Document:

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                                                                   EXHIBIT 10.15

                                SUPPLY AGREEMENT

                                     BETWEEN

                         ADVANCED CORNEAL SYSTEMS, INC.

                                       AND

                           BIOZYME LABORATORIES, LTD.

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                                TABLE OF CONTENTS

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ARTICLE 1 - DEFINITIONS..........................................................................1

        1.1    "Act".............................................................................1
        1.2    "ACS Vitrase(TM)Product"..........................................................1
        1.3    "ACS Corneaplasty(TM)Product".....................................................1
        1.4    "Equipment".......................................................................1
        1.5    "Facility"........................................................................1
        1.6    "FDA".............................................................................2
        1.7    "GMP Grade".......................................................................2
        1.8    "Good Manufacturing Practices"....................................................2
        1.9    "Ophthalmic Applications".........................................................2
        1.10   "Product".........................................................................2
        1.11   "Specifications"..................................................................2
        1.12   "Unit"............................................................................2

ARTICLE 2 - CERTIFICATION AND APPROVAL...........................................................2

        2.1    Certification.....................................................................2
        2.2    Milestone Payments................................................................3
        2.3    ACS Equipment.....................................................................3

ARTICLE 3 - SUPPLY...............................................................................4

        3.1    Product Supply....................................................................4
        3.2    Forecasts.........................................................................4
        3.3    Orders............................................................................5
        3.4    Form of Order.....................................................................5
        3.5    Annual Purchase Requirements......................................................6
        3.6    Pricing...........................................................................6
        3.7    Payment...........................................................................7
        3.8    Delivery..........................................................................7
        3.9    Shipping Requirements.............................................................7
        3.10   Title and Risk of Loss............................................................7

ARTICLE 4 - REPRESENTATIONS AND WARRANTIES.......................................................7

        4.1    Product Warranties................................................................7
        4.2    Testing Warranties................................................................8

ARTICLE 5 - QUALITY ASSURANCE REQUIREMENTS.......................................................9

        5.1    Release Testing...................................................................9
        5.2    Stability Testing.................................................................9
        5.3    Retains...........................................................................9
        5.4    Maintenance of Records............................................................9
        5.5    Inspection of Manufacturing Facility and Manufacturing Data.......................9
        5.6    FDA Inspection of Facility.......................................................10
        5.7    Subcontracting...................................................................10
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                                TABLE OF CONTENTS
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        5.8    Reprocessing......................................................................9

ARTICLE 6 - ACCEPTANCE OF PRODUCT...............................................................10

        6.1    Review of Results of Release Testing.............................................10
        6.2    Rejection of Product.............................................................10
        6.3    Results of Regulatory Authority Inspections......................................10

ARTICLE 7 - SHORTAGE OF SUPPLY..................................................................11

        7.1    Notification.....................................................................11
        7.2    Priority Allocation..............................................................11
        7.3    Other Remedies...................................................................11

ARTICLE 8 - INDEMNIFICATION.....................................................................

        8.1    Indemnity by ACS.................................................................
        8.2    Indemnity by Biozyme.............................................................
        8.3    Defense of Indemnification Claims................................................

ARTICLE 9 - CONFIDENTIALITY.....................................................................11

        9.1    Confidential Information.........................................................11

ARTICLE 10 - TERM...............................................................................12

        10.1   Term.............................................................................12
        10.2   Termination for Cause............................................................10
        10.3   Termination with Notice..........................................................13
        10.4   Effect of Expiration or Termination on Agreement.................................13
        10.5   Survival.........................................................................13

ARTICLE 11 - MISCELLANEOUS......................................................................13

        11.1   Suppliers........................................................................13
        11.2   Force Majeure....................................................................13
        11.3   Relationship of the Parties......................................................14
        11.4   Assignment.......................................................................14
        11.5   Entire Agreement.................................................................14
        11.6   Severability.....................................................................14
        11.7   Headings.........................................................................14
        11.8   Notices..........................................................................15
        11.9   Public Disclosure................................................................15
        11.10  Amendment; No Waiver.............................................................15
        11.11  No Conflict......................................................................16
        11.12  Governing Law....................................................................16
        11.13  No Strict Construction...........................................................16
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                                TABLE OF CONTENTS
                                  {CONTINUED)

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        11.14  Counterparts.... ................................................................16
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                                SUPPLY AGREEMENT

        This Supply Agreement (the "Agreement") is entered into as of the 23rd
day of September 1999 (the "Effective Date") by and between Biozyme
Laboratories, Ltd., a company incorporated in England and Wales under number
1034731 whose registered office is at Unit 6, Gilchrist Thomas Estate,
Blaenavon, Gwent, NP4 9RL, United Kingdom ("Biozyme") and Advanced Corneal
Systems, Inc., a California corporation ("ACS").

                                    RECITALS

        A. Biozyme has expertise in the production of particular animal sourced
hyaluronidase.

        B. ACS has developed products which utilize such particular animal
sourced hyaluronidase for use in ophthalmic applications.

        C. Biozyme wishes to supply to ACS, and ACS wishes to purchase from
Biozyme, quantities of the Product for use in its products and sale worldwide on
the terms and conditions set forth below.

        NOW, THEREFORE, the parties agree as follows:

                             ARTICLE 1 - DEFINITIONS

        1.1 "Act" means the United States Food, Drug and Cosmetics Act, as
amended from time to time and the regulations promulgated thereunder.

        1.2 "ACS Vitrase(R) Product" means a product containing hyaluronidase as
an active ingredient used to treat various diseases of the human eye.

        1.3 "ACS Corneaplasty(TM) Product" means a product system, containing
hyaluronidase as an active ingredient used to correct refractive vision errors
of the human eye.

        1.4 "Equipment" shall have the meaning set forth in Article 2.3.

        1.5 "Facility" means the facility at Biozyme Laboratories, Ltd.,
Blaenavon Gwent, South Wales, United Kingdom.

        1.6 "FDA" means the United States Food and Drug Administration.

        1.7 "GMP Grade" means Product that has been produced in accordance
with applicable Good Manufacturing Practices with respect to active
pharmaceutical ingredients.

        1.8 ."Good Manufacturing Practices" means the current good manufacturing
practices for manufacturing active pharmaceutical ingredients as set forth in 21
CFR Parts 210 and

<PAGE>   6

211 and the Rules Governing Medical Products in the European Community as set
forth in Volume IV; Guide to Good Manufacturing Practice for the Manufacturing
of Active Pharmaceutical Ingredients.

        1.9 "Ophthalmic Applications" means any application, whether research
or commercial, of the Product for administration to the human or animal eye.

        1.10 "Product" means animal sourced hyaluronidase manufactured in
accordance with the Specifications.

        1.11 "Specifications" means the manufacturing, quality control,
packaging, labeling, shipping and storage specifications for the Product, as set
forth in Exhibit A hereto or as otherwise mutually agreed in writing by ACS and
Biozyme from time to time.

        1.12 "Unit" means that amount of enzyme causing the same turbidity
reduction as the 'International Unit' (I.U.) as compared with the International
Standard meeting the applicable Specifications.

                     ARTICLE 2 - CERTIFICATION AND APPROVAL

        2.1 Certification. Promptly upon execution of this Agreement, but in
no event later than March 31, 2000, Biozyme will use best efforts to obtain
third party certification ("GMP Certification"), by an auditor acceptable to
both Biozyme and ACS, that the manufacture of Product by Biozyme at the Facility
is in compliance with GMP requirements. ACS shall bear the reasonable costs
associated with the third party audit and inspection of the Facility as
requested by ACS. ACS shall also bear the costs of outside laboratory testing
for the new water system and cleaning validations as required to obtain GMP
certification. Biozyme shall bear the costs in connection with the modification
or improvement of the Facility including certain improvements to Unit 15, cold
rooms 1 and 2 and laboratory 3 as required in order to obtain certification of
compliance with GMP requirements.

        2.2 Milestone Payments. Upon receipt of GMP certification pursuant to
Article 2.1 above, ACS shall pay to Biozyme Pound Sterling40,000 (British
Pounds). In addition, ACS shall pay to Biozyme, Pound Sterling20,000 (British
Pounds) immediately upon the occurrence of each of: (i) FDA approval of a New
Drug Application ("NDA") for the ACS Vitrase(R) product; and (ii) FDA approval
of an NDA for the ACS Corneaplasty(TM) product system.

        2.3 ACS Equipment.

               2.3.1 ACS shall acquire, in a timely manner and at its own
expense, and install or have installed at the Facility, the equipment listed in
Exhibit B attached hereto ("Equipment"). Biozyme shall not utilize the Equipment
for any use other than for the manufacture of the Product for ACS. The Equipment
shall, at all times, remain the sole and exclusive property of ACS.

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               2.3.2 Biozyme, at its expense, shall make all necessary site
preparations and cause the Equipment to be operated in accordance with any
applicable operating manuals, manufacturer's instructions and GMP requirements.
Biozyme shall effect and bear the reasonable expense of all necessary repair,
maintenance and operation of the Equipment. Replacements required to be made to
maintain the Equipment in good condition, reasonable wear and tear excepted, and
to comply with all applicable laws to which the use and operation of the
Equipment may be or become subject shall be subject to the prior written
approval of ACS, the cost of which shall be the responsibility of ACS. All
replacement Equipment and parts furnished in connection with such maintenance or
repair shall immediately become the property of ACS and part of the Equipment
for all purposes hereof. All such maintenance and repair services shall be
immediately paid for and discharged by Biozyme with the result that no lien
under any applicable laws will attach to the Equipment as a result of the
performance of such services or the provision of any such material.

               2.3.3 Biozyme shall obtain and maintain for the term of this
Agreement, at its own expense, (a) "all risk" insurance against loss or damage
to the Equipment, (b) commercial general liability insurance (including
contractual liability, products liability and completed operations coverage)
reasonably satisfactory to ACS.

               2.3.4 If any items of Equipment shall become lost, stolen,
destroyed, or damaged beyond repair for any reason, or in the event of
condemnation, confiscation, seizure or requisition of title to or use of such
items (collectively, an "Event of Loss"), Biozyme shall promptly pay to ACS the
fair market value of the Equipment subject to the Event of Loss as determined by
an objective third party evaluator agreeable to both parties. Upon payment of
such amount by Biozyme, ACS will transfer to Biozyme, "AS IS, WHERE IS, WITHOUT
RECOURSE, REPRESENTATION OR WARRANTY," all of ACS's right, title and interest,
if any, in such items of Equipment.

