<PAGE>   1
                                                                   EXHIBIT 10.13

                             DISTRIBUTOR AGREEMENT




THIS AGREEMENT is entered into and made effective as of this 23rd day of April
of 1998 by ADVANCED CORNEAL SYSTEMS, INC., represented herein by MR. EDWARD H.
DANSE (Hereinafter referred to as the "Company"), and on the other part by
LABORATORIES SOPHIA S.A. DE C.V. represented herein by MR. FERNANDO SANCHEZ
BECERRA (Hereinafter referred to as the "Distributor").

RECITALS

WHEREAS, the Company is in the business of discovering, developing and
commercializing products and technology useful in the treatment and prevention
of irregularities, malformations and diseases of the eye; and

WHEREAS, the Company has developed proprietary technology to clear a vitreous
hemorrhage and desires to have the Distributor market and sell the Product (as
defined on Exhibit A attached); and

WHEREAS, the Distributor has the necessary organization, personnel and
facilities to distribute the products within the Territory, including all
required licenses, authorizations and permits as may be required to carry out
the distribution of the products; and

WHEREAS, the Company desires to market and sell its Product in the Territory,
and Distributor desires to market and sell the Product on behalf of the
Company, on the terms and conditions set forth below.

NOW, THEREFORE, THE COMPANY AND DISTRIBUTOR AGREE AS FOLLOWS:

1.   APPOINTMENTS AND ACCEPTANCE

1.1  Company Hereby appoints Distributor on an exclusive basis to purchase and
resell the Products in the Territory. Distributor accepts this appointment on
the terms and conditions set forth herein.

1.2  The term "Products" shall mean the products, specified by brand name,
manufactured and/or sold by the Company listed on Exhibit A hereto. Company, in
its sole discretion, may from time to time modify or change the design or
specification or any type of Products or discontinue the sale of or instruct
Distributor not to sell any Products in the Territory. In such event, Company
shall use reasonable efforts to provide reasonable advance notice to
Distributor of any such deletion or material change or modification to or
instruction with respect to any Product registered with the Mexican Ministry of
Health so that Distributor may make the appropriate regulatory response to such
action, such as an amendment of the Product's registration or re-registration
of the Product. If any such material change or modification to any Product
causes Distributor to fail to meet its obligations to purchase Minimum Product
Quantities in any Contract Year and this failure is beyond Distributor's
reasonable control, then Company and Distributor agree to negotiate in good
faith an equitable adjustment of such Minimum Product Quantity in consideration
thereof.
<PAGE>   2
1.3  Company here grants to Distributor a right of first negotiation to be the
distributor of any item of New Product (as defined below) in the Territory. In
connection therewith, Company shall not appoint any non-Affiliated third party
as the distributor of any item on New Product until Company has offered such
rights to Distributor in accordance herewith and has given Distributor sixty
(60) days to negotiate with Company a mutually acceptable distribution
agreement with respect to such item of New Product in the Territory. If no such
agreement is consummated within such sixty (60) day period, then Company shall
be free to offer such rights to non-Affiliated third party. Notwithstanding the
above, nothing in this Section 1.3 shall, in any way, be construed as
preventing Company from marketing, selling and distributing any item of New
Product directly, or indirectly through an Affiliate, in the Territory. For the
purposes of this Section 1.3, the term "New Product" shall mean any
pharmaceutical product used in connection therewith which Company intends to
offer for distribution by a non-Affiliated third party in the Territory and
which is not otherwise defined as a "Product" hereunder.

1.4  The term "Affiliate" shall mean any corporation or other entity
controlling, controlled by, or under common control with a party to this
Agreement. For such purpose, "control" shall mean the ownership, directly or
indirectly, or more than 50% of the voting stock of a corporate entity or more
than 50% of the beneficial interest of an entity other than a corporation.

1.5  The term "Territory" shall mean the geographic area defined on Exhibit B
hereto. Distributor shall not re-export the Products from the Territory without
the express written authority of Company.

