganization of or by the Company;

                  (e)      Liquidation or dissolution of the Company; and

     (f) Any  amendment  to  this  Agreement  or the  Company's  Certificate  of
Formation.

         Section  3.7.  Proxy.  Every  proxy must be  executed in writing by the
Member or by his duly authorized  attorney-in-fact,  and shall be filed with the
Secretary of the Company prior to or at the time of the meeting.  No proxy shall
be  valid  after  eleven  (11)  months  from the  date of its  execution  unless
otherwise  provided  therein.  Each proxy shall be  revocable  unless  expressly
provided therein to be irrevocable and unless otherwise made irrevocable by law.

         Section  3.8.  Action  by  Written  Consent.  Any  action  required  or
permitted  to be taken at any  meeting  of the  Members  may be taken  without a
meeting if a consent in  writing,  setting  forth the action so taken,  shall be
signed by all of the Members entitled to vote with respect to the subject matter
thereof,  and such  consent  shall have the same force and effect as a unanimous
vote of Members.

         Section 3.9. Meetings by Conference Telephone.  Members may participate
in and hold  meetings  of Members by means of  conference  telephone  or similar
communications  equipment  by means of which all  persons  participating  in the
meeting  can  hear  each  other,  and  participation  in  such a  meeting  shall
constitute   presence  in  person  at  such  meeting,   except  where  a  person
participates  in the  meeting  for  the  express  purpose  of  objecting  to the
transaction  of any  business  on the ground  that the  meeting is not  lawfully
called or convened.

                                   ARTICLE IV.

                        MEMBERSHIP CAPITAL CONTRIBUTIONS

         Section  4.1.   Capital   Contributions.   Capital  Accounts  shall  be
maintained in accordance with Treasury  Regulations  1.704-1(b) and -2 and shall
be interpreted and applied in a manner consistent therewith.  The Managers shall
have the power to amend this Agreement as may be reasonably  necessary to comply
with such  regulations.  Except for each Member's  initial capital  contribution
made in connection with the formation of the Company,  no capital  contributions
shall be required of any Member without the approval of all the Members to raise
additional capital, and only then proportionately as to each Member.

         Section 4.2. Deficit Capital Account Balances.  Upon liquidation of the
Company,  no Member with a deficit balance in his Capital Account shall have any
obligation to restore such deficit  balance,  or to make any contribution to the
capital of the Company.

         Section 4.3.  Tax Matters  Partner.  The Members  shall  designate  one
Member by  majority  vote to act as the tax matters  partner  (the "TMP") of the
Company (as defined in the Code), and the TMP is hereby  authorized and required
to represent the Company,  or designate  another person or firm to represent the
Company,  (in each  case,  at the  Company's  expense)  in  connection  with all
examinations of the Company's  affairs by tax authorities,  including  resulting
administrative  and  judicial  proceedings,  and to  expend  Company  funds  for
professional services and costs associated  therewith.  The initial TMP shall be
Prime RVC,  Inc..  The Members agree to cooperate with the TMP and its designee,
if any, and to do or refrain from doing any or all things reasonably required by
the TMP or its designee,  if any, to conduct such proceedings.  The Company will
reimburse the TMP and any such designee for all expenses  incurred in connection
with its  duties  as TMP and any costs  associated  with any  administrative  or
judicial proceeding with respect to the tax liabilities of the Members.

                                   ARTICLE V.

                             DISTRIBUTION TO MEMBERS

         Section 5.1 Distributions. At the end of each calendar quarter, subject
only to the  qualifications  and limitations set forth below,  the Company shall
distribute  its available  excess  earnings to its members,  to be divided among
them in accordance with their Membership Interests.  Distributions in kind shall
be  made  on  the  basis  of  agreed  value  as   determined   by  the  Members.
Notwithstanding  the foregoing,  the Company may not make a distribution  to its
Members to the extent that, immediately after giving effect to the distribution,
all  liabilities  of the  Company,  other than  liabilities  to the Members with
respect to their  interests and  liabilities for which the recourse of creditors
is limited to specified  property of the  Company,  exceed the fair value of the
Company  assets;  except  that the fair  value of  property  that is  subject to
liability for which  recourse of creditors is limited,  shall be included in the
Company  assets only to the extent that the fair value of the  property  exceeds
that liability.