               2.3.5 (a) ACS and Biozyme confirm their intent that title to the
Equipment shall remain in ACS (or its successors and assigns) exclusively. If
requested by ACS, Biozyme, at ACS's cost, will affix plates or markings on the
Equipment and on any operating manuals and manufacturer's instructions
indicating the interests of ACS and its assigns therein, and Biozyme will not
allow any other indicia of ownership or other interest in the Equipment to be
placed on the Equipment. Biozyme shall not sell, assign, grant a security
interest in, sublet, pledge, hypothecate or otherwise encumber or suffer a lien
upon or against the Equipment.

                      (b) Location. Biozyme may move such Equipment from the
Facility only if Biozyme gives at least thirty (30) days prior written notice of
the relocation or such other documentation as ACS reasonably requests to protect
its interest in the Equipment.

                      (c) Biozyme shall keep copies of all operating manuals and
manufacturer's instructions with respect to the Equipment in good condition at
the Facility.

               2.3.6 In the event ACS should decide to sell or otherwise dispose
of any or all of the Equipment, Biozyme shall have the right of first refusal to
purchase such Equipment at ACS' good faith determination of the Equipment's fair
market value. If Biozyme elects not to

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purchase the Equipment under this Article 2.3.6, Biozyme shall, at ACS's
expense, return the Equipment to ACS in the same condition as delivered, normal
wear and tear expected, at such location as ACS shall designate.

                               ARTICLE 3 - SUPPLY

        3.1 Product Supply. Subject to the terms and conditions of this
Agreement, Biozyme shall supply ACS with ACS's requirements for Product, which
shall not be less than the minimum quantities of the Product set forth in
Article 3.5, during the term of this Agreement. Biozyme agrees that it shall not
manufacture Product for any third party for use in Ophthalmic Applications, and
shall not authorize any third party to manufacture or produce the Product for
third parties for use in Ophthalmic Applications.

        3.2 Forecasts. During the term of this Agreement, at least sixty (60)
days prior to the start of each calendar quarter ("Q1"), ACS shall provide
Biozyme with a rolling written forecast of the quantities of Product estimated
to be required on a quarterly basis during Q1 and the next three (3) quarters
("Q2" through "Q4").

        3.3 Orders. ACS shall place orders with Biozyme at any time for
delivery of the Product specifying the amount of Product ordered and required
delivery date(s). Biozyme shall accept such orders from ACS, subject to the
terms and conditions of this Agreement, provided that Biozyme shall not be
obligated to accept orders for any given quarter to the extent the quantity
ordered exceeds 120% of the quantity forecast in the forecast provided under
Article 3.2 above for the immediately preceding calendar quarter, but shall use
good faith efforts to fill orders for such quantities from available supplies.
Upon acceptance by Biozyme, each ACS order shall be final and not subject to
modification without the consent of Biozyme.

        3.4 Form of Order. ACS's orders shall be made pursuant to a written
purchase order, and shall provide for shipment in accordance with reasonable
delivery schedules as may be agreed upon from time to time in writing by Biozyme
and ACS.

               3.4.1 All sales of the Product pursuant to this Agreement shall
        be subject to the standard terms and conditions of sale of Biozyme from
        time to time set out in Biozyme Laboratories Ltd. catalogue, except to
        the extent that any provision of those terms and conditions of sale is
        inconsistent with any provisions of this Agreement in which event the
        latter shall prevail; or

               3.4.2 Biozyme and ACS agree in writing to vary those terms and
        conditions of sale.

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        3.5 Annual Purchase Requirements. ACS shall be required to order the
following minimum quantities of Product during the initial five (5) calendar
years following the Effective Date. ACS orders for non-GMP Product during
calendar year 1999 shall be applied to the Annual Purchase Requirements for 1999
as defined below.

<TABLE>
<S>                                           <C>
                                 1999         250 million Units

                                 2000         350 million Units

                                 2001         500 million Units

                                 2002         1,200 million Units

                                 2003         1,500 million Units
</TABLE>

        3.6 Pricing.

               3.6.1 Prices for commercial supply of the Product shall be as
follows:

                      (a) For orders providing for shipments of less than 100
million Units, $451 United States Dollars per million Units:

                      (b) For orders providing for shipments of 101 to 200
million Units, $428 United States Dollars per million Units: or

                      (c) For orders providing for shipments of more than 201
million Units, $410 United States Dollars per million Units:

               3.6.2 Any increase in the pricing for Product after the initial
two years of the agreement shall be presented to ACS by Biozyme not later than
ninety (90) days prior to the proposed effective date of the pricing change and
shall provide justification for the pricing increase. In no event shall such
pricing increase (i) be applicable to purchase orders accepted by Biozyme prior
to the effective date of the pricing change and (ii) in no event shall exceed
five percent (5%) per annum, unless such increase is due to a documented
increase in Biozyme's cost for the purchase of ovine raw material.

               3.6.3 Pricing for Product as defined in Article 3.6.1 above shall
be applicable to GMP Grade Product. Pricing for non-GMP Grade Product shall be
$410 USD per million units.

               3.6.4 Notwithstanding Article 3.6.2, Biozyme shall be entitled to
        increase the price of the Product to cover extra expenses which are a
        direct result of changes to the Specifications requested by ACS.

        3.7 Payment. Upon shipment of the Product, Biozyme will generate and
deliver to ACS an invoice for the quantities delivered. ACS shall remit payment
to Biozyme within thirty-five (35) days of such invoice date.

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        3.8 Delivery. Biozyme shall provide delivery of the Product, subject to
the provisions in Article 3.3 as follows:

                      (a) ACS orders for shipments of Product less than 60
million units: within forty-five (45) days of receipt of ACS order.

                      (b) ACS orders for shipments of Product more than 60
million units: within ninety (90) days of receipt of ACS order.

        3.9 Shipping Requirements. Biozyme shall be responsible for arranging
for shipment of Product in accordance with shipping instructions which ACS shall
provide to Biozyme reasonably in advance of any such shipment (including,
without limitation, destination point and courier). Prior to delivering Product
to the courier, Biozyme shall package the material in accordance with good
commercial practice with respect to protection of the Product during
transportation and to comply with any applicable regulations and government
requirements. ACS shall be responsible for (i) obtaining all governmental
permits, consents and approvals which are required in order to export Product
from the United Kingdom and import the Product into the country of destination,
and (ii) making any notifications or other filings (whether before or after
shipment) which are required in connection with the exportation of Product from
the United Kingdom or importation of Product into the country of destination.
All out-of-pocket costs associated with freight insurance and custom duties, as
well as any special packaging expenses shall be paid by ACS.

        3.10 Title and Risk of Loss. Title and risk of loss or damage shall
pass to ACS upon delivery of Product to the courier approved by ACS. In all
cases, delivery of Product shall be FOB point of shipment.

                   ARTICLE 4 - REPRESENTATIONS AND WARRANTIES

        4.1 Product Warranties. Biozyme represents and warrants for the
period of this Agreement and for the twelve months immediately following
termination that (i) each shipment of Product will conform to the
Specifications, and all Product produced under this Agreement shall be GMP Grade
following completion of the GMP certification as specified in Article 2.1, (ii)
its standard manufacturing procedures conform to the applicable requirements of
all applicable Specifications at the time it is shipped hereunder, and (iii) to
the best of Biozyme's knowledge, the Product does not infringe the intellectual
property rights of any third party.

        4.2 Testing Warranties. Biozyme represents and warrants for the
period of this Agreement and for the twelve months immediately following
termination that it shall use due care in conducting the testing specified in
Article 5 hereof and shall perform all such testing in accordance with the terms
of this Agreement and generally prevailing industry standards.

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                   ARTICLE 5 - QUALITY ASSURANCE REQUIREMENTS

        5.1 Release Testing. Biozyme shall be responsible for all quality
control testing and analysis of Product outlined in Exhibit C to ensure that it
conforms to the Specifications and the warranties set forth in Article 4.1
hereof (the "Release Testing"). Biozyme shall provide ACS, at the time the
Product is shipped, with the results of all Release Testing, together with a
Certificate of Analysis relating to such testing, in order to enable ACS to
review such data in accordance with the provisions of Article 5 hereof.

        5.2 Stability Testing. Biozyme shall be responsible for conducting
stability testing of the Product in accordance with the provisions of Exhibit D
hereto. Product required for Stability Testing pursuant to Exhibit D will be
provided by ACS to Biozyme at no cost from Product purchased under this
Agreement.

        5.3 Retains. Biozyme shall retain a sufficient quantity of each
production run of Product to enable the performance of the tests required by
this Article 5 at least twice. Such samples shall be retained during such period
as is required by the Specifications, GMP requirements and all applicable
regulatory requirements.

        5.4 Maintenance of Records. Biozyme shall keep, for a period of seven
(7) years following the end of the relevant calendar quarter, or such longer
period as shall be required by the Act or the applicable regulatory authorities
in any jurisdiction in which the Product is sold, exact, true and complete
records of all operations involved in the manufacture, testing, storage and
shipping of Product produced in such calendar quarter.

        5.5 Inspection of Manufacturing Facility and Manufacturing Data.
Biozyme will permit ACS representatives or its designates to visit the Facility,
during normal working hours and with reasonable prior written notice, to observe
the performance of the manufacturing, handling, storage and shipping of Product
hereunder, discuss such activities with appropriate officials of Biozyme,
inspect (and if reasonably necessary copy) all records and data required to be
maintained pursuant to this Article 5, and analyze any tangible material
relevant thereto which is then within Biozyme's control and which is reasonably
available for such testing. Biozyme will cooperate with ACS and any governmental
authority in evaluating any complaint or claim by such governmental authority,
or adverse drug reaction report, related to the Product, and shall provide
information and take such other steps as may be necessary or appropriate to
comply with all requirements imposed by any regulatory authority in any
jurisdiction in which the Product is sold with respect to the Product. ACS shall
be entitled to exercise its rights pursuant to this Article 5.5 until the
expiration of the record retention period described in Article 5.4.

        5.6 FDA Inspection of Facility. Biozyme shall promptly provide ACS
with any correspondence and other documentation received from or provided to
FDA, United Kingdom or European regulatory authorities in connection with
inspection of the Facility, including without limitation any post-inspection
reports and any Establishment Inspection Reports.

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        5.7 Subcontracting. It is understood that in fulfilling its obligations
hereunder, Biozyme may subcontract such obligations for the testing pursuant to
Articles 5.1 - 5.2; provided that Biozyme shall at all times be responsible to
ACS for the performance of such subcontractors.

        5.8 Reprocessing. Reprocessing of the Product at any stage of its
manufacture will not be permitted unless so authorized in writing by ACS.