2.   DIRECT SALES

2.1  During the term of this Agreement and provided Distributor complies with
the terms hereof, Company will not sell directly to customers located in the
Territory any Product included in this Agreement, regardless of whether such
Product is offered by the Company under the same or different brand name than
that indicated on Exhibit A.

3.   BUSINESS OF DISTRIBUTOR

3.1  Distributor is and shall remain an independent contractor. Distributor
agrees that the Company has granted it no authority to act or make any
representations or warranties on behalf of Company. Distributor is at all times
acting for its own account, and at its own expense. Distributor represents to
Company that Distributor has adequate personnel, facilities and other resources
in the Territory from which to sell and distribute the Products. Distributor
shall comply with all applicable laws, statutes, regulations and treaties
relating to the sale and distribution of the Products and the performance of
its duties and obligations hereunder.

4.   TERM

4.1  The term of this Agreement shall be for a period of (three) 3 years,
commencing on the effective date above, and shall thereafter automatically be
renewed for further consecutive periods of (three) 3 years each, unless and
until either party shall give to the other not less than (ninety) 90 days prior
written notice of termination before the end of the first or any subsequent
such period.

5.   PRICES AND TERMS

5.1  The prices which Distributor shall pay to Company for the Products shall
be as specified on the Price List included within Exhibit B. The prices quoted
are exclusive of any national, state or local sales, use, value-added or other
taxes, customs duties, or similar tariffs and fees which shall be the
responsibility of Distributor. In the event that Company is required to pay any
such taxes, duties or fees, such items will be added to the invoice to be paid
by Distributor. Company may change the prices of the Products from time to time
with ninety (90) days prior written notice to Distributor.


<PAGE>   3
     such items will be added to the invoice to be paid by Distributor. Company
     may change the prices of the Products from time to time with ninety (90)
     days prior written notice to Distributor.

5.2  All payments shall be made in Dollars currency of the United States of
America. Unless otherwise agreed by Company in writing, terms of payment shall
be by irrevocable letter of credit acceptable to Company.

5.3  In the event Company establishes a line of credit for Distributor or
permits Distributor to purchase products on open account, Distributor grants
Company a continuing security interest in the Collateral in order to secure
payment of its accounts. The term "Collateral" shall mean any Products now or
hereafter acquired by Distributor and all proceeds from the resale of such
Products. Distributor acknowledges that this provision constitutes a security
agreement and authorizes Company to file any financing statement or other
documents necessary to protect Company's security interest in the Collateral.

6.   COMPANY OBLIGATIONS

Company shall, during the term of this Agreement:

6.1  Provide, at no cost, Product training, at mutually acceptable times and
places, for a reasonable number of Distributor's personnel, provided that
Distributor shall pay all expenses of its personnel attending such training
sessions (including without limitation salaries, transportation,
accommodations, meals and related expenses);

6.2  Furnish Distributor, without charge, reasonable quantities of Product
literature and promotional materials, in the English and Spanish languages,
which Company will publish or prepare from time to time; and

6.3  Render reasonable periodic assistance to Distributor on Product technical
and sales issues accordingly to the stated in Section 6.1 above.

7.   DISTRIBUTOR OBLIGATIONS

Distributor shall, during the terms of this Agreement;

7.1  Actively use its best efforts to promote and penetrate the market for the
Products in the Territory;

7.2  Meet the requirements of the Company for warehousing, logistics,
distribution and maintenance of the product. Maintain adequate personnel,
facilities and other resources within the Territory, at its own expense, from
which to sell and distribute the Products;

7.3  Submit to Company regular quarterly status reports on the months of March,
June, September and December, reflecting sales activities and anticipated
requirements of customers in the Territory;

7.4  Furnish Company copies of Distributor's annual financial statements,
credit references from established institutions Distributor has been engaged
with or such other information as Company may reasonably request, if Company
establishes a line of credit for Distributor or permits Distributor to purchase
Products on open accounts in lieu of irrevocable Letters of Credit.

7.5  Not represent, distribute, or otherwise handle competitive products of the
type, size and capability of the Products for a period of the life of the
patents on the Products in Mexico or any other country in the world.



