LIMITED LIABILITY COMPANY AGREEMENT

                              OF CASTER ONE, 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 Caster
One, L.L.C. (the "Company").

         Section  1.2.  Members.  The  only  members  of the  Company  upon  the
execution of this Limited Liability Company Agreement (this  "Agreement")  shall
be Prime Refractive, L.L.C., a Delaware limited liability company ("Prime"), and
Caster Eye Center Medical Group, a California professional corporation ("Caster,
Inc.").  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 Offices.  The principal offices of the Company shall
be located at 1301 Capital of Texas Hwy., Suite C-300, Austin, Texas 78746-6550,
9100 Wilshire Blvd. #265E, Beverly Hills,  California,  90212, and at such other
locations 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.

         Section 1.6  Contribution  Agreement.  The Company was initially formed
with a  single  member,  Andrew  Caster,  M.D.  ("Caster")  for the  purpose  of
consummating  the  transactions   contemplated  by  that  certain   Contribution
Agreement  dated  effective  as of March 1,  2000,  by and among  Prime  Medical
Services,  Inc., a Delaware corporation  ("PMSI"),  Prime Refractive,  L.L.C., a
Delaware limited liability company,  Caster,  Inc., Caster, and the Company (the
"Contribution  Agreement").  The parties have executed this Agreement concurrent
with the  consummation  of the  transactions  contemplated  by the  Contribution
Agreement. This agreement supercedes and replaces any prior membership agreement
or other governing or organizational document of the Company.

         Section 1.7 Certain  Defined Terms.  Unless  otherwise  defined in this
Section 1.7 of elsewhere in this Agreement,  all capitalized  terms used in this
Agreement  shall  have  the  meanings  ascribed  to  them  in  the  Contribution
Agreement.  The following terms used in this Agreement  shall (unless  expressly
provided  herein or unless the context  otherwise  requires)  have the following
respective meanings:

                  "Adjusted Capital Account Deficit" shall mean, with respect to
         any Member, the deficit balance,  if any, in a Member's Capital Account
         as of the end of the  Company's  fiscal  year,  after  giving  economic
         effect to the following adjustments: (i) credit to such Capital Account
         for any amounts which a Member is obligated to restore  pursuant to any
         provision  of this  Agreement  or is deemed to be  obligated to restore
         pursuant  to the  provisions  of  Regulations  ss.ss.1.704-2(g)(1)  and
         1.704-2(i)(5)  and (ii)  debit to such  Capital  Account  for the items
         enumerated  in   Regulations   ss.ss.1.704-1(b)(2)(ii)(d)(4)-(6).   The
         foregoing  definition of "Adjusted Capital Account Deficit" is intended
         to comply with the  provisions of  Regulations  ss.1.704-1(b)(2)(ii)(d)
         and shall be construed as being consistent therewith.

                  "Capital Account" shall mean, with respect to each Member, the
         capital  account which is maintained as part of the Company's books and
         records, in accordance with the following:

                           (i) Each  Member's  Capital  Account will be credited
                  with the  amount of money  contributed  by such  Member to the
                  capital of the Company,  plus the initial Gross Asset Value of
                  any property (other than money)  contributed by such Member to
                  the capital of the Company (net of  liabilities  securing such
                  contributed  property that the Company is considered to assume
                  or take  subject  to under  Section  752 of the Code) plus the
                  amount of any Net Income  allocated  to such  Member,  and the
                  amount of any items in the nature of income or gain  specially
                  allocated to such Member pursuant to Sections 6.3 or 6.4;

                           (ii) Each Member's Capital Account will be debited by
                  the amount of money  distributed to such Member by the Company
                  (exclusive  of a  guaranteed  payment  within  the  meaning of
                  ss.707(c)  of the Code  paid to such  Member),  plus the Gross
                  Asset Value of any property  distributed to such Member by the
                  Company (net of liabilities securing such distributed property
                  that such Member is  considered  to assume or take  subject to
                  under ss.752 of the Code) and decreased  further by the amount
                  of any Net Loss allocated to such Member and the amount of any
                  items in the nature of loss or deduction  specially  allocated
                  to such Member pursuant to Sections 6.3 or 6.4.

                           (iii) The Capital  Account of a Member who receives a
                  distribution  in liquidation  of his Membership  Interest that
                  gives  rise to an  adjustment  to the  adjusted  tax  basis of
                  Company  property  under  ss.734  of  the  Code  shall  have a
                  corresponding adjustment made to such Member's Capital Account
                  in accordance with the provisions of Regulation ss.1.704-1(b).
                  In  the  event  of  any  other  Distribution  (as  hereinafter
                  defined)  to a Member that gives rise to an  adjustment  under
                  Code ss.  734,  an  adjustment  shall  be made to the  Capital
                  Accounts of all of the Members in accordance  with  Regulation
                  ss. 1.704-1(b)(iv)(m)(4).

                           (iv) In the event the Gross  Asset  Value of  Company
                  assets are adjusted  pursuant to the terms of this  Agreement,
                  the  Capital   Accounts  of  the  Members  shall  be  adjusted
                  simultaneously  to reflect the aggregate net  adjustment as if
                  the  Company  recognized  gain or loss  equal to the amount of
                  such  aggregate  net  adjustment  and  such  gain or loss  was
                  allocated   to  the  Members   pursuant  to  the   appropriate
                  provisions of this Agreement.

                           (v) The foregoing Capital Account  definition and the
                  other provisions of this Agreement relating to the maintenance
                  of Capital  Accounts are  intended to comply with  Regulations
                  ss.1.704-1(b)(2)(iv),  and shall be interpreted and applied in
                  a manner consistent with such Regulations,  with such optional
                  adjustments  as the Managers  shall  determine  appropriate in
                  order to provide that the Company's allocations shall meet the
                  "substantial   economic   effect"   test  of  the   applicable
                  Regulations.

                  "Company Minimum Gain" shall have the same meaning as ascribed
         to the term " partnership minimum gain" set forth in Regulations ss.ss.
         1.704-2(b)(2) and 1.704-2(d).

                  "Distribution"  shall mean money or property  distributed to a
         Member in its capacity as a Member pursuant to Article V hereof.