                        ARTICLE 6 - ACCEPTANCE OF PRODUCT

        6.1 Review of Results of Release Testing. ACS shall promptly accept
all Units of Product supplied to it in accordance with this Agreement, but shall
have the right to reject any Product which does not meet the Specifications
according to the manufacturing records and results of the Release Testing
relating to such Product. ACS agrees to review such data and records and
indicate to Biozyme in writing within thirty (30) calendar days after receipt
thereof whether it accepts the applicable Product or rejects such Product for
failure to meet the Specifications or, if both Biozyme and ACS agree in writing
to delay its response for a mutually agreed upon period of time. In the event
that ACS shall not have so rejected Product in writing within the thirty-day
time period described above, ACS shall be deemed to have accepted such Product.
It is understood and agreed that ACS's review of data or its acceptance (or
deemed acceptance) of Product pursuant to the provisions of this Article 6.1
shall in no way modify or diminish Biozyme's obligation hereunder.

        6.2 Rejection of Product. If ACS rejects any Product, then it shall
provide Biozyme with a reasonably detailed description of the basis for such
rejection. Within thirty (30) business days of receiving ACS's notice of
rejection, Biozyme shall notify ACS as to whether it agrees with such rejection.

        6.3 Results of Regulatory Authority Inspections. In no event shall
ACS be required to accept any Product in the event that the results of any FDA,
United Kingdom or European regulatory authority inspection of the Facility
indicate that the Facility was not being operated at the time the Product was
produced, or the Product is not being manufactured, handled, stored, packaged or
shipped, in accordance with the applicable regulatory standards.

                         ARTICLE 7 - SHORTAGE OF SUPPLY

        7.1 Notification. If at any time Biozyme becomes unable to supply
requirements for the Product, or becomes aware that it will be unable to supply,
Biozyme shall promptly notify ACS in writing. In such event, representatives
from ACS and Biozyme shall, at their own expense and at their earliest
opportunity, convene to address the problem, including locating alternative
suppliers and/or facilities to increase production and any other actions
necessary to resolve the problem.

        7.2 Priority Allocation. During the term of the Agreement, and in
accordance with Article 3, Biozyme shall provide ACS with a priority allocation
of ovine raw materials used to

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manufacture the product and shall not allocate ovine raw materials to other
manufacturing operations until ACS requirements pursuant to Article 3.3 are
satisfied.

        7.3 Other Remedies. In the event that Biozyme fails to supply to ACS
quantities of Product that Biozyme is otherwise obligated to supply under this
Agreement, and such failure is the result of Biozyme's willful breach of its
obligations hereunder or its gross negligence, the remedies in Articles 7 and 9
shall not be exclusive and ACS shall be entitled to damages and/or other
remedies legally available. In the event that ACS fails to purchase the minimum
quantities of Product set forth in Article 3.5, Biozyme shall be entitled to
terminate the Agreement forthwith and shall be entitled to damages in line with
outstanding minimum purchases; provided however, that ACS may fulfill its
obligations to Biozyme under Article 3.5 by rendering to Biozyme a payment in
the amount equal to that which would be paid to Biozyme for such minimum
purchases.

                           ARTICLE 8 - CONFIDENTIALITY

        8.1 Confidential Information.

               8.1.1 Confidentiality. All information submitted by one party to
the other in connection with this Agreement identified as confidential at the
time of disclosure shall be considered as confidential ("Confidential
Information") and shall be utilized only pursuant to the purposes set forth
hereunder. During the term of this Agreement and for a period of five (5) years
thereafter, neither party shall disclose to any third party any Confidential
Information received from the other party without the specific written consent
of such party. The foregoing shall not apply where such information: a) was or
becomes public through no fault of the receiving party, b) was, at the time of
receipt, already in the possession of receiving party as evidenced by its prior
written records, c) was obtained from a third party legally entitled to use and
disclose the same, d) is independently developed by the receiving party without
use of any Confidential Information of the disclosing party, or e) is required
by law to be disclosed to a court or governmental agency.

               8.1.2 Permitted Use and Disclosures. Notwithstanding Article
8.1.1 above, each party hereto may use or disclose information disclosed to it
by the other party to the extent such use or disclosure is reasonably necessary
in filing or prosecuting patent applications, prosecuting or defending
litigation, complying with applicable governmental regulations or otherwise
submitting information to tax or other governmental authorities, conducting
clinical trials, making a permitted sublicense or otherwise exercising its
rights hereunder, provided that if a party is required to make any such
disclosure of another party's confidential information, other than pursuant to a
confidentiality agreement, it will give reasonable advance notice to the latter
party of such disclosure and, save to the extent inappropriate in the case of
patent applications, will use its best efforts to secure confidential treatment
of such information prior to its disclosure (whether through protective orders
or otherwise).

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               8.1.3 Confidential Terms. Except as expressly provided herein,
each party agrees not to disclose any terms of this Agreement to any third party
without the consent of the other party; provided, disclosures may be made as
required by securities or other applicable laws, or London Stock Exchange
requirements, or to actual or prospective investors or corporate partners, or to
a party's accountants, lenders, attorneys and other professional advisors.

                                ARTICLE 9 - TERM

        9.1 Term. This Agreement shall be effective as of the Effective Date
and, unless earlier terminated in accordance with the provisions of this Article
9, shall continue in full force and effect until terminated by mutual agreement
of the parties or as provided under Article 9.2 below.

        9.2 Termination for Cause.

               9.2.1 At any time prior to expiration pursuant to Article 9.1,
either party may terminate this Agreement for cause upon written notice to the
other party in the event that there has been a material breach by the other
party of any of the terms of this Agreement and the other party has failed to
cure such breach within sixty (60) days after receipt of written notice thereof.
Such termination rights shall be in addition to and not in substitution for any
other remedies that may be available to the party serving such notice against
the party in default. Termination pursuant to this Article 9 shall not relieve
the party in default from liability and damages to the other party for breach.
Waiver by either party of a single default or a succession of defaults shall not
deprive such party of any right to terminate this Agreement arising by reason of
any subsequent default.

               9.2.2 ACS may terminate this Agreement if third party GMP
Certification for the manufacture of the ACS Hyaluronidase is not received by
December 31, 2000.

               9.2.3 ACS may terminate this Agreement if Biozyme fails to
satisfy its obligations under Article 3.

        9.3 Termination with Notice. ACS may terminate the agreement upon
twelve months prior written notice to Biozyme. At the end of this twelve-month
period and following delivery of all outstanding orders, ACS shall purchase
Biozyme's remaining inventory of ovine raw material which was acquired to
fulfill ACS requirements as defined under Article 3.

        9.4 Effect of Expiration or Termination on Agreement. Termination of
this Agreement shall not relieve the parties of any obligation occurring or
incurred prior to such termination, including without limitation, any obligation
of ACS to pay for Product which has been manufactured prior to termination. In
addition, and without limiting the foregoing, in the event of any termination of
this Agreement, Biozyme may elect to either terminate all obligations to supply
further Product to ACS hereunder, or to continue to supply to ACS all quantities
of Product that ACS has ordered under then outstanding orders and any quantities
that ACS would be obligated to order under Article 3.3 above.

                                      -10-
<PAGE>   15

        9.5 Survival. The rights and obligations of the parties set forth in
Articles 4, 5.3, 5.4, 5.5 and 8 shall survive and remain in full force and
effect after the expiration, cancellation or termination of this Agreement for
any reason pursuant to the period of time specified in each of these Articles.

                           ARTICLE 10 - MISCELLANEOUS

        10.1 Suppliers. Without limiting Biozyme's responsibility under this
Agreement, Biozyme shall have the right at any time to satisfy its supply
obligations to ACS hereunder either in whole or in part through arrangements
with third parties engaged to perform services or supply facilities or goods in
connection with the manufacture, testing, and/or packaging of Product, however,
ACS shall receive prior written notice of any proposed change in the suppliers
of the raw material used to manufacture the Product.

        10.2 Force Majeure. Neither party to this Agreement will be liable to
the other party for failure or delay in the performance of any of its
obligations hereunder, if such failure or delay is due to causes beyond its
reasonable control, including, but not limited to, acts of God, earthquakes,
fires, strikes, acts of war, or intervention of any governmental authority, but
any such delay or failure will be remedied by such party as soon as possible
after the removal of the cause of such failure or delay.

        10.3 Relationship of the Parties. For all purposes of this Agreement,
Biozyme and ACS will be deemed to be independent entities, and anything in this
Agreement to the contrary notwithstanding, nothing herein will be deemed to
constitute Biozyme and ACS as partners, joint venturers, co-owners, or any
entity separate and apart from each party itself, nor will this Agreement
constitute any party hereto an employee or agent, legal or otherwise, of the
other party for any purposes whatsoever. Neither party hereto is authorized to
make any statements or representations on behalf of the other party or in any
way obligate the other party, except as expressly authorized in writing by the
other party. Anything in this Agreement to the contrary notwithstanding, except
as expressly provided in this Agreement, no party hereto will assume nor will be
liable for any liabilities or obligations of the other party, whether past,
present or future.

        10.4 Assignment. This Agreement may not be assigned by either party
without the prior written consent of the other party, except that either party
may assign this Agreement, in whole or in part, to the successor (including the
surviving company in any consolidation, reorganization or merger) or assignee of
all or substantially all of its business. This Agreement will be binding upon
any permitted assignee of either party. No assignment permitted hereunder will
have the effect of relieving any party to this Agreement of any obligations
hereunder.

        10.5 Entire Agreement. This Agreement and the exhibits hereto sets
forth the entire understanding between the parties relating to the subject
matter contained herein and may not be modified, amended or discharged except as
expressly stated in this Agreement or by a written agreement signed by the
parties hereto.

                                      -11-
<PAGE>   16

        10.6 Severability. If any provision of this Agreement is held by a
court of competent jurisdiction to be invalid or unenforceable, it will be
modified, if possible, to the minimum extent necessary to make it valid and
enforceable or, if such modification is not possible, it will be stricken and
the remaining provisions will remain in full force and effect; provided,
however, that if a provision is stricken so as to significantly alter the
economic arrangements of this Agreement, the party adversely affected may
terminate this Agreement upon sixty (60) days' prior written notice to the other
party.

        10.7 Headings. The headings set forth at the beginning of the various
sections of this Agreement are for reference and convenience and will not affect
the meanings of the provisions of this Agreement.

        10.8 Notices. Any required notices under this Agreement will be in
writing and be given by either party to the other in or by facsimile
transmission or by letter sent via courier, and sent to the address or place of
business of the other party as shown below and the notice will operate and be
deemed to have been given at the earliest of either the time of delivery or at
expiration of one business day from the date of the facsimile transmission or
three business days from the date the letter is deposited with the courier
service, and proof that the fax or telegram was sent or that the letter was
properly addressed and deposited will be sufficient evidence of service.