<PAGE>   4

7.6  Maintain adequate insurance in such amounts and with such insurers as is
customary in accordance with sound business practices. At Company's request,
such policies shall name Company as an additional insured and loss payee
thereof, as Company's interests may appear, and shall provide that the insurer
will give Company at least ten (10) days notice of cancellation. At Company's
request, Distributor shall furnish to Company a certificate of insurance or
other evidence satisfactory to Company with respect to the above.

7.7  The Distributor at all times shall carry out its business in such a manner
that it reflects a favorable image of Company and Company's Products, and shall
not act in a misleading business manner, which may result in an error, be
illegal or contrary to commercial ethics and uses.

7.8  The Distributor shall not offer nor sell the Products outside the
Territory as stated in Exhibit B.

7.9  Distributor will provide a "specialty" sales force fully dedicated to
market and sell the Products of the Company within the Territory. The Company
will have direct input into the training and hiring of this sales force, which
will be formed as follows, unless, by mutual agreement, it shall consider as
inconvenient:

<TABLE>
<CAPTION>
YEAR                    1998       1999      2000      2001      2002
<S>                     <C>        <C>       <C>       <C>       <C>
Minimum of fully
dedicated Sales Reps.    4          4         5         5         6
</TABLE>

8.   FORECASTS/ PURCHASE ORDERS/MINIMUM PRODUCT QUANTITIES.

8.1  During the first week of each month, Distributor shall forward to Company
a six (6) month rolling forecast of Product requirements designating the
quantities of the Products which Distributor intends to sell in this period.
Product requirements scheduled for delivery in months 1, 2 and 3 of the rolling
forecast will be considered firm orders and may not be rescheduled or canceled
by Distributor. However, Products scheduled for delivery in months 4, 5 and 6
of the rolling forecast may be rescheduled or canceled by Distributor, subject
to Distributor's Minimum Product Quantities set forth in Section 8.2 below.

8.2  During each Contract Year under this Agreement, Distributor shall purchase
from the Company the minimum quantity of each Product ("Minimum Product
Quantities") that Company and Distributor shall agree upon in advance. The
Minimum Product Quantities for the first 3 (three) Contract Years are shown on
Exhibit C hereto. The Minimum Product Quantities for subsequent Contract Years
shall be submitted by Company to Distributor, after consultation with
Distributor at least ninety (90) days prior to each such Contract Year. If
Company and Distributor fail to agree upon the Minimum Product quantities for
any Contract Year, then the Minimum Product Quantities for such Contract Year
shall be deemed to be ten percent (10%) greater than the Minimum Product
Quantities for the preceding Contract Year. "Contract Year" means for the first
Contract Year the period commencing on the effective date hereof and ending one
year thereafter and for subsequent Contract Years, the successive twelve (12)
month period thereafter. Failure of Distributor to purchase the Minimum Product
Quantities in any Contract Year shall be considered a material breach of this
Agreement.

9.   DELIVERY

9.1  Delivery of all Products ordered by Distributor shall be made C.I.F.
Price. Title and risk of loss to the Products shall pass to Distributor when
Company makes available the Products to Distributor at Distributor's facilities
located in Guadalajara, Jal. Mexico or the named point of shipment. ICC
Incoterms (1990 edition) shall apply, except insofar as these Incoterms may be
inconsistent  with the terms of this Agreement.

<PAGE>   5
9.2  In the event Distributor fails to take delivery and/or shipment of
Products pursuant to the terms of this Agreement: (i) Company shall be entitled
to store the Products in a warehouse at the expense and risk of Distributor;
(ii) the price of the Products shall become immediately due and payable by
Distributor; (iii) if payment is secured by a letter of credit, Company may
receive payment upon presentation of its sales invoice and warehouse receipt;
and (iv) after sixty (60) days from the date upon which the price becomes
payable, Company may dispose of the Products in a commercially reasonable
manner without notice to Distributor and recover any shortfall and related
expenses from Distributors.

9.3  All Products ordered pursuant to accepted purchase order shall be
scheduled for delivery in accordance with Company's then current and normal
delivery times.