         Section 5.2 Right of Set Off. Each of the Other Members and the Company
each agrees that Prime shall have rights of offset against  distributions  to an
Other  Member in  respect of any  Membership  Interests  or any other  ownership
interest  such  Other  Member  may have in the  Company,  for any and all debts,
obligations or liabilities that such Other Member may have to Prime,  including,
without  limitation,  any liability arising out of or relating to any obligation
arising under such Other Member's or the Company's  indemnity  obligations under
those certain Stock Purchase  Agreements by and between each Other Member,  BDR,
and  Horizon  Vision  Centers,  Inc.,  a Delaware  corporation  (each,  a "Stock
Purchase  Agreement") or any Transaction  Document (as defined in the applicable
Stock Purchase Agreement).  Each Other Member hereby authorizes the Company, and
appoints  the  Company as its  attorney in fact,  to pay such offset  amounts to
Prime and to take all other actions  necessary in connection  with such payment.
The Company  agrees to promptly  remit any and all such offset  amounts to Prime
upon request.

                                   ARTICLE VI.

              ALLOCATION OF NET PROFITS AND LOSSES FOR TAX PURPOSES

         For  accounting  and income tax  purposes,  all items of income,  gain,
loss,  deduction,  and  credit of the  Company  for any  taxable  year  shall be
allocated  among the  Members in  accordance  with their  respective  Membership
Interests,  except as agreed by the Members or as may be  otherwise  required by
the Internal Revenue Code of 1986, as amended.

                                  ARTICLE VII.

                           DISSOLUTION AND WINDING UP

     Section 7.1.  Dissolution.  Notwithstanding  any  provision of the Act, the
Company shall be dissolved only upon the first of the following to occur:

     (a) Forty (40) years from the date of filing the  Certificate  of Formation
of the Company;

     (b) Written consent of all the then current Members to dissolution;

                  (c) The  bankruptcy of a Member,  unless there is at least one
         remaining Member and such Member or, if more than one remaining Member,
         all  remaining  Members agree to continue the Company and its business;
         or

     (d) The sale of all or substantially all of the assets of the Company.

         Section 7.2.  Winding Up.  Unless the Company is continued  pursuant to
Section 7.1(c) of this Article VII., in the event of dissolution of the Company,
the Managers (excluding any Manager(s) holding office pursuant to designation by
a Member subject to bankruptcy  proceedings) shall wind up the Company's affairs
as soon  as  reasonably  practicable.  On the  winding  up of the  Company,  the
Managers  shall pay and/or  transfer the assets of the Company in the  following
order:

     (a) In  discharging  liabilities  (including  loans from  Members)  and the
expenses of concluding the Company's affairs; and

     (b) The balance, if any, shall be divided between the Members in accordance
with the Members' Membership Interests.

                                  ARTICLE VIII.

                                    MANAGERS

     Section  8.1.  Selection of Managers.  Management  of the Company  shall be
vested in the  Managers.  Initially,  the Company  shall have five (5) Managers,
being Kenneth S. Shifrin  ("Shifrin"),  Brad A. Hummel ("Hummel"),  Teena Belcik
("Belcik"),  Mark R.  Mandel,  M.D.  ("Mandel"),  and  Stephen G.  Turner,  M.D.
("Turner").  A Manager shall serve as a Manager until his or her  resignation or
removal  pursuant to Section 8.2 or 8.3.  Managers  need not be residents of the
State of Delaware or Members of the Company.

         Section 8.2. Resignations.  Each Manager shall have the right to resign
at any time upon  written  notice of such  resignation  to the  Members.  Unless
otherwise  specified in such written notice,  the resignation  shall take effect
upon the  receipt  thereof,  and  acceptance  of such  resignation  shall not be
necessary to make same effective.