    Any such notice given to Biozyme will be addressed to:

        Biozyme Laboratories, Ltd.
        Unit 6, Gilchrist Thomas Estate
        Blaenavon, Gwent NP4 941
        South Wales
        United Kingdom
        Attn: John Chesham, Ph.D.
        Managing Director

    Any notice to be given to ACS will be addressed to:

        Advanced Corneal Systems, Inc.
        15279 Alton Pkwy
        Suite 100
        Irvine, California  92618 USA
        Attn: J.C. MacRae
        Vice President/Chief Financial Officer

        10.9 Public Disclosure. Neither party will originate any publicity, news
release or public announcement, written or oral, whether to the public, the
press, public stockholders or otherwise, referring to the subject matter of this
Agreement, the performance under it, or any of its specific terms and
conditions, except such statements or announcements, as in the opinion of the
counsel for the party making such announcement, are required by law, including
United States securities laws, rules or regulations, the U.K. Companies Act
requirements and the listing rules of

                                      -12-
<PAGE>   17

the London Stock Exchange, without the prior written consent of the other party.
If a party decides to make a statement or announcement it believes to be
required by law with respect to this Agreement, it will give the other party
such notice as is reasonably practicable and an opportunity to comment upon the
statement or announcement.

        10.10 Amendment; No Waiver. This Agreement may be amended in a written
amendment signed by both parties hereto. Any waiver by any party hereto of a
breach of any provisions of this Agreement will not be implied and will not be
valid unless such waiver is made in a writing signed by such party. Failure of
any party to require, in one or more instances, performance by the other party
in strict accordance with the terms and conditions of this Agreement will not be
deemed a waiver of the future performance of any such terms or conditions or of
any other terms and conditions of this Agreement. A waiver by either party of
any term or condition of this Agreement will not be deemed or construed to be a
waiver of such term or condition or any other term or condition. All rights,
remedies, undertakings, obligations and agreements contained in this Agreement
will be cumulative and none of them will be a limitation of any other remedy,
right, undertaking, obligation or agreement of either party.

        10.11 No Conflict. Each party represents that neither this Agreement nor
any of its obligations hereunder will conflict or result in a breach of any
arrangement or agreement between such party and any third party. Each party
represents that it has not been debarred and has not been the subject of
debarment proceedings by the FDA or any other regulatory authority. Each party
will undertake the activities to be undertaken by it pursuant to this Agreement
in compliance with applicable laws.

        10.12 Governing Law. This Agreement will be governed by the laws of the
State of California, excluding any choice of law rules which may direct the
application of the laws of another jurisdiction.

        10.13 No Strict Construction. This Agreement has been prepared jointly
by the parties and shall not be strictly construed against either party.

        10.14 Counterparts. This Agreement may be executed in two counterparts,
both of which, taken together, shall constitute the full agreement of the
parties.

                                      -13-
<PAGE>   18

        IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed in duplicate as of the date and year first above written by their
respective duly authorized representatives.

BIOZYME LABORATORIES, LTD.                   ADVANCED CORNEAL SYSTEMS, INC.

By:  /s/ [ILLEGIBLE]                         By:   /s/ [ILLEGIBLE]
     ------------------------------                -----------------------------

Title: Managing Director                     Title: Vice President
      -----------------------------                -----------------------------

                                      -14-
<PAGE>   19

        Exhibit A - Specifications

        Exhibit B - Equipment

        Exhibit C - Testing Specifications

        Exhibit D - Stability Testing

<PAGE>   20

                                    EXHIBIT A

                                 Specifications

GENERAL:

White fluffy powder with no less than 7,000 I.U./mg hyaluronidase activity
sourced from ovine testes. Other product specifications as per Release Testing
Specifications as contained in EXHIBIT C.

PACKAGING AND STORAGE:

Package in airtight polycarbonate containers and store frozen (<-15(degrees)C).

LABELING:

Primary package must be labeled with ACS name, full product name, product code
#, lot #, weight, contents, storage condition, and retest date.

SHIPPING:

Insure primary package is well insolated. Seal insolated container in a sturdy
corrugated box. Ship by commercial air courier only. Enclose certificate of
analysis with shipment.

                                      D-1
<PAGE>   21

                                    EXHIBIT B

                                    Equipment

<TABLE>
<CAPTION>
                                                      Estimated Cost

Description                                           (in British Pounds)
-----------                                           -------------------
<S>                                                   <C>

15 Liter Ion Exchange Column                          2,600 Pound Sterling

Ion Exchange Resin for 15 Liter Column                2,900 Pound Sterling

Freeze Drying Apparatus (Lyophilizer)                 11,500 Pound Sterling

Plastic Ware, (buckets, bins, etc.), Beakers          1,400 Pound Sterling

Millipore Purified Water System
Equipment/Installation                                Not to Exceed 17,300 Pound Sterling

Total Organic Carbon Analyzer                         Not to Exceed 9,998 Pound Sterling

300L Ion Exchange Column                              27,500 Pound Sterling

Ion Exchange Resin for 300 Liter Column               6,000 Pound Sterling

UF Membranes                                          1,900 Pound Sterling

Lyophilization Flasks                                 1,200 Pound Sterling

Dry Box with balance                                  5,000 Pound Sterling

Glassware, bins                                       Not to Exceed 1,000 Pound Sterling
</TABLE>

                                      D-2
<PAGE>   22

                                    EXHIBIT C

                             Testing Specifications

                        In Process Testing Specification*

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------

In-Process Test                              Specification
--------------------------------------------------------------------------------
<S>                                          <C>

I.U./E280 of Combined "A" Fraction           No less than 10,000
--------------------------------------------------------------------------------
</TABLE>

*Additional in-process specification as applied to HY06 process; all other
in-process specification will apply.

                         Release Testing Specifications

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------

Release Test                                 Specification
----------------------------------------------------------------------------------------
<S>                                          <C>
Assay (hyaluronidase activity)               No less than 7,000 I.U./mg

Physical Appearance                          White fluffy powder

Solubility and Appearance of Solution        Dissolves readily at 5 mg/mL in
                                             0.02M sodium phosphate/0.45%
                                             sodium chloride/0.01% bovine serum
                                             albumin, pH 6.9, to give a clear
                                             colorless solution.

pH (30 mg in 10mL water)                     4.5 to 7.5

Loss on Drying, or Water by Karl Fischer     To be determined following process
                                             development

Bacterial Endotoxins                         No more than 0.2 I.U. endotoxin per I.U.
                                             hyaluronidase

Microbial Limit Tests                        No E. coli, S. aureus, P. aeruginosa, or
                                             Salmonella contamination.  Total
                                             microbial contamination less than 1000
                                             organisms per gram hyaluronidase.

SDS-PAGE                                     To be determined following process
                                             development work using newly
                                             received ovine testes.
----------------------------------------------------------------------------------------
</TABLE>

                                      D-3
<PAGE>   23

                                    EXHIBIT D

                                Stability Testing

Stability testing must be conducted on all validation batches, the first three
batches produced post regulatory approval and on a minimum of one batch per year
following regulatory approval.

The containers to be used in stability evaluations should be the same as the
actual packaging used for storage and distribution.

STABILITY TESTING TEMPERATURES AND DURATIONS:

Test all stability batches at freezer (between -25 degrees C and -10 degrees C)
and refrigerated (between 2 degrees C and 8 degrees C) conditions. Freezer and
refrigerated samples should be tested for a minimum of 3 years.

STABILITY TESTING INTERVALS:

Test stability batch samples every 3 months over the first year, every 6 months
over the second year, and then annually.

                        Stability Testing Specifications

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------

Release Test                            Specification
--------------------------------------------------------------------------------
<S>                                     <C>

Assay (hyaluronidase activity)          No less than 7,000 I.U./mg

Physical Appearance                     White fluffy powder

Solubility and Appearance of Solution   Dissolves readily at 5 mg/mL in
                                        0.02M sodium phosphate/0.45%
                                        sodium chloride/0.01% bovine serum
                                        albumin, pH 6.9, to give a clear
                                        colorless solution.

pH (30 mg in 10mL water)                4.5 to 7.5
--------------------------------------------------------------------------------
</TABLE>

                                      D-4<PAGE>   1
                                                                   EXHIBIT 10.18

================================================================================

                           ISTA PHARMACEUTICALS, INC.

                  SERIES D PREFERRED STOCK PURCHASE AGREEMENT

                              Dated March 29, 2000

================================================================================

<PAGE>   2

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                                 PAGE
                                                                                                                 ----
<S>            <C>                                                                                               <C>
1.             Purchase and Sale of Stock..........................................................................1

               1.1           Sale and Issuance of Series D Preferred Stock.........................................1
               1.2           Closing Date; Delivery................................................................1

2.             Representations and Warranties of the Company.......................................................1

               2.1           Organization, Good Standing and Qualification.........................................2
               2.2           Capitalization........................................................................2
               2.3           Subsidiaries..........................................................................2
               2.4           Authorization.........................................................................3
               2.5           Valid Issuance of Preferred and Common Stock..........................................3
               2.6           Governmental Consents.................................................................3
               2.7           Litigation............................................................................3
               2.8           Confidential Disclosure Agreement.....................................................4
               2.9           Patents and Trademarks................................................................4
               2.10          Compliance with Other Instruments.....................................................4
               2.11          Agreements; Action....................................................................5
               2.12          Financial Statements..................................................................6
               2.13          Disclosure............................................................................6
               2.14          Registration Rights...................................................................6
               2.15          Corporate Documents...................................................................6
               2.16          Title to Property and Assets..........................................................6
               2.17          Employee Benefit Plans................................................................6
               2.18          Tax Returns, Payments and Elections...................................................7
               2.19          Labor Agreements and Actions..........................................................7
               2.20          Environmental and Safety Laws.........................................................7
               2.21          Real Property Holding Corporation.....................................................7
               2.22          Insurance.............................................................................7
               2.23          Year 2000.............................................................................7

3.             Representations and Warranties of the Investor......................................................8

               3.1           Authorization.........................................................................8
               3.2           Purchase Entirely for Own Account.....................................................8
               3.3           Disclosure of Information.............................................................8
               3.4           Investment Experience.................................................................8
               3.5           Restricted Securities.................................................................8
               3.6           Further Limitations on Disposition....................................................9
               3.7           Legends...............................................................................9

4.             California Commissioner of Corporations.............................................................9
</TABLE>