10.  WARRANTY, QUALITY CONTROL AND INDEMNIFICATION

10.1 Company warrants that the Products, when delivered to Distributor pursuant
to this Agreement, will meet the written Company specifications for such
Products in effect as of the time of such delivery and will be free from
defects in material and workmanship during the warranty period (as defined
below). Subject to Section 1.2, Company reserves the right to amend such
specifications from time to time at its sole discretion. THE FOREGOING WARRANTY
IS EXCLUSIVE AND IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED (INCLUDING
BUT NOT LIMITED TO OTHER WARRANTIES OF MERCHANTABILITY OR FITTENESS FOR A
PARTICULAR PURPOSE). The exclusive remedy for breach of warranty shall be, at
Company's option, the rework or replacement, at Company's expense, of the
non-conforming Product, provided that, such Product is returned to the Company
within six (6) months after delivery (the "Warranty Period"). Distributor shall
notify Company of the nonconforming Product within the warranty period.
Products may only be returned by Distributor when accompanied by a return
material authorization number issued by Company. Shipping expenses for Products
returned by Distributor will be prepaid by Distributor. Company shall pay for
shipment back to Distributor for Products replaced or reworked under warranty.

10.2 Distributor shall not make any representation or warranty as to the
Products except for the warranty stated in Section 10.1 above. Distributor
shall not alter and shall not recommend or knowingly sell the Products for any
uses except as described in Company's Product label and labeling and in
accordance with the written instructions and warnings furnished by Company.
Distributor agrees to deliver to its customers and or before sale all
specifications, inserts, instructions, and warnings furnished by Company and to
retain records evidencing such delivery. Distributor further agrees to notify
Company of any events involving bodily injury or property damages resulting
from the use of any of the Products within three (3) Mexican business days
after Distributor receives notice thereof.

10.3 Distributor shall maintain all records regarding sales and traceability of
Products as required by applicable law or the applicable governmental
authority in the Territory. Periodically, but not less than every three (3)
months, Distributor shall supply Company with a summary report of the
information contained in such records. Upon termination of this Agreement,
Distributor shall deliver such records to Company. Distributor shall not
initiate any recall of any Product without the prior written authorization of
Company; provided that, if a governmental authority requires Distributor to
recall any Product, then Distributor shall immediately notify the Company in
writing of such requirement and the reasons therefor and shall give Company a
reasonable opportunity to consult with the governmental authority prior to
initiating such recall. In the event that Company deems it necessary to recall
any Product or any governmental authority requests recall of any Product
distributed or sold by Distributor in the Territory, Distributor Shall bear all
costs and exposes of such recall, including without limitation expenses or
obligations to third parties, the costs of notifying customers and costs
associated with the shipment of such recalled Products from customers. Company
shall reimburse Distributor for Distributor's reasonable costs of such recall,
provided such recall is a consequence of a product defect caused by Company. In
the event of any recall, Distributor and Company shall cooperate fully with
each other in effecting such recall.
<PAGE>   6
10.4 Distributor agrees to indemnify and hold Company harmless against any
liability, demand, cost or expense (including reasonable attorney's fees)
caused by any claim that is attributable to the failure by Distributor to
perform its obligations hereunder or to Distributor's misconduct or negligence
in the shipment, storage, handling, distribution, promotion or sale of the
Products.

10.5 Except for claims arising under Section 10.4, Company agrees to indemnify
Distributor against any liability, demand, cost or expense (including
reasonable attorney's fees) arising from any third party claim to the extent
such claim is attributable to a product defect caused by Company.

11.  GOVERNMENTAL APPROVALS AND REGISTRATIONS

11.1 With the exception of the health approvals for the Products provided for
in Section 11.2 below, Distributor shall secure (and provide copies thereof the
Company) all necessary governmental permits, licenses and registrations
required in connection with the incorporation and resale of the Products in the
Territory.