         Section 8.3 Voting Agreement. Each of the parties hereto agrees that it
will vote all of the  Membership  Interests  owned by it in accordance  with the
terms  of this  Section  8.3.  Any  additional  Membership  Interests  or  other
ownership  interests  of the  Company,  or the voting  rights  related  thereto,
whether presently existing or created in the future, that may be owned, held, or
subsequently  acquired  in any  manner,  legally or  beneficially,  directly  or
indirectly,  of  record  or  otherwise,  by the  parties  at any time  after the
execution of this  Agreement,  whether  issued  incident to any interest  split,
dividend, increase in capitalization,  recapitalization,  merger, consolidation,
exchange, reorganization, or other transaction, shall be subject to the terms of
this  Section  (all such  Membership  Interests  presently  held or  controlled,
together  with such  additional  interests,  the "Subject  Interests").  At each
election of Managers of the Company,  the parties and any transferee or assignee
of  any  Subject  Interests  from  the  parties  (the  "Transferee")  shall,  in
accordance  with the  procedure set forth below,  vote the Subject  Interests as
necessary  to  elect  five  (5)  persons,  designated  in  accordance  with  the
procedures  below,  as Managers of the Company.  Three (3) of the Managers  (the
"Prime  Designees")  shall be designated in writing by Prime or its  Transferee.
The remaining two (2) Managers (the "Other Member  Designees")  shall be jointly
designated in writing by the Other  Members  holding a majority of the aggregate
Membership Interests held by all Other Members. Shifrin, Hummel and Belcik shall
be the initial  Prime  Designees;  Mandel and Turner shall be the initial  Other
Member  Designees.  For purposes of this  Section,  the Prime  Designees and the
Other Member  Designees are sometimes  referred to individually as a "Designated
Manager" and  collectively  as  "Designated  Managers."  During the term of this
Agreement,  the parties shall, in accordance with the procedure set forth below,
(i) vote their  Subject  Interests  and use their  best  efforts in any event to
ensure that the number of Managers which shall constitute all of the Managers of
the Company shall remain at five (5), (ii) vote their Subject Interests in favor
of the removal of a Designated Manager if Prime or a majority in interest of the
Other Members (whichever  designated the respective Manager) instruct in writing
that such  Designated  Manager  shall be removed  from office and (iii) upon any
removal of a  Designated  Manager  pursuant  to (ii) above,  vote their  Subject
Interests  in favor of the  election  of a  replacement  Manager  designated  in
writing by Prime or a  majority  in  interest  of the Other  Members  (whichever
designated the respective Manager).  None of the parties to this Agreement shall
approve or authorize  the removal of any  Designated  Manager  unless Prime or a
majority in interest of the Other Members  (whichever  designated the respective
Manager) shall have authorized in writing such Designated  Manager's removal. To
the extent that any party or parties entitled to designate a Manager pursuant to
this Section  fail to  designate a  replacement  Designated  Manager  under this
Section,  the  position  vacated  shall  remain  vacant until such time as a new
Manager is designated and elected pursuant to the terms hereof.

         Upon delivery of any written notice designating or removing one or more
Manager  pursuant to this Section,  the parties hereto and any Transferee  shall
either (i) sign a written consent,  prepared for execution by the Members of the
Company in accordance with this  Agreement,  which consent elects or removes the
Manager(s)  designated  in writing to be elected or removed in  accordance  with
this  Section  or (ii)  at any  annual  or  special  Members  meeting  at  which
Manager(s)  are to be  elected  or  removed,  vote in favor of the  election  or
removal  of the  Manager(s)  designated  in  writing to be elected or removed in
accordance  with this Section.  If necessary to fix the total number of Managers
at five (5), the parties  hereto  shall  either (i) sign such  written  consents
prepared  for  execution by the Members of the Company in  accordance  with this
Agreement  or (ii) at any annual or special  Members  meeting,  vote in favor of
such  motions;  which  consents  or motions  propose to fix the total  number of
Manager at five (5).

                  Each of the parties  hereto agrees to take such  actions,  and
execute  such   documents,   agreements  or  instruments   (including,   without
limitation,  consents  amending this  Agreement),  as may be  necessary,  due to
changes in the law or otherwise,  to ensure that the  provisions of this Section
8.3 are given full effect.