                  "Gross  Asset Value"  means,  with respect to any asset of the
         Company,  the asset's  adjusted  basis for federal income tax purposes;
         provided,  however,  that  (a)  the  Gross  Asset  Value  of any  asset
         contributed  by a Member to the Company or  distributed  to a Member by
         the Company shall be the gross fair market value of such asset (without
         taking into account  ss.7701(g) of the Code), as reasonably  determined
         by the contributing or distributee  Member, as the case may be, and the
         Company or in the case of assets initially  contributed the amounts set
         forth on Schedule A, (b) the Gross Asset  Values of all Company  assets
         shall be adjusted to equal their  respective  gross fair market  values
         (taking into account ss.7701(g) of the Code), as reasonably  determined
         by the Managers upon the  termination of the Company for federal income
         tax purposes pursuant to ss.708(b) of the Code; and (c) the Gross Asset
         Values of all Company  assets may be adjusted in the  discretion of the
         Managers to equal their respective gross fair market value (taking into
         account  ss.7701(g)  of the  Code),  as  reasonably  determined  by the
         Managers  as of (i)  the  date  of  the  acquisition  of an  additional
         interest in the Company by any new or existing  Member in exchange  for
         more than a de minimis contribution to the capital of the Company; (ii)
         upon the distribution by the Company to a retiring or continuing Member
         of more  than a de  minimis  amount  of  Company  property  or money in
         reduction of such Member's  interest in the Company;  or (iii) upon the
         liquidation   of  the  Company   within  the  meaning  of   Regulations
         ss.1.704-1(b)(2)(ii)(g);  provided,  however, that the adjustments made
         pursuant  to clauses  "(i)" and "(ii)"  above shall be made only if the
         Managers  reasonably  determine that such  adjustments are necessary or
         appropriate to reflect the relative  economic  interests of the Members
         in the Company.

                  "Member  Minimum Gain" shall mean an amount,  determined  with
         respect to each Member  Non-Recourse Debt, equal to the Company Minimum
         Gain that would result if such Member Non-Recourse Debt were treated as
         a Non-Recourse  Liability,  determined in accordance  with  Regulations
         ss.1.704-2(i)(3).

                  "Member  Non-Recourse  Debt"  shall  have the same  meaning as
         ascribed  to  the  term  "partnership  nonrecourse  gain"  pursuant  to
         Regulations ss.1.704-2(i)(5).

                  "Member  Non-Recourse  Deductions" shall have the same meaning
         as ascribed to the term "partner  nonrecourse  deductions"  pursuant to
         Regulations   ss.1.704-2(i)(2).   The  amount  of  Member  Non-Recourse
         Deductions with respect to a Member  Non-Recourse Debt during a Company
         taxable year shall equal the excess,  if any, of the net  increase,  if
         any,  in the amount of Member  Minimum  Gain  attributable  to a Member
         Non-Recourse  Debt during that taxable year, over the aggregate  amount
         of any  Distributions  during that taxable year to the Member who bears
         the economic  risk of loss for such Member  Non-Recourse  Debt,  to the
         extent  that such  Distributions  are from the  proceeds of such Member
         Non-Recourse  Debt and are  allocable to an increase in Member  Minimum
         Gain  attributable  to such Member  Non-Recourse  Debt,  determined  in
         accordance with the Regulations ss.1.704-2(i)(2).

                  "Net  Income" or "Net Loss" shall mean the  taxable  income or
         gain and taxable loss as determined in accordance  with the  accounting
         methods  followed  by the  Company  for  federal  income tax  purposes,
         pursuant to Code ss.703(a) (and for purposes of determining  Net Income
         or Net Loss, all items of income,  gain, loss or deduction  required to
         be stated separately pursuant to Code ss.703(a)(1) shall be included in
         Net Income or Net Loss) subject to the following adjustments:

                           (i) Any Company  income  that is exempt from  federal
                  tax, and not  otherwise  taken into  account in computing  Net
                  Income or Net Loss,  shall be added to such taxable  income or
                  loss;

                           (ii) Any Company  expenditures which are described in
                  Code  ss.705(a)(2)(B)  (or  deemed  to  be  such  expenditures
                  pursuant to  Regulations  ss.1.704-1(b)(2)(iv)(i)(1))  and not
                  otherwise  taken into account in  computing  Net Income or Net
                  Loss pursuant to this definition shall be subtracted from such
                  taxable income or loss;

                           (iii) Any deductions for depreciation,  cost recovery
                  or  amortization  attributable  to any  assets of the  Company
                  shall be  determined  by reference to their Gross Asset Value,
                  except that if the Gross Asset Value of an asset  differs from
                  its adjusted tax basis for federal  income tax purposes at any
                  time  during such year or other  period,  the  deductions  for
                  depreciation,  cost recovery or  amortization  attributable to
                  such asset from and after the date  during such year or period
                  in which  such  difference  first  occurs  shall bear the same
                  ratio to the Gross  Asset Value as of such date as the federal
                  income tax  depreciation,  amortization or other cost recovery
                  deduction  for such year or other  period  from and after such
                  date  bears  to  the  adjusted  tax  basis  as of  such  date;
                  provided,  however,  that if the  adjusted  basis for  federal
                  income  tax  purposes  of an  asset at the  beginning  of such
                  fiscal year is zero,  such deductions for  depreciation,  cost
                  recovery,  or amortization  shall be determined with reference
                  to such  beginning  Gross  Asset  Value  using any  reasonable
                  method selected by the Managers.

                           (iv) Gain or loss, resulting from the Company taxable
                  disposition of any Company property with respect to which gain
                  or loss is recognized for federal  income tax purposes,  shall
                  be  computed  by  reference  to the Gross  Asset  Value of the
                  disposed property,  notwithstanding the fact that the adjusted
                  tax bases of such  property  may differ  from its Gross  Asset
                  Value; and

                           (v) Any items of income or loss  which are  specially
                  allocated  pursuant to Sections 6.3 and 6.4 shall not be taken
                  into  account in  computing  the  Company's  Net Income or Net
                  Loss.

                  "Non-Recourse  Deductions" shall have the meaning  established
         by  Regulations   ss.1.704-2(b)(1).   The  aggregate  of   Non-Recourse
         Deductions  for a taxable year of the Company shall equal the excess of
         the net increase, if any, in the amount of Company Minimum Gain, during
         that taxable year over the  aggregate  amount of  Distributions  during
         that taxable  year of proceeds of a  Non-Recourse  Liability  which are
         allocable to an increase in Company Minimum Gain,  determined  pursuant
         to Regulations ss.1.704-2(d).

                  "Non-Recourse Liability" shall have the meaning established by
Regulations ss.1.704-2(b)(3).