11.2 Following clinical trials fully carried out by the Company at the
Company's own cost, distributor shall obtain all necessary health approvals to
lawfully market the Products in the Territory. If such approvals can not be
legally obtained in the name of the Company, then such approvals shall be
obtained in the name of Distributor to be held by Distributor for the sole
benefit of Company. All costs and expenses of obtaining and maintaining such
approvals shall be borne by Company. In connection with obtaining health
approval of any Product, Company shall provide Distributor sufficient
quantities of Product samples (the "Sample Product") as Distributor as
reasonably required by Distributor to comply with legal requirements in
obtaining such health approval. Upon expiration or termination of this
Agreement, the Distributor shall, at the Company's option, transfer to Company
(or its nominee) without compensation all right and title to any or all of the
Product approvals and/or registrations in the Territory.

12.  COMPANY'S PROPRIETARY INFORMATION AND RIGHTS

12.1 Distributor recognizes and understands that all information not generally
known concerning Company and the Products, including but not limited to
Company's organization and business affairs, customer lists, sales information,
operating procedures and practices, technical data, designs, know-how, trade
secrets, and processes (the "Proprietary Information"), whether owned by
Company or licensed by Company from third parties, are subject to a valuable
proprietary interest of Company, and that Distributor is under an obligation to
maintain the confidentiality of such Proprietary Information. Without limiting
the generality of the forgoing obligations, Distributor agrees that for the
term of this Agreement and thereafter until such time as the Proprietary
Information is in the public domain, Distributor will (i) not disclose, publish
or disseminate any Proprietary Information, (ii) not use any Proprietary
Information for its own account, (iii) not authorize any other person to
disclose, publish or disseminate the Proprietary information, and (iv) treat
all Proprietary Information in a confidential manner, including appropriate
marking and secure storage of written Proprietary Information. Company agrees
to maintain the same confidentiality for all of Distributor's Proprietary
Information that might be disclosed to Company and identified by Distributor in
writing when disclosed as its "Proprietary Information".

12.2 Distributor acknowledges that the Company is the owner and/or licenser the
Territory of the trademark(s) appearing on the Product packaging, labeling,
advertisements or promotional material or utilized in the sale of the Products
(the "Trademarks"). During the term of this Agreement, Distributor is
authorized to use the Trademarks solely in connection with Distributor's
advertisement, promotion and distribution of the Products in the Territory.
Whenever the Trademark is used, e.g., on any package, label or advertisement,
the right or most prominent use shall always be accompanied by a legend
acceptable to Company indicating that the Trademark is licensed to the
Distributor by Company.
<PAGE>   7
12.3  Distributor shall neither use nor permit others to use the name "Advanced
Corneal Systems" or any abbreviation or modification thereof, or the Trademarks
or any other trademark or tradename of Company as part of the Distributor's fir
name or corporate titles, in signs or in letterheads without the prior written
consent of Company. Distributor may designate itself as a Director of Products
in the Territory in such form and manner as Company may approve of in advance
in writing. Distributor shall not grant this privilege to any third party or to
any affiliates without Company's prior written consent.

12.4  Distributor acknowledges that Company owns and retains all patents,
trademarks, copyrights and other proprietary rights in the Products, and agrees
that it will not at any time during or after the termination of this Agreement
assert or claim any interest in or take any action which may adversely affect
the validity or enforceability of any trademark, trade name, trade secret,
copyright or other proprietary right owned by or licensed to Company. No
license, either express or implied, is granted to the Distributor by this
Agreement to any patents, trademarks, copyrights, processes, or other
proprietary rights of Company or its affiliates, except the right to sell the
Products sold to the Distributor hereunder in the Territory, and the license to
use the Trademarks in connection therewith.

13.   TERMINATION

13.1  Company or Distributor shall have the right, at its option, to terminate
this Agreement, by given written notice to the other party, effective
immediately upon receipt of such notice, upon the occurrence of any of the
following events:

     (A) In the event that the other party becomes insolvent; proceedings are
instituted by or against it in bankruptcy, insolvency, re-organization or
dissolution; or it makes a general assignment for the benefit of creditors.

     (B) In the event that the other party fails to perform any material
obligation, warranty, duty or responsibility under this Agreement (including
without limitation Distributor's obligation to pay Company amounts owning
Company when due and Distributor's obligations under Section 8.2) and such
failure continues unremedied for a period of thirty (30) days following written
notice thereof.