                                      -i-

<PAGE>   3

                                TABLE OF CONTENTS
                                   (CONTINUED)

<TABLE>
<S>            <C>                                                                                               <C>
5.             Conditions to Investors' Obligations at Closing....................................................10

               5.1           Representations and Warranties.......................................................10
               5.2           Performance..........................................................................10
               5.3           Compliance Certificate...............................................................10
               5.4           Qualifications.......................................................................10
               5.5           Opinion of Company Counsel...........................................................10
               5.6           Investors Rights Agreement...........................................................10
               5.7           Election of Director.................................................................10

6.             Conditions of the Company's Obligations at Closing.................................................10

               6.1           Representations and Warranties.......................................................11
               6.2           Payment of Purchase Price............................................................11
               6.3           California Qualification.............................................................11
               6.4           Articles.............................................................................11
               6.5           Investors Rights Agreement...........................................................11

7.             Covenants..........................................................................................11

               7.1           First Refusal and Co-Sale Agreement..................................................11
               7.2           Board of Directors...................................................................11

8.             Miscellaneous......................................................................................11

               8.1           Survival of Warranties...............................................................11
               8.2           Successors and Assigns...............................................................11
               8.3           Governing Law........................................................................12
               8.4           Counterparts.........................................................................12
               8.5           Titles and Subtitles.................................................................12
               8.6           Notices..............................................................................12
               8.7           Finder's Fee.........................................................................12
               8.8           Expenses.............................................................................12
               8.9           Amendments and Waivers...............................................................12
               8.10          Severability.........................................................................13
</TABLE>

EXHIBITS

A              Schedule of Investors
B              Amended and Restated Articles of Incorporation
C              Schedule of Exceptions
D              Amended and Restated Investors Rights Agreement
E              Wilson Sonsini Goodrich & Rosati Legal Opinion
F              First Refusal and Co-Sale Agreement

                                      -ii-

<PAGE>   4

                   SERIES D PREFERRED STOCK PURCHASE AGREEMENT

        THIS SERIES D PREFERRED STOCK PURCHASE AGREEMENT is made as of the 29th
day of March, by and between Ista Pharmaceuticals, Inc., a California
corporation located at 15279 Alton Parkway, Suite 100, Irvine, California 92618
(the "Company"), and the investors listed on Exhibit A hereto, each of which is
herein referred to as an "Investor."

        THE PARTIES HEREBY AGREE AS FOLLOWS:

        1. Purchase and Sale of Stock.

           1.1 Sale and Issuance of Series D Preferred Stock.

               (a) The Company has authorized the sale and issuance of up to
1,776,199 shares of its Series D Preferred Stock (the "Shares") having the
rights, privileges and preferences as set forth in the Company's Amended and
Restated Articles of Incorporation (the "Articles") in the form attached to this
Agreement as Exhibit B.

               (b) Subject to the terms and conditions of this Agreement, the
Company will severally issue and sell to each of the Investors, and the
Investors will severally buy from the Company the total number of Shares set
forth opposite such Investor's name on Exhibit A for the purchase price equal to
$5.63 times the number of Shares being purchased. The Company's agreements with
each Investor are separate agreements, and the sale to each Investor is a
separate sale.

           1.2 Closing Date; Delivery.

               (a) Closing. The closing of the purchase and sale of the Shares
under this Agreement to the Investors shall be held at 10:00 a.m. on March 29,
at the offices of Wilson Sonsini Goodrich & Rosati, 650 Page Mill Road, Palo
Alto, California 94304-1050 or at such other time and place as the Company and
the Investors may agree (the "Closing"). The date of such closing is hereinafter
referred to as the "Closing Date."

               (b) At the Closing (as defined below) the Company shall deliver
to each Investor a certificate, registered in such Investor's name, representing
the number of Shares to be purchased by such Investor at the Closing as
specified in Exhibit A, against payment of the purchase price therefor by check
payable to the Company or by wire transfer in accordance with the Company's
wiring instructions.

        2. Representations and Warranties of the Company. The Company hereby
represents and warrants to each Investor that, except as set forth on a Schedule
of Exceptions attached hereto as

<PAGE>   5

Exhibit C, which exceptions shall be deemed to be representations and warranties
as if made hereunder:

           2.1 Organization, Good Standing and Qualification. The Company is a
corporation duly organized, validly existing and in good standing under the laws
of the State of California and has all requisite corporate power and authority
to execute and deliver this Agreement, and the agreements set forth as Exhibits
hereto (collectively, the "Agreements"), to issue, transfer, and sell the Shares
hereunder, to issue the Common Stock issuable upon conversion of the Shares, and
to carry out and perform its obligations under the terms of the Agreements. The
Company is duly qualified to transact business and is in good standing in each
jurisdiction in which the failure so to qualify would have a material adverse
effect on its business or properties.

           2.2 Capitalization. The authorized capital of the Company consists,
or will consist prior to the Closing, of:

               (a) 26,933,878 shares of Preferred Stock (the "Preferred Stock"),
of which 1,951,753 shares have been designated Series A Preferred Stock,
1,951,753 shares have been designated Series A-1 Preferred Stock, 1,955,555
shares have been designated Series B Preferred Stock, 1,955,555 shares have been
designated Series B-1 Preferred Stock, 6,600,000 shares have been designated
Series C Preferred Stock, 6,600,000 shares have been designated Series C-1
Preferred Stock, 2,959,631 shares have been designated Series D Preferred Stock
and 2,959,631 shares have been designated Series D-1 Preferred Stock. Prior to
the Closing, 1,951,753 shares of Series A Preferred Stock are outstanding,
1,955,555 shares of Series B Preferred Stock are outstanding and 6,568,269
shares of Series C Preferred Stock are outstanding, and up to 1,776,199
additional shares of Series D Preferred Stock will be sold pursuant to this
Agreement. The rights, privileges and preferences of the Shares will be as
stated in the Articles attached hereto as Exhibit B.

               (b) 40,000,000 shares of Common Stock (the "Common Stock"), of
which 2,438,927 shares are issued and outstanding.

               (c) Except as set forth in the Schedule of Exceptions, there are
no outstanding options, warrants, rights (including conversion or preemptive
rights) or agreements for the purchase or acquisition from the Company of any
shares of its capital stock.

               (d) Except as hereinabove described, (i) the Company has no
shares reserved for issuance, and (ii) all of the outstanding shares have been
duly authorized and are validly issued, fully-paid and nonassessable.

               (e) The Company does not have outstanding any bonds, debentures,
notes or other obligations the holders of which have the right to vote (or
convertible into or exercisable for securities having the right to vote) with
the stockholders of the Company on any matter.

           2.3 Subsidiaries. The Company does not presently own or control,
directly or indirectly, any interest in any other corporation, association, or
other business entity.

                                      -2-
<PAGE>   6

           2.4 Authorization. The Company has all requisite corporate power and
authority to execute, deliver and perform its obligations under this Agreement.
All corporate action on the part of the Company, its officers, directors and
shareholders necessary for the authorization, execution and delivery of the
Agreements, the performance of all obligations of the Company hereunder and the
authorization, issuance and delivery of the Shares being sold and transferred
hereunder and the Common Stock issuable upon conversion of the Shares have been
taken or will be taken prior to the Closing, and the Agreements constitute valid
and legally binding obligations of the Company, enforceable in accordance with
their terms.

           2.5 Valid Issuance of Preferred and Common Stock.

               (a) The Shares which are being transferred to the Investors
hereunder, when issued, sold and delivered in accordance with the terms hereof
for the consideration expressed herein, will be duly and validly issued, fully
paid and nonassessable and, based in part upon the representations of the
Investors in this Agreement, will be issued in compliance with all applicable
federal and state securities laws. The Common Stock issuable upon conversion of
the Shares have been duly and validly reserved for issuance and, upon issuance
in accordance with the provisions of this Agreement, shall be duly and validly
issued, fully paid and nonassessable, free of any liens or encumbrances, and
issued in compliance with all applicable federal and state securities law. The
transfer of the Shares offered hereby and the subsequent conversion of the
Shares into Common Stock are not and will not be subject to any preemptive
rights or rights of first refusal that have not been properly waived or complied
with.

               (b) The outstanding shares of Common Stock and Preferred Stock
are all duly and validly authorized and issued, fully paid and nonassessable,
and were issued in compliance with all applicable federal and state securities
laws and all preemptive rights and rights of first refusal.

           2.6 Governmental Consents. No consent, approval, order or
authorization of, or registration, qualification, designation, declaration or
filing with, any federal, state, local or provincial governmental authority on
the part of the Company is required in connection with the consummation of the
transactions contemplated by this Agreement, except for the filing pursuant to
Section 25102(f) of the California Corporate Securities Law of 1968, as amended,
and the rules thereunder, which filing will be effected within 15 days of the
transfer of the Shares, and any other filing required by applicable state
securities or blue sky laws, which will be filed in a timely manner.

           2.7 Litigation. There is no action, suit, proceeding or investigation
pending or, to the knowledge of the Company, currently threatened against the
Company which questions the validity of this Agreement or the right of the
Company to enter into it, or to consummate the transactions contemplated hereby,
or which might result, either individually or in the aggregate, in any material
adverse changes in the assets, condition, affairs or prospects of the Company,
financially or otherwise, or any change in the current equity ownership of the
Company, nor is the Company aware that there is any basis for the foregoing. The
foregoing includes, without limitation, actions pending or threatened (or any
basis therefor known to the Company) involving the prior employment of any of
the Company's employees, their use in connection with the Company's business of
any information or techniques allegedly proprietary to any of their former
employers, or their obligations

                                      -3-
<PAGE>   7

under any agreements with prior employers. The Company is not a party or subject
to the provisions of any order, writ, injunction, judgment or decree of any
court or government agency or instrumentality. There is no action, suit,
proceeding or investigation by the Company currently pending or which the
Company intends to initiate.

           2.8 Confidential Disclosure Agreement. Each employee, consultant and
officer of the Company has executed a Confidential Disclosure Agreement similar
to the form attached hereto as Exhibit D and no exceptions have been taken by
any such employee, consultant or officer to the terms of such agreement. The
Company, after reasonable investigation, is not aware that any of its employees
or consultants are in violation thereof, and the Company will use its best
efforts to prevent any such violation.