                                   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.  Nothing contained in this
Section 2.4 shall be construed  to limit the  liability of Members to each other
or the Company under the terms of any provision of the Contribution Agreement or
other Transaction Documents.

         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.
Notwithstanding the foregoing,  the following shall not be deemed to violate any
provision of this Agreement (each, a "Permitted  Transfer"):  (i) the Membership
Interests of Prime may be freely  transferred,  without  consent,  to any entity
that is then  owned and  controlled,  directly  or  indirectly,  by 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,
(iv) the pledge by Caster,  Inc.  (pursuant to Section 10.2 of the  Contribution
Agreement) of its right to receive  distributions from the Company in respect of
its Membership Interest, and (v) the Membership Interests of Caster, Inc. may be
transferred  (A) to a trust or trusts (a  "Permitted  Trust") for the benefit of
Caster and/or members of Caster's immediate family (including an entity owned by
a Permitted  Trust) but only where Caster  either  controls the trust or retains
during his  lifetime  the  exclusive  ability to vote the  Membership  Interests
(pursuant to a written proxy or other instrument  reasonably  acceptable in form
and  substance  to  Prime),  (B) to an entity  (a  "Permitted  Entity")  that is
wholly-owned,  directly  or  indirectly,  by Caster  and/or  members of Caster's
immediate  family,  but only where Caster either  controls the entity or retains
during his  lifetime  the  exclusive  ability to vote the  Membership  Interests
(pursuant to a written proxy or other instrument  reasonably  acceptable in form
and substance to Prime),  or (C) from a Permitted  Trust or Permitted  Entity to
Caster.  Notwithstanding the foregoing, after the expiration of the six (6) year
period  immediately  following  the Closing Date (as such term is defined in the
Contribution  Agreement),  Caster,  Inc.  shall be  entitled  to sell all or any
portion of its Membership  Interest and Caster may sell or cause Caster, Inc. to
sell, any portion of the Stock Interest (as hereinafter  defined) to one or more
ophthalmologists that are primarily engaged in Refractive Surgery and reasonably
acceptable to Prime;  provided,  however, that Prime's refusal to approve of any
proposed transferee(s) as required by this sentence shall be deemed to have been
reasonable  for all purposes if such  transferee(s)  cannot  demonstrate  to the
reasonable  satisfaction of Prime that such  transferee(s)  would have generated
the same annual  level of revenue and  profitability  for the Company  following
such  transfer as did  Caster,  on  average,  for the two (2) years  immediately
preceding  such transfer (in each case  multiplied by the  percentage of Caster,
Inc.'s total Membership  Interest,  or Caster's  percentage of outstanding Stock
Interest,  as the case may be, being  conveyed).  Caster,  Inc.  represents  and
warrants  to Prime and the  Company  that all of its  ownership  interests  (the
"Stock  Interests")  are,  as of the date it enters into this  Agreement,  owned
solely by Caster. Any transfer, issuance, sale, conveyance or encumbrance of any
Stock Interests,  or any interest  therein,  by Caster or Caster,  Inc. shall be
subject to the same restrictions on transfer as are set forth above with respect
to transfers of  Membership  Interests.  Accordingly,  any transfer of any Stock
Interests in violation of these restrictions  shall, if Caster, Inc. is then the
owner of any  Membership  Interest,  be  deemed a  transfer  of  Caster,  Inc.'s
Membership Interest in violation of this Agreement.  Similarly,  any transfer of
any Stock  Interests in a transaction  described in clauses  (ii),  (iii) or (v)
above as a Permitted Transfer shall be permitted as well.

         As an  express  condition  to  any  transfer  by  Caster,  Inc.  or any
transferee  of Caster,  Inc.,  the  proposed  transferee  shall  have  agreed in
writing,  in form and  substance  reasonably  satisfactory  to Prime,  that such
proposed  transferee  will be bound by all of the terms and  provisions  of this
Agreement,  the Contribution  Agreement and any other  Transaction  Document (as
defined in the  Contribution  Agreement)  which by  reasonable  implication  are
applicable to the Membership Interest being transferred and not solely Caster or
Caster,   Inc.   as  a  selling   party   under  the   Contribution   Agreement.
Notwithstanding  any other  provisions  of this  Agreement,  if  Caster  dies or
becomes incapacitated,  or can no longer manage his affairs,  Caster's executor,
administrator,  conservator,  guardian, trustee, personal representative, or the
holder of a power of  attorney  from  Caster may  exercise  all of the rights of
Caster,  Inc. under this Agreement,  including the right to vote, to designate a
Manager,  and to receive  distributions.  In the event of  Caster's  death,  the
transfer of Stock  Interests to Caster's heirs or legatees,  whether by the laws
of  descent  and  distribution,  operation  of  law  or  otherwise,  or  to  the
beneficiaries of a Permitted Trust, shall be deemed to be a Permitted  Transfer.
By signing this Agreement in his capacity as an officer of Caster,  Inc., Caster
is also  acknowledging and agreeing to the restrictions on transfer of the Stock
Interests as provided herein.

         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.  Members  shall  only  have the right to vote in
instances or with respect to matters  where member voting or consent is required
by  applicable  law or to the  extent  expressly  set  forth in this  Agreement,
including but not limited to, Sections 2.5 (transfers of Membership  Interests),
7.1(b) (dissolution),  8.1 (changing the number of Managers), 8.11 (compensation
of  Managers)  and 13.1  (amendments  to  operating  agreement,  certificate  of
formation). With respect to any act or transaction that requires the affirmative
vote or consent by the Members under  applicable  law, the  affirmative  vote or
written  consent  of two of the three  Managers  (one of whom  must,  as long as
Caster has not delivered the written  notice  described in Section 9.3(a) of the
Contribution  Agreement,  be the Manager designee of Caster, Inc.) 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. The provisions
of this Section  shall in all events be  subordinate  to with the  provisions of
Section 8.9 relating to acts or transactions  requiring the written  approval of
two (2) or more Managers,  one of which must be a Manager  designated by Caster,
Inc.

         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 any  meeting  of  Members  by  telephone  (including  a  conference
telephone) conference telephone or similar communications  equipment by means of
which all persons  participating  in the  meeting can hear each other,  and such
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.  Each Member has contributed to the
Company  the assets set forth in  Schedule  A,  having  the agreed  fair  market
values,  as set forth on  Schedule  A, which  amount  shall be  credited to each
Member's Capital Account as their initial capital contribution.  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 unanimous approval of all the Members to raise additional capital,  and only
then proportionately as to each Member.

