BRUSSELS, July 17 (Reuters) - EU antitrust authorities have extended their investigation into Ray-Ban maker EssilorLuxottica's 7.2 billion euro ($8.2 billion) bid for Dutch opticians group GrandVision by a week to Aug. 27.

This is the third extension since the Commission launched a full-scale investigation on concerns that the deal could harm competition, suggesting clearance of the takeover is conditional on concessions from EssilorLuxottica.

"The (European) Commission extended the deadline in agreement with the parties," the EU competition enforcer said in a statement.

EssilorLuxottica, which owns the Oakley and Persol brands and Varilux lenses, was formed last year from the merger of French lens maker Essilor and Italian eyewear group Luxottica. ($1 = 0.8751 euros) (Reporting by Foo Yun Chee Editing by David Goodman )