           2.9 Patents and Trademarks. The Company has sufficient title and
ownership of all patents, trademarks, service marks, trade names, copyrights,
trade secrets, knowhow information, proprietary rights and processes necessary
for its business as now conducted and as proposed to be conducted and to the
best of its knowledge without any conflict with or infringement of the rights of
others. There are no outstanding options, licenses, or agreements of any kind
relating to the foregoing, nor is the Company bound by or a party to any
options, licenses or agreements of any kind with respect to the patents,
trademarks, service marks, trade names, copyrights, trade secrets, licenses,
information, proprietary rights and processes of any other person or entity. The
Company has not received any communications alleging that the Company has
violated or, by conducting its business as proposed, would violate any of the
patents, trademarks, service marks, trade names, copyrights or trade secrets or
other proprietary rights of any other person or entity. The Company is not aware
of any reasonable basis for the denial of any pending patent application
(including divisions, continuations, continuations in part and renewal
applications) relating to the Company's intellectual property rights. The
Company is not aware that any of its employees, consultants and officers is
obligated under any contract (including licenses, covenants or commitments of
any nature) or other agreement, or subject to any judgment, decree or order of
any court or administrative agency, that would interfere with the use of his
best efforts to promote the interests of the Company or that would conflict with
the Company's business as proposed to be conducted. Neither the execution,
delivery nor performance of this Agreement, nor the carrying on of the Company's
business by the employees, consultants or officers of the Company, nor the
conduct of the Company's business as proposed, will, to the Company's knowledge,
conflict with or result in a breach of the terms, conditions or provisions of,
or constitute a default under, any contract, covenant or instrument under which
any of such employees, consultants or officers is now obligated.

           2.10 Compliance with Other Instruments.

               (a) The Company is not in violation or default of any provisions
of its Articles or Bylaws or of any instrument, judgment, order, writ, decree or
contract to which it is a party or by which it is bound or, to its knowledge, of
any provision of federal or state statute, rule or regulation applicable to the
Company. The execution, delivery and performance of this Agreement and the
consummation of the transactions contemplated hereby will not result in any such
violation or be in conflict with or constitute, with or without the passage of
time and giving of notice, either a default

                                      -4-
<PAGE>   8

under any such provision, instrument, judgment, order, writ, decree or contract
or an event which results in the creation of any lien, charge or encumbrance
upon any assets of the Company. The business of the Company is not being,
conducted in violation of any federal, state, local or foreign law, statute,
ordinance, rule, regulation, judgment, order, injunction, decree, arbitration
awarded, agency requirements, license or permit of any governmental entity
(collectively "Laws"). No investigation or review by any governmental entity
with respect to the Company is pending or, to the knowledge of the Company,
threatened, nor has any governmental entity indicated an intention to conduct
the same. To the knowledge of the Company, no material change is required in the
Company's processes, properties or procedures in connection with any such Laws
and the Company has not received any notice or communication of any material
noncompliance with any such Laws that has not been cured as of the date hereof.
The Company has all permits, licenses, franchises, variances, exemption, orders
and other governmental authorizations, consent and approvals necessary to
conduct its business as presently conducted except those the absence of which
are not, individually or in the aggregate, reasonably likely to have a material
adverse effect or prevent or materially burden or materially impair the ability
of the Company to operate its business.

               (b) The Company has avoided every condition, and has not
performed any act, the occurrence of which would result in the Company's loss of
any right granted under any license, distribution or other agreement.

           2.11 Agreements; Action.

                (a) Except for agreements explicitly contemplated hereby, there
are no agreements, understandings or proposed transactions between the Company
and any of its officers, directors, affiliates, or any affiliate thereof.

                (b) There are no agreements, understandings, instruments,
contracts or proposed transactions to which the Company is a party or by which
it is bound which involve (i) obligations of, or payments to the Company in
excess of $15,000, or (ii) the license of any patent, copyright, trade secret or
other proprietary right to or from the Company.

                (c) The Company has not (i) declared or paid any dividends, or
authorized or made any distribution upon or with respect to any class or Series
of its capital stock, (ii) incurred any indebtedness for money borrowed or
incurred any other liabilities individually in excess of $15,000 or in excess of
$25,000 in the aggregate, (iii) made any loans or advances to any person, other
than ordinary advances for travel expenses, or (iv) sold, exchanged or otherwise
disposed of any of its assets or rights, other than in the ordinary course of
business.

                (d) The Company is not a party to and is not bound by any
contract, agreement or instrument, or subject to any restriction under its
Articles or Bylaws, which materially adversely affects its business as now
conducted and as proposed to be conducted.

                (e) The Company has not engaged in the past twelve (12) months
in any discussion (i) with any representative of any corporation or corporations
regarding the consolidation or merger of the Company with or into any such
corporation or corporations, (ii) with any

                                      -5-
<PAGE>   9

corporation, partnership, association or other business entity or any individual
regarding the sale, conveyance or disposition of all or substantially all of the
assets of the Company or a transaction or Series of related transactions in
which more than fifty percent (50%) of the voting power of the Company is
disposed of, or (iii) regarding any other form of acquisition, liquidation,
dissolution or winding up of the Company.

           2.12 Financial Statements. The Company has furnished to each Investor
its unaudited balance sheet as of December 31, 1999 (the "Balance Sheet") and
income statement for the period ended December 31, 1999 (collectively, the
"Financial Statements"). The Financial Statements, together with the notes
thereto, (i) are complete and correct in all material respects, (ii) are in
accordance with the Company's books and records, (iii) present fairly its
financial position as of that date and the results of its operations for the
period indicated, and (iv) have been prepared in conformity with generally
accepted accounting principles consistently applied throughout the periods
indicated, subject in the case of interim statements to year end adjustments and
the absence of footnotes. Since December 31, 1999 (i) there has been no material
adverse change in the financial condition, results of operations, business,
properties or prospects of the Company, and (ii) the Company has conducted its
business only in, and has not engaged in any material transaction other than
according to, the ordinary and usual course of its business.

           2.13 Disclosure. The Company has fully provided each Investor with
all the information which such Investor has requested for deciding whether to
purchase the Shares and all information which the Company believes is reasonably
necessary to enable such Investor to make such decision. Neither the Agreements
nor any other statements or certificates made or delivered in connection
herewith contains any untrue statement of a material fact or omits to state a
material fact necessary to make the statements herein or therein not misleading.

           2.14 Registration Rights. Except as provided in the Investors Rights
Agreement attached hereto as Exhibit E of this Agreement, the Company has not
granted or agreed to grant any registration rights, including piggyback rights,
to any person or entity.

           2.15 Corporate Documents. Except for amendments necessary to satisfy
representations and warranties or conditions contained herein (the form of which
amendments has been approved by the Investors), the Articles and Bylaws of the
Company are in the form previously provided to the Investors.

           2.16 Title to Property and Assets. The Company owns its property and
assets free and clear of all mortgages, liens, loans and encumbrances, except
such encumbrances and liens which arise in the ordinary course of business and
do not materially impair the Company's ownership or use of such property or
assets. With respect to the property and assets it leases, the Company is in
compliance with such leases and, to its knowledge, holds a valid leasehold
interest free of any liens, claims or encumbrances.

           2.17 Employee Benefit Plans. The Company does not have any Employee
Benefit Plan as defined in the Employee Retirement Income Security Act of 1974.

                                      -6-
<PAGE>   10

           2.18 Tax Returns, Payments and Elections. The Company has filed all
tax returns and reports as required by law. These returns and reports are true
and correct in all material respects. The Company has paid all taxes and other
assessments due, except those contested by it in good faith which are listed in
the Schedule of Exceptions. As of the date hereof, there are not pending or, to
the knowledge of the Company threatened in writing, any audits, examinations,
investigations or other proceedings against the Company in respect to taxes or
tax matters. There are not any unresolved questions or claims concerning the
Company's tax liability that may have a material adverse effect on the Company.
The provision for taxes of the Company as shown in the Balance Sheet is adequate
for taxes due or accrued as of the date thereof. The Company has not elected
pursuant to the Internal Revenue Code of 1986, as amended (the "Code"), to be
treated as a Subchapter S corporation or a collapsible corporation pursuant to
Section 341(f) or Section 1362(a) of the Code, nor has it made any other
elections pursuant to the Code (other than elections which relate solely to
methods of accounting, depreciation or amortization) which would have a material
adverse effect on the financial condition, results of operations, business,
properties or prospects at the Company.

           2.19 Labor Agreements and Actions. The Company is not bound by or
subject to (and none of its assets or properties is bound by or subject to) any
written or oral, express or implied, contract, commitment or arrangement with
any labor union, and no labor union has requested or, to the knowledge of the
Company, has sought to represent any of the employees, representatives or agents
of the Company. There is no strike or other labor dispute involving the Company
pending, or to the knowledge of the Company threatened, which could have a
material adverse effect on the financial condition, results of operations,
business properties or prospects of the Company, nor is the Company aware of any
labor organization activity involving its employees. The Company is not aware
that any officer or key employee, or that any group of key employees, intends to
terminate their employment with the Company, nor does the Company have a present
intention to terminate the employment of any of the foregoing. The employment of
each officer and employee of the Company is terminable at the will of the
Company.

           2.20 Environmental and Safety Laws. To its knowledge, the Company is
not in violation of any applicable statute, law or regulation relating to the
environment or occupational health and safety, and to its knowledge, no material
expenditures are or will be required in order to comply with any such existing
statute, law or regulation.

           2.21 Real Property Holding Corporation. The Company is not a real
property holding corporation within the meaning of Internal Revenue Code Section
897(c)(2) and any regulations promulgated thereunder.

           2.22 Insurance. All material property, clinical trials liability and
general liability insurance policies maintained by the Company are with
reputable insurance carriers, provide adequate coverage for all normal risks
incident to the business of the Company and its properties and assets.

           2.23 Year 2000. The Company has reviewed its operations those of any
third party with which the Company has a material relationship to evaluate the
extent to which the business or operations of the Company will be affected by
the Year 2000 Problem, as defined below. The Year

                                      -7-
<PAGE>   11
2000 Problem is not reasonably likely to have a material adverse effect on the
general affairs, management, the current or future consolidated financial
position, business prospects, stockholders' equity or results of operations of
the Company or result in any material loss or interference with the Company's
business or operations. The "Year 2000 Problem" as used herein, means any
significant risk that the computer hardware or software used in the receipt,
transmission, processing, manipulation, storage, retrieval, retransmission or
other utilization of data or in the operation of mechanical or electrical
systems of any kind will not, in the case of dates or time periods occurring
after December 31, 1999, function at least as effectively as in the case of
dates or time periods occurring prior to January 1, 2000

        3. Representations and Warranties of the Investor. Each Investor hereby
represents and warrants, severally and not jointly, that:

           3.1 Authorization. This Agreement constitutes its valid and legally
binding obligation, enforceable in accordance with its terms.