         Section 4.2.      Intentionally Omitted.

         Section 4.3. Deficit Capital Account Balances.  Upon liquidation of the
Company,  no Member with a deficit balance in its Capital Account shall have any
obligation to restore such deficit  balance,  or to make any contribution to the
capital of the Company.

         Section 4.4. Tax Matters  Partner.  The Managers  shall  designate  one
Manager 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
Teena Belcik.  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 of Available Excess Earnings. At the end of
each calendar  month,  subject only to the  qualifications  and  limitations set
forth below,  the Company shall,  unless  provided  otherwise in accordance with
Section 8.9(b) or Section 8.9(c),  distribute its Available  Excess Earnings (as
hereinafter defined) to its members, to be divided among them in accordance with
their Membership  Interests.  As used herein,  "Available Excess Earnings" shall
mean and refer to all cash and cash equivalents of the Company that would not be
reasonably  required in order to (a) satisfy  all  accounts  payable and payment
obligations  of the Company that will become due in the ordinary  course  within
thirty (30) days of the date of determination (assuming no receipt of additional
cash or cash  equivalents  during such ninety (30) day period) or (b)  establish
adequate reserves to satisfy  liabilities or obligations of the Company that are
foreseen  and  can  be  reasonably  estimated  on  the  date  of  determination.
Distributions  in kind shall be made on the basis of agreed value as  determined
by the  Managers.  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  Distributions to Pay Tax. In the event the  distributions,
with  respect  to any  fiscal  year,  to any Member are less than the Income Tax
Liability (as  hereinafter  defined) of such Member for that fiscal year,  then,
notwithstanding  anything to the contrary in this Agreement,  within two and one
half (2.5)  months  after the close of such fiscal year  distributions  shall be
made to the Members in proportion to their respective Membership Interests in an
aggregate amount equal to the Income Tax Liability (as hereinafter  defined). As
used in this Agreement, the "Income Tax Liability" shall mean the product of the
net  income of the  Company  for such  fiscal  year  multiplied  by the  highest
marginal rate  applicable to individuals  for federal and California  income tax
purposes,  and giving effect to any federal  income tax deduction for California
tax. If the Company may not make a distribution  pursuant to this Section 5.2 as
a result of the  application  of Section 5.1, the Company may, with the approval
of the Managers, make a loan to each Member in an amount equal to the difference
between  the amount of the  Income  Tax  Liability  determined  pursuant  to the
preceding sentence and the amount otherwise  distributed to such Member pursuant
to Sections 5.1 and 5.2.

                                   ARTICLE VI.

                      ALLOCATION OF NET PROFITS AND LOSSES

         Section 6.1.  Allocation of Net Income and Net Loss. Net Income and Net
Loss for each fiscal year shall be allocated  between the Members in  accordance
with their respective Membership Interests.

         Section 6.2.  Loss  Limitation.  Notwithstanding  Section 6.1, Net Loss
shall not be allocated to any Member to the extent such  allocation  would cause
such  Member to have an  Adjusted  Capital  Account  Deficit.  Any Net Loss that
cannot  be  allocated  to a  Member  by  virtue  of this  Section  6.2  shall be
reallocated to other Members.  If both Members have an Adjusted  Capital Account
Deficit,  the balance of the Net Loss shall be allocated  between the Members in
proportion to their Membership Interest.

     Section 6.3. Special  Allocations.  The following special allocations shall
be made in the following order:

                  (a) Company Minimum Gain Chargeback. Notwithstanding any other
provision of this Article 6, if there is a net decrease in Company  Minimum Gain
during any fiscal  year,  each  Member  shall be  specially  allocated  items of
Company income and gain for such year (and, if necessary,  subsequent  years) in
proportion  to, and to the extent of, an amount equal to such Member's  share of
the  net  decease  in  Company  Minimum  Gain,  determined  in  accordance  with
ss.1.704-(2)(g)(2) of the Regulations. This Section 6.3(a) is intended to comply
with the minimum gain  chargeback  requirement of the  Regulations  and shall be
interpreted consistently therewith.

                  (b) Member Minimum Gain Chargeback.  Notwithstanding any other
provision of this Article 6 except Section 6.3(a), if there is a net decrease in
Member Minimum Gain attributable to a Member  Nonrecourse Debt during any fiscal
year,  each Member with a share of the Member Minimum Gain  attributable to such
Member Nonrecourse Debt,  determined in accordance with  ss.1.704-2(i)(5) of the
Regulations,  shall be specially  allocated items of Company income and gain for
such year (and, if  necessary,  subsequent  years) in proportion  to, and to the
extent of, an amount equal to such  Member's  share of the net decease in Member
Minimum  Gain  attributable  to such  Member  Nonrecourse  Debt,  determined  in
accordance  with  ss.1.704-2(i)(5)  of the  Regulations.  This Section 6.3(b) is
intended to comply with the Member  minimum gain  chargeback  requirement of the
Regulations and shall be interpreted consistently therewith.

                  (c)  Qualified   Income  Offset.   In  the  event  any  Member
unexpectedly receives any adjustments, allocations or distributions described in
ss.ss.1.704-1(b)(2)(ii)(d)(4),  (5) and (6) of the Regulations, items of Company
income and gain shall be  specially  allocated  to each such Member in an amount
and manner  sufficient to eliminate,  to the extent required by the Regulations,
the  Adjusted  Capital  Account  Deficit of such Member as quickly as  possible,
provided that an allocation  pursuant to this Section  6.3(c) shall be made only
if and to the extent that such Member  would have an  Adjusted  Capital  Account
Deficit  after all other  allocations  provided  for in this Article 6 have been
tentatively made as if this Section 6.3(c) were not in the Agreement.

     (d) Nonrecourse Deductions.  Any Nonrecourse Deductions for any fiscal year
or other period shall be specially  allocated among the Members in proportion to
their Membership Interests.

                  (e) Member  Nonrecourse  Deductions.  Any  Member  Nonrecourse
Deductions  for any fiscal year or other period shall be allocated to the Member
who bears the economic risk of loss with respect to the Member  Nonrecourse Debt
to which such Member Nonrecourse  Deductions are attributable in accordance with
Regulations ss.1.704-2(i).