         Section  8.4.  General  Powers.  The  business of the Company  shall be
managed by its Managers, which may, by the vote or written consent in accordance
with this  Agreement,  exercise any and all powers of the Company and do any and
all such  lawful  acts and  things  as are not by the Act,  the  Certificate  of
Formation or this Limited Liability Company Agreement directed or required to be
exercised or done by the Members, including, but not limited to, contracting for
or incurring on behalf of the Company debts,  liabilities and other obligations,
without the consent of any other person, except as otherwise provided herein.

     Section 8.5. Place of Meetings.  The Managers of the Company may hold their
meetings,  both  regular  and  special,  either  within or without  the State of
Delaware.

         Section 8.6. Annual Meetings.  The annual meeting of the Managers shall
be held without further notice  immediately  following the annual meeting of the
Members, and at the same place, unless by unanimous consent of the Managers that
such time or place shall be changed.

         Section 8.7. Regular Meetings.  Regular meetings of the Managers may be
held upon at least ten (10) days notice,  but no more  frequently than once each
month,  at such time and place as shall from time to time be  determined  by the
Managers.  No regular  meeting or any action taken thereat shall be held void or
invalid if such notice is not given to any Manager that (i) was in attendance at
a meeting of the Managers  which fixed the time,  date and place of such regular
meeting of the Managers;  or (ii) waives notice of the regular meeting; or (iii)
attends the regular meeting in person or by telephone  conference  call; or (iv)
executes a consent to action  taken at the meeting  after  having  received  the
minutes of such regular meeting.

     Section  8.8.  Special  Meetings.  Special  meetings of the Managers may be
called by any Manager on seven (7) days notice to each Manager, with such notice
to be given personally, by mail or by telecopy, telegraph or mailgram.

         Section  8.9.  Quorum and Voting.  At all  meetings of the Managers the
presence of at least a majority of the number of Managers shall be necessary and
sufficient  to  constitute a quorum for the  transaction  of  business,  and the
affirmative  vote of at least a majority of the Managers  present at any meeting
at which there is a quorum  shall be the act of the  Managers,  except as may be
otherwise specifically provided by the Act, the Certificate of Formation or this
Agreement.  If a quorum  shall not be present at any  meeting of  Managers,  the
Managers  present there may adjourn the meeting from time to time without notice
other than announcement at the meeting, until a quorum shall be present.

         Section 8.10.  Committees.  The Managers  may, by resolution  passed by
eighty percent (80%) of the Managers,  designate  committees,  each committee to
consist  of two or more  Managers  (at  least  one of  which  must be a  Manager
designee of Prime and one of which must be a Manager designee of Other Members),
which  committees  shall have such power and  authority  and shall  perform such
functions as may be provided in such  resolution.  Such  committee or committees
shall have such name or names as may be  designated  by the  Managers  and shall
keep regular  minutes of their  proceedings  and report the same to the Managers
when required.

         8.11     Expenses and Compensation.
                  -------------------------

         (a) The Managers shall be allowed and paid all reasonable and necessary
expenses  incurred in  attending  any meeting of the  Managers.  In  determining
whether  specific  items of expense are  reasonable in amount,  the Managers may
from time to time  establish  policies  as the type of airline  travel and hotel
accommodations for which reimbursement of expenses will be paid by the Company.

         (b) The Managers may fix the  compensation  of Managers for services to
the Company as Managers,  as members of a committee,  or in any other  capacity.
Provided,  however,  that  Managers  shall not  receive  compensation  for their
services  as  Managers  except as  authorized  and  approved at a meeting of the
Members  at which at  least  two-third  (2/3)  of the  total  votes  shall be in
attendance,  and only with the affirmative  vote and approval at such meeting of
at least a majority of the Members.

         Section  8.12.  Action by  Written  Consent.  Any  action  required  or
permitted  to be  taken  at any  meeting  of the  Managers  or of any  committee
designated  by the Managers may be taken  without a meeting if written  consent,
setting  forth the  action so taken,  is signed by all the  Managers  or of such
committee,  and such consent shall have the same force and effect as a unanimous
vote at a meeting.