           3.2 Purchase Entirely for Own Account. This Agreement is made with
each Investor in reliance upon such Investor's representation to the Company,
which by such Investor's execution of this Agreement such Investor hereby
confirms, that the Shares and the Common Stock issuable upon conversion of the
Shares (collectively, the "Securities") will be acquired for investment for such
Investor's own account, not as a nominee or agent (other than those Investors
set forth on the signature page set forth hereto who are acquiring such shares
as custodian or trustee), and not with a view to the resale or distribution of
any part thereof, and that such Investor has no present intention of selling,
granting any participation in, or otherwise distributing the same. By executing
this Agreement, each Investor further represents that such Investor does not
have any contract, undertaking, agreement or arrangement with any person to
sell, transfer or grant participation to such person or to any third person,
with respect to any of the Securities. Each Investor represents that it has full
power and authority to enter into this Agreement.

           3.3 Disclosure of Information. It believes it has received all the
information it considers necessary or appropriate for deciding whether to
purchase the Securities. Each Investor further represents that it has had an
opportunity to ask questions and receive answers from the Company regarding the
terms and conditions of the offering of the Securities. The foregoing, however,
does not limit or modify the representations and warranties of the Company in
Section 2 of this Agreement or the right of the Investors to rely thereon.

           3.4 Investment Experience. Each Investor is an investor in securities
of companies in the development stage and acknowledges that it is able to fend
for itself, and bear the economic risk of its investment and has such knowledge
and experience in financial or business matters that it is capable of evaluating
the merits and risks of the investment in the Securities. If other than an
individual, Investor also represents it has not been organized for the purpose
of acquiring the Securities.

           3.5 Restricted Securities. It understands that the Securities are
characterized as "restricted securities" under the federal securities laws
inasmuch as they are being acquired from the

                                      -8-
<PAGE>   12

Company in a transaction not involving a public offering and that under such
laws and applicable regulations such securities may be resold without
registration under the Securities Act of 1933, as amended (the "Act") only in
certain limited circumstances. In this connection, each Investor represents that
it is familiar with Rule 144, as presently in effect, and understands the resale
limitations imposed thereby and by the Act.

           3.6 Further Limitations on Disposition. Without in any way limiting
the representations set forth above, each Investor further agrees not to make
any disposition of all or any portion of the Securities unless and until:

               (a) There is then in effect a registration statement under the
Act covering such proposed disposition and such disposition is made in
accordance with such registration statement; or

               (b) (i) Such Investor shall have notified the Company of the
proposed disposition and shall have furnished the Company with a detailed
statement of the circumstances surrounding the proposed disposition, and (ii) if
reasonably requested by the Company, such Investor shall have furnished the
Company with an opinion of counsel, reasonably satisfactory to the Company, that
such disposition will not require registration of such shares under the Act. It
is agreed that the Company will not require opinions of counsel for transactions
made pursuant to Rule 144 except in unusual circumstances.

               (c) Notwithstanding the provisions of paragraphs (a) and (b)
above, no such registration statement or opinion of counsel shall be necessary
for a transfer by an Investor which is a partnership to a partner of such
partnership or a retired partner of such partnership who retires after the date
hereof, or to the estate of any such partner or retired partner or the transfer
by gift, will or intestate succession of any partner to his spouse or lineal
descendants or ancestors, if the transferee agrees in writing to be subject to
the terms hereof to the same extent as if he were an original Investor
hereunder.

           3.7 Legends. It is understood that the certificates evidencing the
Securities may bear one or all of the following legends:

               (a) "THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR
HYPOTHECATED IN THE ABSENCE OF A REGISTRATION STATEMENT IN EFFECT WITH RESPECT
TO THE SECURITIES UNDER SUCH ACT OR AN OPINION OF COUNSEL SATISFACTORY TO THE
COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED OR UNLESS SOLD PURSUANT TO RULE
144 OF SUCH ACT."

               (b) Any legend required by the laws of the State of California or
any other applicable state, including any legend required by the California
Department of Corporations and Sections 417 and 418 of the California
Corporations Code.

        4. California Commissioner of Corporations. THE SALE OF THE SECURITIES
THAT IS THE SUBJECT OF THIS AGREEMENT HAS NOT BEEN QUALIFIED WITH THE

                                      -9-
<PAGE>   13

COMMISSIONER OF CORPORATIONS OF THE STATE OF CALIFORNIA, AND THE ISSUANCE OF
SUCH SECURITIES OR THE PAYMENT OR RECEIPT OF ANY PART OF THE CONSIDERATION
THEREFOR PRIOR TO SUCH QUALIFICATION IS UNLAWFUL UNLESS THE SALE OF THE
SECURITIES IS EXEMPT FROM QUALIFICATION BY 25100, 25102 OR 25105 OF THE
CALIFORNIA CORPORATIONS CODE. THE RIGHTS OF ALL PARTIES TO THIS AGREEMENT ARE
EXPRESSLY CONDITIONED UPON SUCH QUALIFICATION BEING OBTAINED UNLESS THE SALE IS
SO EXEMPT.

        5. Conditions to Investors' Obligations at Closing. The obligations of
each Investor under subsection 1.1(b) of this Agreement are subject to the
fulfillment on or before the Closing of each of the following conditions, the
waiver of which shall not be effective against any Investor who does not consent
in writing thereto:

           5.1 Representations and Warranties. The representations and
warranties of the Company contained in Section 2 shall be true on and as of the
Closing with the same effect as though such representations and warranties had
been made on and as of the date of such Closing

           5.2 Performance. The Company shall have performed and complied with
all agreements, obligations and conditions contained in this Agreement that are
required to be performed or complied with by it on or before the Closing.

           5.3 Compliance Certificate. The vice president of the Company shall
deliver to each Investor at the Closing a certificate certifying that the
conditions specified in Sections 5.1 and 5.2 have been fulfilled and stating
that there shall have been no adverse change in the business, affairs,
prospects, operations, properties, assets or condition of the Company since
October 31, 1999.

           5.4 Qualifications. The Commissioner of Corporations of the State of
California shall have issued a permit qualifying the offer and sale of the
Securities to the Investors pursuant to this Agreement, or such offer and sale
shall be exempt from such qualification under the California Corporate
Securities Law of 1968, as amended.

           5.5 Opinion of Company Counsel. Each Investor shall have received
from Wilson Sonsini Goodrich & Rosati, counsel for the Company, an opinion,
dated as of the Closing Date, in the form attached as Exhibit F.

           5.6 Investors Rights Agreement. The Company shall have entered into
the Investors Rights Agreement in the form attached hereto as Exhibit E.

           5.7 Election of Director. Effective upon the Closing, a designee of
Allergan Pharmaceuticals (Ireland) Ltd., Inc., or its affiliate ("Allergan"),
shall be elected to the Company's Board of Directors.

        6. Conditions of the Company's Obligations at Closing. The obligations
of the Company to each Investor under this Agreement are subject to the
fulfillment on or before the Closing of each of

                                      -10-
<PAGE>   14

the following conditions, the waiver of which shall not be effective unless
consented to in writing by the Company:

           6.1 Representations and Warranties. The representations and
warranties of each Investor contained in Section 3 shall be true on and as of
the Closing with the same effect as though such representations and warranties
had been made on and as of the Closing Date.

           6.2 Payment of Purchase Price. The Investors shall have delivered the
purchase price for the Shares.

           6.3 California Qualification. The Commissioner of Corporations of the
State of California shall have issued a permit qualifying the offer and sale to
the Investors of the Securities or such offer and sale shall be exempt from such
qualification under the California Corporate Securities Law of 1968, as amended.

           6.4 Articles. The Articles attached hereto as Exhibit B shall have
been accepted for filing by the California Secretary of State.

           6.5 Investors Rights Agreement. Each Investor shall have entered into
the Investors Rights Agreement in the form attached hereto as Exhibit E.

        7. Covenants.

           7.1 First Refusal and Co-Sale Agreement. The Company will use
commercial best efforts to add each Investor as a party to the First Refusal and
Co-Sale Agreement, in the form attached hereto as Exhibit G.

           7.2 Board of Directors. So long as Allergan owns at least 750,000
Shares or Common Stock of the Company (subject to adjustment for stock splits,
dividends or the like), the Company agrees (i) to nominate a representative of
Allergan to the Company's Board of Directors or (ii) if a nominee of Allergan is
not represented on the Company's Board of Directors, the Company shall invite a
representative of Allergan to attend all meeting of its Board of Directors,
including committee meetings, in a nonvoting observer capacity and, in this
respect, shall give such representative timely copies of all notices, minutes,
consents, and other material that the Company provides to its directors.

        8. Miscellaneous.

           8.1 Survival of Warranties. The warranties, representations and
covenants of the Company and Investors contained in or made pursuant to this
Agreement shall survive the execution and delivery of this Agreement and the
Closing and shall in no way be affected by any investigation of the subject
matter thereof made by or on behalf of the Investors or the Company.

           8.2 Successors and Assigns. The terms and conditions of this
Agreement shall inure to the benefit of and be binding upon the respective
successors and assigns of the parties. Nothing in

                                      -11-
<PAGE>   15

this Agreement, express or implied, is intended to confer upon any party other
than the parties hereto or their respective successors and assigns any rights,
remedies, obligations, or liabilities under or by reason of this Agreement,
except as expressly provided in this Agreement.

           8.3 Governing Law. This Agreement shall be governed by and construed
under the laws of the State of California as applied to agreements among
California residents entered into and to be performed entirely within
California.

           8.4 Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

           8.5 Titles and Subtitles. The titles and subtitles used in this
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

           8.6 Notices. All notices and other communications hereunder shall be
in writing and shall be deemed given (i) upon personal delivery; (ii) upon
transmission by facsimile (receipt verified); (iii) upon the fifth day following
deposit by registered or certified mail (return receipt requested), postage
prepaid, and , if delivered to a party overseas, by air mail; or (iv) upon the
second day following dispatch by express courier service (receipt verified), to
the party to be notified at the address indicated for such party in Exhibit A or
in the case of the Company on the first page of this Agreement, or at such other
address for a party as shall be specified by like notice; provided, that notices
of a change of address shall be effective only upon receipt thereof.

           8.7 Finder's Fee. Each Investor, severally and not jointly, agrees to
indemnify and to hold harmless the Company from any liability for any commission
or compensation in the nature of a finders' fee (and the costs and expenses of
defending against such liability or asserted liability) for which the Investor
or any of its officers, partners, employees, or representatives is responsible.
The Company agrees to indemnify and hold harmless each Investor from any
liability for any commission or compensation in the nature of a finders' fee
(and the costs and expenses of defending against such liability or asserted
liability) for which the Company or any of its officers, employees or
representatives is responsible.