         Section 6.4 Curative Allocations.  The "Regulatory Allocations" consist
of the  allocations  to a Member (or its  predecessor)  under  Sections  6.3(a),
6.3(b),  6.3(c), 6.3(d) and 6.3(e) hereof.  Notwithstanding any other provisions
of this  Article  6 (other  than the  Regulatory  Allocations),  the  Regulatory
Allocations  shall be taken into  account in  allocating  other items of income,
gain, loss and deduction among the Members so that, to the extent possible,  the
net amount of such allocations of other items and the Regulatory  Allocations to
each Member  shall be equal to the net amount that would have been  allocated to
each such Member if the Regulatory Allocations had not occurred. For purposes of
applying the foregoing sentence (i) no allocations  pursuant to this Section 6.4
with respect to  allocations  pursuant to Section  6.3(a) shall be made prior to
the fiscal year during  which there is a net decrease in Company  Minimum  Gain,
and  then  only  to  the  extent  necessary  to  avoid  any  potential  economic
distortions  caused  by such  net  decease  in  Company  Minimum  Gain,  (ii) no
allocations  pursuant  to this  Section  6.4  shall  be  made  with  respect  to
allocations  pursuant to  Sections  6.3(b) and 6.3(e)  relating to a  particular
Member  Nonrecourse  Debt prior to the fiscal year  during  which there is a net
decrease in Member Minimum Gain  attributable to such Member  Nonrecourse  Debt,
and  then  only  to  the  extent  necessary  to  avoid  any  potential  economic
distortions  used  by such  net  decease  in  Member  Minimum  Gain,  and  (iii)
allocations  pursuant  to this  Section 6.4 shall be  deferred  with  respect to
allocations  pursuant to Section 6.3(e) hereof  relating to a particular  Member
Nonrecourse  Debt to the  extent the  Managers  reasonably  determine  that such
allocations  are  likely to be  offset by  subsequent  allocations  pursuant  to
Section  6.3(b)  hereof.  The Managers shall have  reasonable  discretion,  with
respect to each fiscal year, to (i) apply the  provisions of this Section 6.4 in
whatever  order is  likely to  minimize  the  economic  distortions  that  might
otherwise  result  from  the  Regulatory   Allocations,   and  (ii)  divide  all
allocations  pursuant to this  Section 6.4 among the Members in a manner that is
likely to minimize such economic distortions.

         Section 6.5 Tax  Allocations;  Code ss.704(c).  In accordance with Code
ss.704(c) and the Regulations thereunder, income, gain, loss, and deduction with
respect to any property  contributed  to the capital of Company,  or any Company
asset which is subject to adjustment in its Gross Asset Value, any such property
or asset of the Company shall,  solely for tax purposes,  be allocated among the
Members so as to take account of any  variation  between the  adjusted  basis of
such  property or asset to the Company for federal  income tax  purposes and its
Gross Asset Value. Any elections or other decisions relating to such allocations
shall be made by the Managers in any manner that reasonably  reflects the intent
of this  Agreement.  Allocations  pursuant  to this  Section  6.5 are solely for
purposes of federal,  state, and local taxes and shall not affect, or in any way
be taken into account in computing, any person's Capital Account or share of Net
Income,  Net Loss,  other items, or  Distributions  pursuant to any provision of
this Agreement.

                                  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; or

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

         Section 7.2.  Winding Up. In the event of  dissolution  of the Company,
the Managers  (excluding any Manager 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 distributed to the Members
         in  accordance  with  the  positive  balances  of the  Members  Capital
         Accounts. Upon dissolution and distribution of the Company assets, such
         distributed  assets shall be deemed sold with the  resulting Net Income
         or Net Loss being  allocated  among the Members and credited or debited
         to their respective Capital Accounts pursuant to Articles IV and VI.

                                  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 Brad Hummel and Teena Belcik (as the initial Manager  designees of Prime),
and Andrew  Caster,  M.D.  (as the initial  Manager  designee of Caster,  Inc.).
Thereafter,  for so long as there  are three (3)  Managers,  (a) Prime  shall be
entitled to designate two (2) of the  Managers;  and (b) Caster,  Inc.  shall be
entitled  to  designate  the  remaining  one (1)  Manager.  Notwithstanding  the
foregoing,  a Member shall not be entitled to designate  any Manager  unless its
Membership  Interest:  (y) has not (other than as allowed  under  Section 2.5 of
this Agreement) been transferred,  repurchased,  assigned, pledged, hypothecated
or in any way  alienated;  and (z) equals or exceeds thirty percent (30%) of the
aggregate  Membership  Interests  (after  including  in such  determination  all
Membership  Interests  held  by  the  permitted  transferees  of  such  Member);
provided,  however,  that the foregoing limitations shall not apply in the event
the parties  restructure  their  relationship  pursuant to this  Agreement in an
effort to comply with any  applicable  law, rule or  regulation  that makes such
restructuring necessary. The Members may, by unanimous vote of all Members, from
time to time,  change the number of  Managers  of the  Company and remove or add
Managers  accordingly.  A  Manager  shall  serve as a  Manager  until his or her
resignation  or removal  pursuant  to Section 8.2 or 8.3 of this  Article  VIII.
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.  The Member who designated a resigning manager
shall be entitled to designate the successor  thereto without any further action
by the Members or other Managers. If any action of the Members is required under
applicable  law,  the Members  agree to take such action and any other action as
may be necessary  from time to time to effectuate the provisions of this Section
8.2.

         Section 8.3.  Removal of Managers.  Any Manager may be removed,  for or
without cause,  at any time, but only by the Member who designated such Manager,
upon the written notice to all Members.  The Member who designated  such removed
Manager shall be entitled to designate the successor  without any further action
by the Members or other Managers. If any action of the Members is required under
applicable  law,  the Members  agree to take such action and any other action as
may be necessary  from time to time to effectuate the provisions of this Section
8.3.

         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, and any Manager shall be entitled to attend any meeting by telephone.

         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 written notice at such time and place as shall from time to time be
determined  by the  Managers.  As long as Caster has not  delivered  the written
notice described in Section 9.3(a) of the Contribution  Agreement, no meeting of
the Managers  shall be held without the Manager  designee of Caster,  Inc. being
given at least seven (7) days prior notice.

     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.
                           -----------------

                  (a) At all  meetings of the  Managers the presence of at least
         two (2) 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 Contribution Agreement,
         the Certificate of Formation,  this Limited Liability Company Agreement
         or any other Transaction  Document. 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.

