Bausch & Lomb Inc. on Tuesday requested that rival Advanced Medical Optics Inc. revise its unsolicited $4.23 billion bid to buy the eye care company, which plans to instead accept Warburg Pincus' $3.67 billion offer.

In its letter to AMO on Tuesday, Bausch & Lomb asked for the revisions by Friday, and said that without them, AMO's offer would not likely result in a superior proposal.

Bausch & Lomb said it had concerns that AMO would have trouble getting shareholder approval for its proposed $4.23 billion acquisition.

AMO's third-largest shareholder, ValueAct Capital, earlier this month said it opposed the company's takeover bid.

AMO has offered $75 per share in cash and stock and must win the blessing of antitrust officials. Warburg's $65 per share cash bid already has antitrust approval.

Bausch & Lomb must weigh the higher price and potential risks associated with the AMO offer against the lower value, but greater security of the all-cash bid from Warburg Pincus. Warburg Pincus is not expected to raise its offer to thwart the AMO offer, sources said.

(Additional reporting by Jessica Hall)