           8.8 Expenses. If any action at law or in equity is necessary to
enforce or interpret the terms of this Agreement or the Articles, the prevailing
party shall be entitled to reasonable attorney's fees, costs and necessary
disbursements in addition to any other relief to which such party may be
entitled.

           8.9 Amendments and Waivers. Any term of this Agreement may be amended
and the observance of any term of this Agreement may be waived (either generally
or in a particular instance and either retroactively or prospectively), only
with the written consent of the Company and the holders of a majority of the
Common Stock issued or issuable upon conversion of the Shares, and with the same
consent the Company may enter into a supplemental agreement for the purpose of
adding any provisions to or changing in any manner or eliminating any of the
provisions of this Agreement. Any amendment or waiver effected in accordance
with this Section 8.9 shall be binding

                                      -12-
<PAGE>   16

upon each holder of any securities purchased under this Agreement at the time
outstanding (including securities into which such securities are convertible),
each future holder of all such securities, and the Company.

           8.10 Severability. If one or more provisions of this Agreement are
held to be unenforceable under applicable law, such provision shall be excluded
from this Agreement and the balance of the Agreement shall be interpreted as if
such provision were so excluded and shall be enforceable in accordance with its
terms.

                [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                      -13-
<PAGE>   17

        IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first above written.

                                           ISTA PHARMACEUTICALS, INC.

                                           By: /s/ EDWARD H. DANSE
                                              ---------------------------------

                                           Title: Chief Executive Officer
                                                 ------------------------------

<PAGE>   18

                                  INVESTORS:

                                  Allergan Pharmaceuticals (Ireland) Ltd., Inc.

                                  By: /s/ FRANCIS R. TUNNEY, JR.
                                     ------------------------------------------

                                  Its: Secretary
                                      -----------------------------------------

<PAGE>   19

                                    EXHIBIT A

                              SCHEDULE OF INVESTORS

<TABLE>
<CAPTION>
                                                            Series D
                                                            Preferred                    Purchase
           Names and Addresses                               Stock                        Price
---------------------------------------------               ---------               -----------------
<S>                                                         <C>                     <C>
Allergan Pharmaceuticals (Ireland) Ltd., Inc.               1,776,199               $   10,000,000.37
2525 Dupont Drive
Irvine, California 92612
</TABLE>

<PAGE>   20

                                    EXHIBIT C

                             SCHEDULE OF EXCEPTIONS

        This Schedule of Exceptions, dated as of March 29, 2000, is made and
given pursuant to paragraph 2 of the Series D Preferred Stock Purchase Agreement
dated March 29, 2000 (the "Agreement") of Ista Pharmaceuticals, Inc. (the
"Company"). The paragraph numbers in this Schedule of Exceptions correspond to
the paragraph numbers in the Agreement; however, any information disclosed
herein under any paragraph number shall be deemed to be disclosed and
incorporated into any other paragraph number under the Agreement where such
disclosure would be appropriate. Any terms defined in the Agreement shall have
the same meaning when used in this Schedule of Exceptions as when used in the
Agreement unless the context otherwise requires.

        2.2 Capitalization.

            (c) The Company has adopted a stock option plan under which
4,750,000 shares of Common Stock have been reserved for issuance. Prior to the
Closing, options to purchase 3,341,050 shares of the Company's Common Stock are
currently outstanding and 728,367 shares of the Company's Common Stock have been
reserved for future grants.

            The Company has entered into an Investors Rights Agreement, dated as
of the date hereto, pursuant to which the holders of at least 100,000 shares of
Preferred Stock have been granted a right of first offer to purchase certain
securities offered by the Company.

            The Company has issued Warrants for the purchase of up to 1,153,777
shares of Common Stock. The Warrants entitle the holder to purchase Common Stock
at a purchase price of $0.56 per share. The Warrants expire at the earlier of a
firmly underwritten public offering of the Company's common stock or five years
from date of issuance.

            The Company and certain shareholders have entered into a First
Refusal and Co-Sale Agreement, dated as of the date hereof.

        2.3 Subsidiaries. The Company owns 100% of the capital stock of Visionex
Pte. Ltd ("Visionex"), a company organized under the laws of Singapore.

        2.5 Valid Issuance of Preferred and Common Stock.

            See Section 2.2 above.

            Investors' subsequent transfers of the Shares may be subject to the
First Refusal and Co-Sale Agreement.

        2.8 Confidential Disclosure Agreement.

            Each of our scientific advisors has signed a non-disclosure
agreement.

<PAGE>   21

        2.9 Patents and Trademarks.

            The Company has entered into a field-limited exclusive license
agreement with a certain third-party pursuant to which the Company may develop
and commercialize certain ophthalmic products utilizing the enzyme
hyaluronidase.

            The Company has entered into a Trademark License Agreement with
Sophia S.A. granting certain rights to Sophia for the use of the Company's
Vitrase mark in Mexico.

            The Company intends to enter into an agreement with Keratoform and
its founders to acquire the rights to certain U.S. and foreign patent
applications.

            The Company intends to enter into an agreement with Allergan Sales,
Inc. and Allergan Sales, Ltd. whereby Allergan Sales, Inc. and Allergan Sales,
Ltd. would be granted certain rights for the use of the Company's Vitrase
related patents.

        2.11 Agreements; Action.

             See 2.9 above.

             (a) The Company entered into unsecured loan agreement, dated
May 29, 1997, with Edward Danse, the Company's Chief Executive Officer.

             (b) The Company has entered into a lease credit line with Lease
Management Services, Inc. pursuant to which the Company granted a security
interest in its fixed assets. Under this agreement, the Company has an
outstanding balance of approximately $300,000 and lease credit line of
$1,100,000.

             The Company has entered into a commercial Lease Agreement, dated
September 13, 1996, for its offices located at 15279 Alton Parkway, Irvine,
California, which provides for monthly lease payments of approximately $12,000
through September 30, 2001.

             The Company has entered into a Commercial Lease agreement, dated
January 1, 1996, for medical offices in Tijuana, Mexico which provides for
monthly lease payments of approximately $3,000 through January, 2003.

             The Company has entered into consulting agreements with the
following individuals; Charles May, O.D. (variable up to $6,000 per month),
Christina Kenney, M.D. Ph.D. ($5,000 per month), David Harper, M.D. ($7,500 per
month), Frank Killey, Ph.D. (approximately $12,000 per month), Edgar Thomas,
M.D. (approximately $7,500 per month), Baruch Kupperman, M.D. Ph.D.
(approximately $7,500 per month), Anthony Nesburn, M.D. ($3,000 per quarter),
Judy Atkins (approximately $10,000 per month) and Syneract, Inc. (approximately
$10,000 per month).

                                      -2-
<PAGE>   22

             The Company intends to enter into an agreement with Staticon, Inc.
which will provide for up to approximately $200,000 in payments for clinical
research services in connection with the Company's Vitrase Phase III Study in
Hungary.

             The Company has entered into a development agreement with ChemSyn
Laboratories which provides for payments of up to $34,500 in connection with the
development of GMP production of a certain raw material used for one of the
Company's products.

             The Company has entered into a Distribution agreement, dated April
23, 1998, with Sophia S.A. which grants Sophia exclusive distribution rights for
the Company's Vitrase product in Mexico.

             The Company has entered into a Distribution Agreement, dated June
27, 1997, with Visionex which grants Visionex exclusive distribution rights for
the Company's Vitrase and Corneaplasty products in certain Asian markets.

             The Company has entered into an agreement with CroMedica Global,
Inc. ("CroMedica"), dated September 8, 1998, which provides for up to $450,000
in payments for clinical research services in connection with the Company's
Vitrase Phase III Study in South Africa.

             The Company has entered into an agreement with Covance dated
November 3, 1998, modified September 10, 1999, which provides for up to
approximately $6 million in payments for clinical research services in
connection with the Company's Vitrase Phase III Studies in the United States,
Canada, Europe and Brazil.

             The Company has entered into an agreement with CroMedica dated May
19, 1999, which provides for payments up to $2.7 million for the performance of
clinical research services in connection with the completion of Company's
Vitrase Phase III Studies in the United States, Canada, South Africa, Australia
and Europe.

             The Company has entered or intends to enter into agreements with
all clinical investigators involved in the Company's Vitrase Phase III clinical
trials, which among other provisions, will provide for payments to the clinical
investigator of up to $3,000 per enrolled patient.

             The Company has entered into a Supply Agreement dated September 23,
1999 with Biozyme Laboratories, Ltd. which, amongst other provisions, will
require the Company to purchase certain capital equipment totaling $140,000,
provide payment to Biozyme of approximately $130,000 upon achievement of certain
events, and require the Company to purchase minimum annual amounts of material
from Biozyme.

             In connection with the terms of the Company's Supply Agreement with
Biozyme Laboratories, Inc., Company is required, beginning in calendar year
1999, to purchase annual minimum amounts of material from Biozyme.

                                      -3-
<PAGE>   23

             On March 9, 2000, the Company borrowed $4,000,000 from Visionex,
its wholly owned subsidiary (the "Note"). The Note, which was provided to
Investor's counsel for review, carries a 7% and is due on January 31, 2001.

        2.16 Title to Property and Assets. The Company has entered into a lease
credit line with Lease Management Services, Inc. pursuant to which the Company
granted a security interest in its fixed assets. Under this agreement, the
Company has an outstanding balance of approximately $300,000 and lease credit
line of $1,100,000.

        2.17 Employee Benefit Plans. The Company has established a
non-contributory 401(k) plan for its employees.

        2.23 Year 2000.

               The Company has completed an assessment of its internal computer
software and hardware systems, and believes that the "Year 2000 Problem" is not
likely to have a material effect on the Company's business or operations
conducted with these systems.

               The Company has reviewed representations of CroMedica and Covance
with regard to its programs regarding the "Year 2000 Problem." CroMedica and
Covance have made representations to the Company that these programs will result
in Year 2000 compliance, however, the Company cannot verify CroMedica's and
Covance's full year 2000 compliance at this time.

               The Company has reviewed the operations of other vendors which
are currently providing services to the Company and does not believe that the
"Year 2000 Problem" will have a material effect on the Company's operations as
it pertains to these vendors.

                [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                      -4-
<PAGE>   24

        IN WITNESS WHEREOF, the Company has caused this Schedule of Exceptions
to be executed by its proper and duly authorized officer as of the date and year
first written above.

                                           ISTA PHARMACEUTICALS, INC.

                                           By:
                                              ---------------------------------

                                           Title:
                                                 ------------------------------

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