                  (b) In  addition  to the  other  provision  contained  in this
         Agreement requiring the unanimous vote of the Members or the consent of
         Caster,  Inc. or Caster,  Inc.'s designated  Manager, as long as Caster
         has not died or become permanently  disabled,  and no Trigger Event (as
         defined  in  the  Contribution  Agreement)  has  occurred  (subject  to
         Caster's right to withdraw any Termination  Notice), the following acts
         or transactions by, or involving,  the Company may not be taken without
         first obtaining the written consent of (A) Caster,  Inc., any person to
         whom Caster, Inc.'s Membership Interest has been rightfully transferred
         pursuant to the Section 2.5, or the Manager  designee of Caster,  Inc.,
         and (B) Prime, any person to whom Prime's Membership  Interest has been
         rightfully  transferred pursuant to the Section 2.5, or each of the two
         (2) Manager  designees  of Prime;  provided,  however,  that no written
         consent  of any  party is  required  under  this  subsection  to take a
         particular  action  if (but only to the  extent  that)  such  action is
         required to be taken  pursuant to the express  terms and  provisions of
         the Contribution Agreement:

                           i. Disposition, sale, assignment or other transfer by
                  the  Company of any  interest it owns in the  Company,  except
                  that such  interest may be  extinguished  without the approval
                  required under this Article.

     ii. The election or removal of officers,  and  establishing or changing the
compensation for officers or other employees in a manner  inconsistent with past
practices.

     iii.  Initiating or settling any  litigation or regulatory  proceeding,  or
confessing any judgment.

     iv. Hiring or changing the Company's accountants or legal counsel.

     v. Opening or closing bank or other depository  accounts,  and establishing
or  changing  the  signature  withdrawal  authority  with  respect  to any  such
accounts.

     vi.  Waiving,  refusing to enforce,  amending,  restating,  superseding  or
modifying any of the provisions of this Agreement or any Transaction Document.

                           vii.  Entering into or  terminating  agreements  with
                  medical  doctors with respect to the performance of procedures
                  in the Company's  facilities relating to Refractive Surgery or
                  otherwise.

     viii. Moving the location of the Company's principal place of business.

                           ix. Amending,  modifying,  canceling,  extending,  or
                  renewing the Facility Use Agreement or any other  agreement to
                  which  the  Company  is  a  party  and  relating  to  Caster's
                  performance of medical services,  the Business,  or Refractive
                  Surgery, or the Company's entering into, amending,  modifying,
                  canceling,  extending or renewing any other similar  agreement
                  with any other person,  firm,  or entity  relating to Caster's
                  performance of medical services,  the Business,  or Refractive
                  Surgery Caster.

     x.  Mergers,  consolidations  or  combinations  of the Company with another
limited liability company or other entity.

     xi. Filing bankruptcy or seeking relief under any debtor relief law.

     xii. The admission of any new Member or the issuance of any interest in the
Company to any party.

     xiii. The determination of "Available Excess Earnings."

                           xiv.  The  determination  to not  make  Distributions
                  otherwise    required   by   this   Agreement,    making   any
                  disproportionate  distribution to a Member of cash or property
                  in-kind, or, subject to the provisions of Section 8.11, making
                  any  distribution of cash or property to any Manager in his or
                  her capacity as a Manager;

                           xv.  Sale,   lease  or  other   transfer  of  all  or
                  substantially  all of the  Company's  assets,  or any material
                  amount of the  Company's  assets  other  than in the  ordinary
                  course of the Company's business.

                           xvi.    Borrowing   or    incurring    any   material
                  indebtedness, other than open accounts payable to unaffiliated
                  third  parties,  guaranteeing  any  material  indebtedness  or
                  obligation  of  any  party,  or  granting  any  collateral  or
                  security  interest in Company  property  to secure  payment or
                  performance of any indebtedness, obligation, or guaranty.

                           xvii.  Purchasing or leasing  assets or property,  or
                  entering into any contract or obligation,  which obligates the
                  Company to pay in excess of $10,000 in the aggregate in one or
                  any series of installments.

     xviii. Causing a material change in the nature of the Company's business or
the legal name of the Company.

                           xix. Entering into a transaction or other action with
                  any Manager, officer or Member not otherwise described in this
                  Section 8.9 that is not fair and  reasonable to the Company or
                  the Members or that would be  considered a breach of fiduciary
                  duty.

     xx.  Materially  reducing  the  amount or scope of the  insurance  coverage
described  in  Schedule  3.10  to the  Contribution  Agreement,  except  for the
addition of the  additional  assureds  described on Schedule  3.10.  The Company
covenants  to  continuously  maintain  said  insurance  coverage  for so long as
Caster, Inc. is a Member.

                           xxi.  Taking any other action which,  by the terms of
                  this  Agreement,  requires the approval or consent of not less
                  than sixty-six percent (66%) of the Members.

                           xxii.   Settling  any  actual  or  threatened  claim,
                  litigation,   or  regulatory  proceeding,  or  confessing  any
                  judgment,  arising  out of or  connected  with any  actual  or
                  alleged error, omission,  negligence, or willful misconduct of
                  Caster.

                           xxiii. Issuing any new Membership Interests that will
                  reduce the Membership  Interests of the existing Members other
                  than on a pro rata basis.

                           xxiv. Taking any action, making any determination, or
                  making any  election  with  respect to a right  granted to the
                  Managers pursuant to Section 1.7, Article V or Article VI.

     xxv.  Engaging in any act or transaction  not in the ordinary course of the
Company's business.

                  (c)  Notwithstanding  any other  provision  contained  in this
         Agreement requiring the unanimous vote of the Members or the consent of
         Caster,  Inc. or Caster,  Inc.'s designated  Manager, as long as Caster
         has not  breached the  provisions  of ARTICLE VIII or ARTICLE IX of the
         Contribution  Agreement,  the  following  acts or  transactions  by, or
         involving,  the Company may not be taken  without  first  obtaining the
         written consent of (A) Caster, Inc., any person to whom Caster,  Inc.'s
         Membership  Interest has been  rightfully  transferred  pursuant to the
         Section 2.5, or the Manager  designee of Caster,  Inc.,  and (B) Prime,
         any person to whom  Prime's  Membership  Interest  has been  rightfully
         transferred pursuant to the Section 2.5, or each of the two (2) Manager
         designees of Prime;  provided,  however, that no written consent of any
         party is required under this subsection to take a particular  action if
         (but only to the  extent  that)  such  action is  required  to be taken
         pursuant  to the  express  terms  and  provisions  of the  Contribution
         Agreement:

     i.  Mergers,  consolidations  or  combinations  of the Company with another
limited liability company or other entity.

     ii. Filing bankruptcy or seeking relief under any debtor relief law.