         Section 8.13. Meetings by Conference Telephone.  Managers or members of
any committee  designated by the Managers may  participate in and hold a meeting
of the Managers or such  committee by means of  conference  telephone or similar
communications  equipment  by means of which all  persons  participating  in the
meeting  can  hear  each  other,  and  participation  in  such a  meeting  shall
constitute   presence  in  person  at  such  meeting,   except  where  a  person
participates  in the  meeting  for  the  express  purpose  of  objecting  to the
transaction  of any  business  on the ground  that the  meeting is not  lawfully
called or convened.

     Section  8.14.  Liability of Managers.  No Manager of the Company  shall be
personally  liable for any debts,  liabilities,  or  obligations of the Company,
including under a judgment, decree, or order of the court.

         Section 8.15.  Specific Power of Managers.  The Managers shall have the
authority to enter into and execute all  documents in relation to the  formation
of the Company  including,  but not limited to,  issuance of the  Certificate of
Formation and this Limited Liability Company Agreement.

                                   ARTICLE IX.

                                     NOTICES

         Section 9.1. Form of Notice.  Whenever under the provisions of the Act,
the Certificate of Formation or this Limited  Liability Company Agreement notice
is required to be given to any Manager or Member, and no provision is made as to
how such notice shall be given,  notice shall not be construed to mean  personal
notice only, but any such notice may also be given in writing,  by mail, postage
prepaid,  addressed  to such Manager or Member at such address as appears on the
books of the Company, or by telecopy, telegraph or mailgram. Any notice required
or  permitted  to be given by mail  shall be deemed  to be given  three (3) days
after it is deposited, postage prepaid, in the United States mail as aforesaid.

         Section 9.2. Waiver. Whenever any notice is required to be given to any
Manager or Member of the Company under the provision of the Act, the Certificate
of Formation or this Limited  Liability Company  Agreement,  a waiver thereof in
writing signed by the person or persons entitled to such notice,  whether signed
before or after the time stated in such waiver,  shall be deemed  equivalent  to
the giving of such notice.

                                   ARTICLE X.

                                    OFFICERS

         Any Manager may also serve as an officer of the  Company.  The Managers
may  designate  one or more persons who are not Managers of the Company to serve
as officers and may designate the titles of all officers.  The initial  officers
of the Company  shall be: Ken  Shifrin,  Chairman of the Board;  David P. Bates,
President;  Teena Belcik,  Vice President and Treasurer;  Cheryl Williams,  Vice
President,  Secretary  and  Chief  Financial  Officer;  and  Brad  Hummel,  Vice
President.  Unless otherwise provided in a resolution of the Members or Managers
the  officers of the Company  shall have the powers  designated  with respect to
such offices under the Delaware Limited Liability Company Act, and any successor
statute, as amended from time-to-time.

                                   ARTICLE XI.

                                    INDEMNITY

         Section 11.1.  Indemnification.  The Company shall indemnify any person
who was or is a party or is  threatened  to be made a party  to any  threatened,
pending or  completed  action,  suit or  proceeding,  whether  civil,  criminal,
administrative, arbitrative or investigative, any appeal in such an action, suit
or  proceeding  and any  inquiry  or  investigation  that  could lead to such an
action,  suit or proceeding  (whether or not by or in the right of the Company),
by reason of the fact that such person is or was a manager, officer, employee or
agent of the  Company or is or was  serving at the  request of the  Company as a
director,  manager, officer, partner, venturer,  proprietor,  trustee, employee,
agent or similar  functionary of another  company,  employee benefit plan, other
enterprise, or other entity, against all judgments,  penalties (including excise
and similar  taxes),  fines,  settlements  and  reasonable  expenses  (including
attorneys'  fees and court  costs)  actually and  reasonably  incurred by him in
connection with such action,  suit or proceeding to the fullest extent permitted
by any  applicable  law,  and such  indemnity  shall inure to the benefit of the
heirs,  executors and administrators of any such person so indemnified  pursuant
to this Article XI. The right to indemnification  under this Article XI shall be
a contract  right and shall not be deemed  exclusive of any other right to which
those seeking  indemnification may be entitled under any law, bylaw,  agreement,
vote of members or disinterested managers or otherwise, both as to action in his
official  capacity  and as to action in  another  capacity  while  holding  such
office.  Any repeal or amendment of this Article XI by the Managers (pursuant to
Section  8.9  hereof)  or by  changes in  applicable  law  shall,  to the extent
permitted by applicable law, be prospective only, and shall not adversely affect
the  indemnification  of any person who may be  indemnified  at the time of such
repeal or amendment.

