Zurich: Under Swiss law, Novartis can force through the deal once it takes majority control from Nestle as mergers require approval of two thirds of shareholders and a simple board majority.

"Novartis has taken the gloves off and claims that since this is not a tender offer, minority owners have no option but to approve the deal, since Novartis will soon control Alcon's board," Kepler Capital Markets analyst Tero Weckroth said.

While Alcon, founded in 1945 by two pharmacists in Texas, is listed on the New York Stock Exchange, it is incorporated in Switzerland and is thus bound by law there.