                           iii. Taking any action, making any determination,  or
                  making any  election  with  respect to a right  granted to the
                  Managers pursuant to Section 1.7, Article V or Article VI.

                           iv.  Sale,   lease  or  other   transfer  of  all  or
                  substantially  all of the  Company's  assets,  or any material
                  amount of the  Company's  assets  other  than in the  ordinary
                  course of the Company's business.

                           v. Entering  into a transaction  or other action with
                  any Manager, officer or Member not otherwise described in this
                  Section 8.9 that is not fair and  reasonable to the Company or
                  the Members or that would be  considered a breach of fiduciary
                  duty.

     vi. Taking any other action which, by the terms of this Agreement, requires
the approval or consent of not less than sixty-six percent (66%) of the Members.

     vii.  Issuing any new Membership  Interests that will reduce the Membership
Interests of the existing Members other than on a pro rata basis.

                           viii.   The   determination   of  "Available   Excess
                  Earnings";   provided,   that  this  will  not   prevent   the
                  accumulation  and  non-distribution  by the Company of six (6)
                  times the average monthly Available Excess Earnings  (averaged
                  using the  preceding  six (6)  months)  after  satisfying  any
                  obligation to distribute Available Excess Earnings pursuant to
                  Section 5.2 hereof.

                           ix.  The  determination  to  not  make  Distributions
                  otherwise    required   by   this   Agreement,    making   any
                  disproportionate  distribution to a Member of cash or property
                  in-kind, or, subject to the provisions of Section 8.11, making
                  any  distribution of cash or property to any Manager in his or
                  her capacity as a Manager;

     x.  Engaging in any act or  transaction  not in the ordinary  course of the
Company's business.

                           xi.   Notwithstanding   the  provisions  of  Sections
                  8.9(b)(vi)  and  8.9(b)(ix),  waiving,  refusing  to  enforce,
                  amending,  restating,  superseding  or  modifying  any  of the
                  provisions  of  this  Agreement  or any  Transaction  Document
                  (including  the  Facility Use  Agreement)  with respect to any
                  matter described in this Section 8.9(c).

                           xii. Unless Caster is no longer exclusively using the
                  Company's  facilities  in the manner  contemplated  in Section
                  9.3(a) of the  Contribution  Agreement  (regardless of whether
                  Section 9.3(a) is then enforceable),  materially  reducing the
                  amount  or  scope  of  the  insurance  coverage  described  in
                  Schedule 3.10 to the  Contribution  Agreement,  except for the
                  addition  of the  additional  assureds  described  on Schedule
                  3.10.  The Company  covenants to  continuously  maintain  said
                  insurance coverage for so long as Caster, Inc. is a Member.

                  (d) Any of the above actions taken by the Company  without the
         necessary approval pursuant to Section 8.9(b) or Section 8.9(c) is void
         ab initio.  A Member shall be deemed to have  materially  breached this
         Agreement if the Company,  acting pursuant to the apparent authority of
         the Manager designee(s) of such Member,  takes any of the above actions
         without the necessary  approval  pursuant to Section  8.9(b) or Section
         8.9(c).

         Section 8.10.  Committees.  The Managers  may, by resolution  passed by
sixty-six percent (66%) 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,  as long as Caster  has not  delivered  the
written notice described in Section 9.3(a) of the Contribution  Agreement,  must
be a Manager designee of Caster,  Inc.),  which committees shall have such power
and  authority  and shall  perform  such  functions  as may be  provided in such
resolution  (subject to applicable law), which in all events shall be consistent
with the other  provisions of this Agreement and the  Transaction  Documents and
shall not be contrary to the provisions of Section 8.9 of this  Agreement.  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.

         The foregoing paragraph notwithstanding, the Managers shall establish a
Medical  Executive  Committee,  the  size  and  composition  of  which  shall be
established  by the  affirmative  vote or  written  consent  of two of the three
Managers  (one of whom must,  as long as Caster has not  delivered  the  written
notice described in Section 9.3(a) of the Contribution Agreement, be the Manager
designee of Caster,  Inc.).  Members of the Medical Executive  Committee must be
licensed  physicians,  but need not be  Members,  Managers,  or  officers of the
Company.  The Medical Executive Committee shall meet at such time or times as it
may, by majority  vote of its members,  elect and may adopt  procedures  for the
conduct of its meetings.  The Medical  Executive  Committee shall have authority
and control over the nonprofessional  medical aspects of the Company's business,
and shall  provide  advice to the  Managers on  decisions  relating to equipment
purchases,  technological obsolescence,  quality assurance,  credentialing,  and
such other matters as shall be requested by the Managers.  The Medical Executive
Committee  shall be advisory  only and shall not have the  authority to bind the
Company.  The majority of the members of the Medical  Executive  Committee shall
constitute a quorum for the transaction of its business and the affirmative vote
of the  majority  of  the  members  of the  Medical  Executive  Committee  shall
constitute action validly taken by that body; provided,  however,  that a quorum
shall not be deemed to exist  unless,  as long as Caster has not  delivered  the
written notice  described in Section 9.3(a) of the Contribution  Agreement,  the
Manager designee of Caster,  Inc. has been given reasonable prior notice of such
meeting and an opportunity to participate in such meeting.

         Section  8.11.  Compensation  of Managers.  The  Members,  by unanimous
approval,  shall  have  the  authority  to  provide  that any one or more of the
Managers  shall  be  compensated,  and  may,  by  unanimous  approval,  fix  any
compensation  (which may include  expenses) they elect to pay to any one or more
of the Managers.

         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 any meeting
of  the  Managers  or  such  committee  by  telephone  (including  a  conference
telephone)  or similar  communications  equipment  by means of which all persons
participating in the meeting can hear each other, and such 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,  except as expressly
provided  otherwise  in an  agreement  between  the  Manager  and the Company or
another party.

         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 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;  Brad Hummel,  President;  Teena  Belcik,  Vice
President,  Secretary and Treasurer;  Mark Rosenberg, Vice President; and Andrew
Caster,  M.D.,  Vice  President.  The officers of the Company  shall have powers
commensurate  with the corporate powers  ordinarily  associated their respective
titles, as limited, extended or otherwise modified pursuant to any resolution of
the Managers,  and otherwise consistent with the terms of this Agreement and the
Transaction Documents.