         Section   11.2.   Indemnification   Not   Exclusive.   The   rights  of
indemnification  and reimbursement  provided for in this Article XI shall not be
deemed  exclusive  of any  other  rights  to which  any such  Manager,  officer,
employee or agent may be  entitled  under the  Certificate  of  Formation,  this
Limited  Liability  Company  Agreement,  agreement  or vote of Members,  or as a
matter of law or otherwise.

         Section  11.3.  Other  Indemnification  Clauses.   Notwithstanding  the
foregoing,   this  Article  XI  shall  not  be  construed  to   contradict   the
indemnification  provisions  of those  certain  Stock  Purchase  Agreements  and
related transaction  documents,  dated as of September 1, 1999 (the "Transaction
Documents"),  by and  between  Prime/BDR  Acquisition,  LLC, a Delaware  limited
liability  company and certain of the  shareholders  of Horizon Vision  Centers,
Inc., a Nevada  corporation,  nor any contractual  agreement between the parties
thereto.  Notwithstanding  anything  contained herein,  this Article XI shall be
ineffectual  and shall not permit or require  indemnification  for all,  or any,
losses, costs, liabilities,  claims or expenses arising, directly or indirectly,
from any action or omission  permitting or requiring  indemnification  under the
Transaction  Documents nor any other  contractual  agreement between the parties
thereto;  and in no event may any indemnity be allowed  under this  Agreement or
pursuant to any  provision of the Act for an amount paid or payable  pursuant to
the indemnification provisions of the Transaction Documents.

                                  ARTICLE XII.

                                  MISCELLANEOUS

     Section  12.1.  Fiscal  Year.  The fiscal year of the Company  shall be the
calendar year.

     Section 12.2.  Records.  At the expense of the Company,  the Managers shall
maintain  records and accounts of all  operations of the Company.  At a minimum,
the Company shall keep at its principal place of business the following records:

     (a) A  current  list  of the  name  and  last  known  mailing  address  and
Membership Interest of each Member;

     (b) A current list of the full name and  business or  residence  address of
each Manager;

                  (c) A  copy  of  the  Certificate  of  Formation  and  Limited
         Liability Company Agreement of the Company, and all amendments thereto,
         together with executed copies of any powers of attorney;

     (d) Copies of the Federal,  state, and local income tax returns and reports
for the Company's six most recent tax years; and

     (e)  Correct  and  complete  books and  records of  account of the  Company
maintained using the accrual method of accounting.

         Section 12.3. Seal. The Company may by resolution of the Managers adopt
and have a seal, and said seal may be used by causing it or a facsimile  thereof
to be  impressed  or  affixed or in any manner  reproduced.  Any  officer of the
Company shall have authority to affix the seal to any document requiring it.

     Section 12.4. Agents.  Every Manager and Officer is an agent of the Company
for the purpose of the business. The act of a Manager or Officer,  including the
execution  in the name of the Company of any  instrument  for carrying on in the
usual way the business of the Company, binds the Company.

         Section 12.5. Checks. All checks,  drafts and orders for the payment of
money,  notes  and other  evidences  of  indebtedness  issued in the name of the
Company  shall be  signed  by such  officer,  officers,  agent or  agents of the
Company  and in such  manner  as  shall  from  time to  time  be  determined  by
resolution of the Managers. In the absence of such determination by the Mangers,
such  instruments  shall  be  signed  by  the  Treasurer  or the  Secretary  and
countersigned  by the  President  or a Vice  President  of the  Company,  if the
Company has such officers.

     Section 12.6.  Deposits.  All funds of the Company shall be deposited  from
time to time to the credit of the  Company in such  banks,  trust  companies  or
other depositories as the Managers may select.

