Alcon's (ALC) move to acquire STAAR Surgical (STAA) in a $1.5 billion transaction is being opposed by Broadwood Partners, which holds approximately 27.5% stake in STAAR Surgical, according to a Wednesday filing.

Broadwood Partners has filed a definitive proxy statement and GREEN proxy card with the US Securities and Exchange Commission and sent a letter to its fellow stockholders in connection with its opposition to the proposed acquisition.

In its letter to shareholders, Broadwood said STAAR turnaround prospects look good and that the price of $28 a share does not reflect the value and future promise of the business.

It also said the board of STAAR chose not to engage with other companies that may have been interested in the transaction and sought only to engage with Alcon.

However, STAAR Surgical in a statement on Monday said at the expiration of the 45-day "window shop" period no competing acquisition proposal was received, despite Broadwood Partners' active exploration of alternative buyers over the past 45 days.

STAAR Surgical shares were down 1.1% in recent premarket activity.