                                   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 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   provision  of  the  Contribution  Agreement.   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 Contribution Agreement; 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 Contribution Agreement.

                                  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  full  name  and  last  known
         business or  residence  address of each Member and of each holder of an
         economic  interest  in the  Company  set forth in  alphabetical  order,
         together  with the Capital  Contributions  and share in Net Profits and
         Net Losses of each Member and holder of an economic interest;

     (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  pursuant to
         which any of the foregoing were executed;

                      (d)  Copies  of the  Company's  federal,  state  and local
         income tax or information returns and reports, if any, for the six most
         recent fiscal 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;
provided,  however,  if such act  requires  the  approval  of the Members of the
Managers, such approval has first been obtained.

         Section 12.5.  Checks.  Subject to the provisions of Section 8.9(b)(v),
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 Managers,  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. Subject to the provisions of Section 8.9(b)(v), 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,  but in no event  later than April 15
immediately following the end of such fiscal year, 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 Members
regarding this Agreement or any other Transaction  Document,  any claims arising
out of any breach or alleged breach of this  Agreement or any other  Transaction
Document,  and any claims  arising out of the  relationship  between the Members
created  hereunder,  shall be  submitted to binding  arbitration  by all Members
involved in accordance  with the  procedures  for  arbitration  contained in the
Contribution Agreement.

     Section 12.10.  Authority to Execute  Facility Use  Agreement.  The Members
hereby  authorize  the  Managers  to execute  and  deliver to Caster,  Inc.  the
Facility Use Agreement attached to the Contribution Agreement as Exhibit C.

         Section 12.11. Cross Default; Remedies. Each of the Members agrees that
a breach  by it (or any  entity  controlling,  controlled  by,  or under  common
control with it) of any of the provisions of the  Contribution  Agreement or any
other Transaction Document shall also be deemed to be a breach of this Agreement
(subject  to any  right to cure  provided  with  respect  to such  breach).  The
remedies  contemplated  provided in Section  9.7(a) and (b) of the  Contribution
Agreement shall in all events be the exclusive  remedies for any and all acts or
omissions of Caster that result in a material breach of any of the provisions of
Article  VIII and  Article  IX  thereof,  regardless  of  whether  such  acts or
omissions, in the absence of this sentence, would give rise to a claim under any
of the Transaction Documents.

         Section 12.12 Expenses.  Each Member agrees that,  notwithstanding  the
prior  practices  associated  with the Business (as defined in the  Contribution
Agreement) as conducted prior to the Closing Date, all liabilities, obligations,
costs and  expenses  that arise after the Closing  Date and are personal to such
Member (or arose from  transactions or occurrences that directly  benefited such
Member in a capacity other than as a Member) shall not be considered expenses of
the Company and shall be borne solely by such Member, unless agreed otherwise by
the unanimous  vote or written  consent of the Managers,  or unless (and only to
the extent)  provided  otherwise in the Facility Use Agreement.  With respect to
any such personal  expenses that were incurred  prior to the Effective  Time (as
defined in the Contribution  Agreement),  such expenses shall not be incurred or
reimbursed by, or charged to, the Company after the Effective Time.

         Section 12.13 Consents. To be valid and effective,  all consents of the
Managers or Members  required or permitted by this Agreement shall be in writing
and signed by each party giving consent.

                                  ARTICLE XIII.

                                   AMENDMENTS

         Section  13.1.  Amendments.  Except to the  extent  expressly  provided
otherwise herein, this Agreement may only be altered,  amended or repealed and a
new limited  liability  company  agreement  may only be adopted by the unanimous
vote of the  Members at any  regular  meeting of the  Members or at any  special
meeting of the Members  called for that  purpose,  or by  execution of a written
consent in accordance  with the provisions of Section 3.8.  Except to the extent
expressly  provided  otherwise  therein,  the  Certificate  of  Formation of the
Company,  and any other  corporate  governance  document of the Company,  or any
other document which  establishes,  creates or governs the relations between the
Members  or the  Managers  may  only be  altered,  amended  or  repealed  by the
unanimous  vote of the Members at any  regular  meeting of the Members or at any
special  meeting of the Members  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.

         Section 13.3. Integration with Contribution Agreement. To the extent of
any inconsistency between the provisions of the Contribution  Agreement and this
Agreement, the terms and provisions of the Contribution Agreement shall control.
Accordingly, no Member or Manager shall be deemed to have breached any fiduciary
duty  owed to any other  Member or the  Company  as a result  of  investing  in,
acquiring or developing any facility, business or operations that are related or
similar to, or in direct competition with, the Company's business if such act or
transaction  is allowed or not  prohibited by the  provisions of Article VIII of
the Contribution Agreement, or the termination of such provisions.

                            [Signature page follows]


<PAGE>


S-1

                                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 March, 2000.

                                       Caster Eye Center Medical Group

                                       ------------------------------------
                                       Andrew Caster, M.D., President

                                       Prime Refractive, L.L.C.



                                       Teena Belcik, Treasurer


<PAGE>


                                CONSENT OF SPOUSE

                  The  undersigned  spouse  of  Caster  acknowledges  on her own
             behalf that:  I have read the  foregoing  Agreement  and I know its
             contents.  I am aware  that by its  provisions  Caster  Eye  Center
             Medical  Group  grants  the  Company  certain  assets  that  may be
             community property and may restrict my ability to later transfer my
             community property interest in such assets, my spouse's interest in
             Caster Eye  Center  Medical  Group and  Caster  Eye Center  Medical
             Group's Membership Interest in the Company. I hereby approve of the
             provisions  of the  Agreement,  including  the  contribution  of my
             community property  interest,  if any, in the assets contributed to
             the  Company,  and agree that such  Membership  Interest  and Stock
             Interests and my interest in them are subject to the  provisions of
             the  Agreement and that I will take no action at any time to hinder
             operation of the  Agreement on such  Membership  Interest and Stock
             Interests or my interest in them.

                                         Jacqueline Caster


<PAGE>


                                       A-1

043838.0000  AUSTIN  167621 v12

                                    EXHIBIT A

                               OWNERSHIP INTERESTS

Name                               Contribution             Membership Interest

Prime                   Assets with agreed fair market                  60%

Caster, Inc.            Assets with agreed fair market                  40%
                        value of $244,325