13.2  Upon termination hereby by either party:

13.2.1  All sums due to either party from the other shall be promptly paid;

13.2.2  Distributor orders received and accepted by Company prior to the
effective date of the termination of this Agreement shall be fulfilled in
accordance with their terms;

13.2.3  All property belonging to one party but in the custody of the other
shall be returned;

13.2.4  Company shall have the option to repurchase any or all current and
resalable Products in Distributor's inventory at Distributor's inventory at
Distributor's original net purchase price;

13.2.5  Distributor shall cease all display, advertising and use of Company
tradenames, trademarks (including the Trademarks), logos and designations,
except uses on the Products which remain in Distributor's possession in
accordance with this Agreement;

13.2.6  Distributor shall, at the Company's option, transfer to the Company (or
its nominee), without compensation, all right and title to any or all of the
product approvals and/or registrations in the Territory, and shall execute at
Company's request all the documents required under the territory laws to
complete such transfer.

13.2.7  Neither party shall be liable to the other for loss or damage arising
from termination of this Agreement and Distributor hereby waives any
compensation that would otherwise be payable to it by

<PAGE>   8

reason of such termination.

14.  U.S. LAWS AND REGULATIONS

14.1 Distributor acknowledges that Company has informed it that United States
law and related regulations may under certain circumstances forbid the
re-export of Products (or associated technical data) sold or transferred to
customers in the Territory or elsewhere. Distributor agrees that it will make
every reasonable effort to comply with such regulations, including providing
customer information required by Company to comply with United States and local
country laws and regulations.

14.2 Distributor acknowledges that Company has informed it that United States
law forbids the making of gifts or payments to government employees or
political parties to induce such employee or parties to misuse positions of
influence in order to obtain or retain business. Distributor agrees that it
will not engage in such conduct, nor permit others under its control to make
such gifts or payments.

15.  GOVERNING LAW & ARBITRATION

15.1 This Agreement and any amendment or modification hereof and all rights
hereunder shall in all respect be governed by and construed in accordance with
the laws of Mexico City, D.F.

15.2 For any and all controversies arising from or with respect to this
Agreement and the interpretation hereof the parties shall submit to the
International Rules of Arbitration of the Mexican Chapter of the International
Chamber of Commerce (C.I.C.), as amended from time to time, for all matters not
otherwise covered in the following paragraph:

15.2.1 The arbitration shall be conducted in the Mexico City, unless Company
and Distributor mutually agree to another location.

15.2.2 The arbitration demand notice and any notices resulting from the
arbitration shall be made to the domiciles set forth by the parties herein
below by certified mail with return receipt of specialized messenger service
(e.g. DHL, Federal Express), or by any other valid means of notice in
accordance with the applicable legislation of the domicile of the party
receiving notice. The arbitration shall commence on the date when the
arbitration demand notice is delivered to the party receiving the demand
notice. A copy of such notice shall be delivered simultaneously to the C.I.C.

15.2.3 In order to calculate the terms in accordance with the present clause,
the working day following the date on which a notice is delivered shall be
used. If the last day of such term is not a working day in the place of
delivery, the term shall be extended to the following working day. If there are
various non-working days in any term, such days shall be included to compute
such term. All terms relating to the arbitration shall be computed as calendar
days.

15.2.4 The arbitration demand notice shall include the following information as
well as other information required by the C.I.C.:

a.) the demand for which the dispute is submitted to arbitration;

b.) the names and address of the party;

c.) a reference to the present clause or to the guaranty trust agreement
contained in this instrument;

<PAGE>   9

d.) a reference to the contract or document from which the dispute arises; and

e.) a description of the Event of Default and the obligations and damages
    claimed.

15.2.5 The party to whom demand notice is served shall have a term of fourteen
(14) days from the date of delivery of the arbitration demand. In the event
that such receiving party does not answer the demand within such term, he shall
be held in default and such default shall constitute an admission by the
receiving party of the allegations set forth in the arbitration demand.

