An in-depth investigation is opened when the Commission has concerns that a transaction could restrict competition in the internal market and the parties have not offered satisfactory commitments to resolve those concerns.
The Commission will investigate the effect of the merger on the market for ophthalmic lenses and eyewear, it said.
The companies are leaders in the optical industry, the Commission said. Essilor is the largest supplier of ophthalmic lenses, both worldwide and in Europe, while Luxottica is the largest supplier of eyewear worldwide and in Europe. Both companies sell their products to opticians who then sell finished spectacles and sunglasses to consumers.
The Commission is concerned that the merged entity could use Luxottica's brands to convince opticians to buy Essilor lenses and exclude other lens suppliers from the markets, through practices such as bundling or tying, it said. This could limit purchase choices or increase prices.
The investigation will also look at whether the merged company would use Essilor's strength in ophthalmic lenses to exclude rival eyewear suppliers from the markets, and whether the merger would remove emerging competition from Luxottica in lenses and from Essilor in eyewear.
Commissioner Margrethe Vestager, in charge of competition policy, said: "Half of Europeans wear glasses and almost all of us will need vision correction one day. Therefore we need to carefully assess whether the proposed merger would lead to higher prices or reduced choices for opticians and ultimately consumers".