     Section 12.7. Annual  Statement.  The Managers shall present at each annual
meeting a full and clear statement of the business and condition of the Company.

         Section 12.8.  Financial  Statements.  As soon as practicable after the
end of each fiscal year of the  Company,  a balance  sheet as at the end of such
fiscal year,  and a profit and loss  statement  for the period  ended,  shall be
distributed  to the  Members,  along with such tax  information  (including  all
information  returns) as may be necessary for the  preparation of each Member of
its Federal,  state and local income tax returns.  The balance  sheet and profit
and loss statement  referred to in the previous  sentence may be as shown on the
Company's federal income tax return.

         Section 12.9. Binding Arbitration.  Any controversy between the parties
regarding  this  Agreement and any claims  arising out of this  Agreement or its
breach  shall be submitted  to  arbitration  by either  party.  The  arbitration
proceedings shall be conducted by a single arbitrator pursuant to the Commercial
Arbitration Rules of the American Arbitration Association. The arbitration shall
be conducted in Dallas,  Texas and the arbitrator  shall have the right to award
actual  damages  and  attorney  fees and costs,  but shall not have the right to
award punitive, exemplary or consequential damages against either party.

         Section 12.10. Counterparts.  This Agreement may be executed in several
counterparts,  each of  which  shall  constitute  an  original  and all of which
together  shall  constitute  one and the same  instrument.  Any party hereto may
execute this Agreement by signing any one counterpart.

                                  ARTICLE XIII.

                                   AMENDMENTS

         Section 13.1.  Amendments.  This  Agreement may be altered,  amended or
repealed and a new limited liability  company agreement may be adopted,  only in
accordance  with the  provisions  of Section 8.9,  but  otherwise at any regular
meeting or at any special meeting called for that purpose,  or by execution of a
written consent in accordance with the provisions of Section 3.8.

         Section 13.2. When Limited  Liability  Company  Agreement Silent. It is
expressly recognized that when the Limited Liability Company Agreement is silent
or in conflict with the  requirements  of the Act as to the manner of performing
any Company function, the provisions of the Act shall control.

                             Signature Page Follows


<PAGE>



S-3

049999.0999  AUSTIN 181503 v9

                                SIGNATURE PAGE TO
                       LIMITED LIABILITY COMPANY AGREEMENT

         IN WITNESS WHEREOF,  the undersigned  Members hereby adopt this Limited
Liability  Company  Agreement as the Limited  Liability Company Agreement of the
Company, effective as of the 1st day of April, 2000.

PRIME:                                         PRIME RVC, INC.


                                               By:
                                                    Printed Name:
                                                    Title:


OTHER MEMBERS:

                                                    David P. Bates III



                                                    Jane A. Bates


                                               JOHN ROBERT GRIFFIN, M.D. FAMILY
                                               REVOCABLE TRUST DATED
                                               FEBRUARY 8, 1991


                                         By:
                                            John Robert Griffin, M.D., Trustee

                                            Christian K. Kim, M.D.

                                            TRUST AGREEMENT DATED APRIL 12,
                                                   1989

                                         By:
                                            Mark R. Mandel, M.D., Trustee





                                            D. Brent Reed, M.D.



                                            Carellyn S. Reed

                                            Bradley J. Sandler, M.D.


                                            SEVERIN FAMILY TRUST


                                         By:
                                            Sanford L. Severin, M.D., Trustee


                                         STEPHEN AND ANDREA TURNER
                                              FAMILY TRUST


                                         By:
                                             Stephen G. Turner, M.D., Trustee



                                             Stephen Wilmarth, M.D.


<PAGE>




                                             Robin J. Wagner



                             MEDICAL VISION TECHNOLOGY PROFIT SHARING PLAN, FOR
                               THE BENEFIT OF STEPHEN WILMARTH, M.D.


                                        By:  ________________________________
                                             Stephen Wilmarth, M.D., Trustee





<PAGE>



A-1

049999.0999  AUSTIN 181503 v10

                                    EXHIBIT A

                               OWNERSHIP INTERESTS

           Name                                          Ownership Percentage

          Prime RVC, Inc.                                         60.00%











                   TOTAL                                         100.00%
                                                                 ========