15.2.6 The arbitrator shall be designated by the C.I.C. within seven (7) days
(or such longer period as required by the AAA) following the delivery of the
arbitration demand notice and such arbitrator shall have the required
experience relating to the nature of the Event of Default. The designation of
the arbitrator shall not be object to be either of the parties.

15.2.7 Within three (3) days following the termination for the answer of the
demand, the arbitrator shall notify the Company and the Distributor with at
least thirty (30) days notice prior to the date on which the arbitration
hearing shall be carried out, indicating the place and the time when such
hearing will take place. The hearing shall be carried out in a term no greater
than three (3) days, unless the arbitrator determines that a greater term is
necessary.

15.2.8 At least fifteen (15) days prior to the date of the hearing, the Company
and the Distributor shall deliver to the arbitrator: (1) the names and
addresses of any witnesses that they intend to present and a sworn declaration
(affidavit) duly signed by each witness that shall detail the content of his or
her testimony at the hearing; (ii) the documents that will be presented at the
hearing; and (iii) a brief which details the evidence that will be presented at
the arbitration.

15.2.9 The applicable legislation shall be that which corresponds to Mexico
City. The arbitration shall be conducted in the Spanish language.

15.2.10 The party that prevails in the arbitration shall have the right to
receive payment for its lawyer's fees and costs and expenses incurred in
connection with the arbitration, including, but not limited to, expert fees.

15.2.11 The arbitral award shall be final and non-appealable and shall obligate
Company and Distributor. In the event necessary, the arbitral award shall be
executed by any competent court.

15.2.12 For the purposes of paragraph 15.2 hereof, the parties shall have the
following domiciles:

COMPANY:                              DISTRIBUTOR:

ADVANCED CORNEAL SYSTEMS, INC.        LABORATORIOS SOPHIA, S.A. DE C.V.
15279 ALTON PARKWAY, SUITE 100        AV. HIDALGO #738
IRVINE, CALIFORNIA 92618              GUADALAJARA, JAL.
USA                                       MEXICO

ATTN: MR. EDWARD H. DANSE             ATTN: MR. FERNANDO SANCHEZ BECERRA

ccp.  Ortega y Videgaray              ccp.  Cuesta Campos Y Associados, S.C.
      Yautepec #12                          Lic. Fernando Cuesta L.
      Col. Condesa                          Bismark #192 P.B.
      Mexico, D.F. 06140                    Guadalajara, Jal., CP. 44690
                                            Tel: 6-30-05-80  6-30-21-29














<PAGE>   10
16.  LIMITATION OF LIABILITY

16.1 Neither Company nor Distributor shall be liable to the other, or to
Distributor's customers, for any special, indirect, or consequential damages,
including but not limited to loss of profits, loss of business opportunities,
or loss of business investment.

17.  SURVIVAL

17.1 In addition to Distributor's obligation to pay Company all amounts due
hereunder, the provisions under Sections 10, 11, 12, 13, 15 and 16 shall
survive termination of the Agreement, as well as such other provisions which by
their meaning and intent have applicability beyond the terms of this Agreement.

18.  ASSIGNMENT

18.1 This Distribution Agreement shall be binding upon and shall innure to the
benefit of the parties and its successors and assigns. The Distributor shall
not be able to assign its rights and/or obligations hereunder or sell or
transfer a majority of its ownership interests without the prior written
consent of Company. Company may at any time without obtaining the consent of
Distributor may sell, assign, negotiate or otherwise transfer to any third
party all or any part of, or any interest in, the rights and benefits contained
hereunder and, to the extent of such assignment, such assignee shall have the
same rights and benefits against the Distributor as it would have had if it was
Company.

19.  INTEGRATED AGREEMENT

19.1 This Agreement constitutes the entire understanding and agreement between
Company and Distributor and terminates and supersedes all prior formal or
informal understandings.

