LIMITED LIABILITY COMPANY AGREEMENT

                                       OF

                       PRIME REFRACTIVE MANAGEMENT, 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 Prime
Refractive Management, L.L.C. (the "Company").

         Section 1.2. Members. The only member of the Company upon the execution
of this Limited Liability Company  Agreement (this  "Agreement")  shall be Prime
RVC, Inc., a Delaware corporation ("Prime"). 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.  Subject to Prime's  right to
transfer its Membership Interest pursuant to Section 2.5 below, the admission of
new Members shall be only by the unanimous  vote of the Members.  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.

         Section 2.5.  Transferability of Membership.  Except as provided below,
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 to which the transferor Member otherwise would be entitled (giving
full effect to any contractual  qualifications or restrictions on the transferor
Member's right to receive  distributions from the Company).  Notwithstanding the
foregoing,  (i) the  Membership  Interests  of Prime 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,  and (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, that certain Senior
Credit Facility of PMSI.

         Section 2.6. Resignation of Members. A Member may not withdraw from the
Company except on the unanimous consent of the remaining  Members.  The terms of
the Member's  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 on the date which
is thirty  (30) days after the end of the  Company's  fiscal year if not a legal
holiday,  and if a legal holiday,  then on the next full business day following,
at 10:00 a.m.,  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.

         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 thirty (30) days before the date of the special
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 his 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.  Once a
quorum is constituted,  the Members present or represented by proxy at a meeting
may  continue  to  transact  business  until  adjournment,  notwithstanding  the
subsequent  withdrawal therefrom of such number of Members as to leave less than
a quorum.

         Section 3.6. Voting. 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  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.

         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

         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.

                                    ARTICLE V

                             DISTRIBUTION TO MEMBERS

         The Managers shall determine, in their sole discretion,  the amount and
timing of all  distributions  from the Company.  Distributions  shall be divided
among the Members in accordance with their Membership  Interests.  Distributions
in kind shall be made on the basis of agreed value as determined by the Members.
In no event may the Company make a distribution  to its Members if,  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's  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.  Except as  contemplated in
this Article V, no distributions of cash or other assets of the Company shall be
made to the Members in their capacity as owners of the Company.

                                   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 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; or

                  (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.

         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 three (3) Managers,
being Kenneth S. Shifrin,  Brad A. Hummel,  and Cheryl L. Williams.  The Members
may, by unanimous vote of all Members,  from time to time,  change the number of
Managers  of the  Company  and,  subject  to the  foregoing  provisions  of this
Section, remove or add Managers accordingly.  A Manager shall serve as a Manager
until their 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.  Removal of Managers.  Any Manager may be removed,  for or
without  cause,  though his term may not have expired,  by the vote of more than
fifty percent (50%) of the Membership Interests of the Members.

         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 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  inside or outside  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
without  notice at such time and place as shall from time to time be  determined
by the Managers.

     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 a
majority of the Managers, designate committees, each committee to consist of two
or more Managers, 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.

     Section  8.11.  Compensation  of  Managers.  The  Members  shall  have  the
authority to fix the compensation of Managers and such  compensation may include
expenses.

         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 Agreement.

                                   ARTICLE IX

                                     NOTICES

         Section 9.1. Form of Notice.  Whenever under the provisions of the Act,
the Certificate of Formation or this 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 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: Kenneth S. Shifrin, Chairman of the Board; Joe Jenkins,
M.D., President; Cheryl Williams, Vice President,  Secretary and Chief Financial
Officer; and Teena Belcik, Treasurer.  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  corporation,  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 Members of the Company
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
Agreement or vote of Members, or as a matter of law or otherwise.

                                   ARTICLE XII

                                  MISCELLANEOUS

     Section 12.1. Fiscal Year. The fiscal year of the Company shall be fixed by
resolution of the Managers.

     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  of each
Member;
                  (b)      A current list of each Member's Membership Interest;

     (c) A copy  of the  Certificate  of  Formation  and  the  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.

         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,  and,  when called for by vote of the  Members,  at any special
meeting of the Members, 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.  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 new  Agreements  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 Agreement Silent.  It is expressly  recognized that when
the  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>



043838.0012  AUSTIN 151819 v3                       S-1

                                SIGNATURE PAGE TO

                       LIMITED LIABILITY COMPANY AGREEMENT

                                       OF

                       PRIME REFRACTIVE MANAGEMENT, L.L.C.

         IN WITNESS WHEREOF,  the undersigned Member hereby adopt this Agreement
as the Agreement of the Company, effective as of the 31st day of January, 2000.

                                                     PRIME RVC, INC.


                                                     Cheryl L. Williams

                                      Vice President and Chief Financial Officer


<PAGE>


A-1

043838.0012  AUSTIN 151819 v3

                                    EXHIBIT A

                               OWNERSHIP INTERESTS

Name                                                Ownership Percentage

Prime RVC, Inc.                                             100%