Exhbit 99.1 EXECUTION COPY Alcon, Inc. P.O. Box 62 B sch 69CH-6331 H nenberg Switzerland

We refer you to the Amended and

Restated Registration Rights Agreement, dated as of December 10, 2009 (the

Rights Agreement"), between Alcon, Inc., a company organized under the

laws of Switzerland (the "Company") and Nestl

S.A., a company organized under the laws of Switzerland ("Nestl "), and to the

Registration Rights Agreement, dated as of December 10, 2009 (the "Novartis Registration Rights

Agreement" and, together with the Nestl Registration Rights Agreement,

Registration Rights Agreements"), between the Company and Novartis AG, a

company organized under the laws of Switzerland ("Novartis" and each of

Novartis and Nestl , a "Shareholder"). This

letter agreement sets forth our mutual understanding and agreement regarding the

modification of certain provisions of each Existing Registration Rights

Agreement, as well as the other matters contained herein, in each case to ensure

an orderly and efficient process for any future sales by Nestl or Novartis of

any Registrable Securities and applicable solely in the event that the Purchase

and Option Agreement, dated as of April 6, 2008 (the "Purchase and Option

Agreement"), between Nestl and Novartis is terminated pursuant to

Section 9.5 thereof (the date, if any, of such termination, the "P&O Termination

Date"). Capitalized terms

not defined herein have the meanings ascribed thereto in the Nestl Registration

Rights Agreement or the Novartis Registration Rights Agreement, as

Effective immediately upon the P&O

Termination Date, each Existing Registration Rights Agreement is hereby amended,

without the need for further action by any party, solely to the extent necessary

to give effect to the provisions set forth in paragraphs 1 through 12

the Non-Requesting Shareholder is at the time of the Offer Notice the Priority

Shareholder but does not deliver a valid Priority Notice within the Preemption

Notice Period or waives in writing its right to deliver a Priority Notice, then

the Requesting Shareholder may proceed with the Offering contemplated by the

Offer Notice on the Applicable Offering Period Start Date and the Non-Requesting

Shareholder shall not be permitted to participate in such Offering and shall be

required to comply with paragraph 3 below.

Shareholder shall become the "Priority Shareholder"

and the previous Priority Shareholder shall cease to be the Priority Shareholder

either (i) upon the completion of an Offering by the previous Priority

Shareholder or (ii) if pricing of the relevant Offering triggered by the

delivery of a Offer Notice or Priority Notice by the previous Priority

Shareholder does not occur on or before 11:59 pm New York time, on the last day

of the applicable Offering Period or Preemption Offering Period (the "Outside Time"), as of

the Outside Time. Initially, Novartis shall be the Priority

a Shareholder elects to sell or otherwise transfer, in one transaction or series

of related transactions, 20% or more of its Common Shares to a purchaser or

group of related purchasers in a private transaction not constituting an

Offering that is to be agreed, announced or consummated during such time as the

Stockholder is not the Priority Shareholder, then the Shareholder shall (i)

prior to reaching agreement in principle as to the price and form of

consideration to be paid for such Common Shares with the purchaser, give 60 days

prior written notice to the Priority Shareholder of such proposed transaction

and (ii) from time to time following any such notice, keep the Priority

Shareholder reasonably

regarding the proposed transaction, in the case of each of clause (i) and (ii)

including the name of the proposed purchaser, the number of Common Shares to be

transferred and the proposed price and other material terms and conditions (to

the extent then known).

Avenue of the Americas

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If you are in agreement with the

foregoing, please sign and return to the Company the enclosed copy of this

letter agreement, and upon execution by each of the Company, Nestl and Novartis

it shall become a binding agreement among us.