20.  FORCE MAJEURE

20.1 Performance of the parties hereto of their respective obligations
hereunder shall be subject to force majeure and acts of God, including but not
limited to, insurrections, riots, wars and war-like operations, explosives,
governmental acts, epidemics, failure of contractors to perform, strikes,
fires, accidents, acts of any public enemy, inability to obtain required
materials, supplies, products or qualified labor, delay in transportation and
any applicable law, regulation, or restriction of any foreign, federal, state
or local governmental entity or instrumentality. However, the parties hereto
shall use their best efforts to avoid, remove or cure said circumstances. Any
party temporarily excused for performances hereunder by any such circumstance
shall resume performance with utmost dispatch when such circumstances are
removed or cured. Any party claiming such circumstances as an excuse for delay
in performance shall give prompt notice in writing thereof to the other party.
Nothing herein and no contrary provisions of any law, regulation, or
governmental pronouncement shall, however, relieve the Distributor of its
obligations to make the payments to Company required hereunder at the times and
in the manner specified.

21.  NO WAIVER

21.1 No waiver by either party of any breach or default of any of the covenants
or agreements herein contained shall be deemed a waiver as to any subsequent or
similar breach or default. No right or remedy herein conferred upon either party
is exclusive or any other right or remedy herein or by law provided or
permitted.


<PAGE>   11
22.  SEVERABILITY

22.1 This Agreement is divisible, and provisions herein held to be violative of
any applicable treaties, statutes or regulations of any governmental agency
having jurisdiction shall effect only that portion held to be invalid or
inoperative, and the remaining portions of this Agreement shall remain in full
force and effect.

23.  COUNTERPARTS

23.1 This Agreement may be executed in duplicate counterparts, each of which
shall be deemed to be an original; provided however, such counterparts shall
together constitute only one instrument.

24.  NOTICE

24.1 Notices to be given to any party under this Agreement shall not be
effective unless in writing and hand-delivered or mailed by certified or
registered mail to the party to whom notice is to be given at the address dated
on the cover page thereof or sent by telefax to the party to be notified to
such telefax number as such party hereafter designates by written notice to the
other party. Notices sent by mail shall be deemed to have been given ten (10)
days after the postmark thereof. All other notices shall be deemed to have
given on the date of receipt thereof. Any party may change its address by
giving written notice of such change in the manner provided herein.

25.  LANGUAGE

25.1 This Agreement has been written in the English language. It may be
translated, for convenience, into other languages. However, in the case of
conflict or disagreement, the executed English language version shall prevail.

IN WITNESS WHEREOF, Company and Distributor have duly executed this Agreement.


/s/ [SIGNATURE ILLEGIBLE]              /s/ EDWARD H. DANSE
---------------------------------      -----------------------------------
Laboratories Sophia, S.A. DE C.V.      Advanced Corneal Systems, Inc.

Director General                        President & CEO
---------------------------------      ------------------------------------
Title                                  Title

23 April 1998                          April 23, 1998
---------------------------------      ------------------------------------
Date                                   Date
<PAGE>   12
                                   EXHIBIT A

PRODUCTS:

Initially, this Agreement includes only one product named VITRASE(R) (one vial
for one treatment)

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX


       /s/ [Signature Illegible]               /s/ EDWARD H. DANSE
<PAGE>   13
                                   EXHIBIT B

TERRITORY:

This Agreement initially includes the country of Mexico.

PRICE:

Distributor shall pay to the Company 75% from final actual retail price
(selling price to the public). Expected retail price in Mexico and the United
States of America is $500.00 USD per vial.

Any change on retail price for this product in Mexico shall be made by mutual
agreement between Company and Distributor and, one copy from Price Increase
Authorization released by SECOFI (if proceeds) shall be delivered to the
Company's files.

Company reserves the right to review all Distributor's invoices for this
product in a quarterly basis.

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX


       /s/ [Signature Illegible]               /s/ EDWARD H. DANSE
<PAGE>   14
                                   EXHIBIT C

                           MINIMUM PRODUCT QUANTITIES


YEAR                MINIMUM PRODUCT QUANTITIES

1998                800 units.

1999                Established by mutual agreement.
                    To be determined by or before March 31st, 1999

2000                Established by mutual agreement.
                    To be determined by or before September 30th, 1999

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX


       /s/ [Signature Illegible]               /s/ Edward H. Danse