In 2018, market conditions in eye wear continued to be favorable overall, being the GrandVision's strongest year of top-line growth since 2015, as we achieved 10.3% revenue growth at constant exchange rates, with 3.4%
comparable growth. We have also made a good step towards our goal of increasing the share of our e-commerce sales which were up more than 60% in 2018 with pure online sales in the contact lens category now approaching 10% of total category sales.
Demand for eye care continues to be driven by long term demographic trends as well as consumers' focus on value and quality. These favorable underlying market trends and the continued execution of our commercial strategy.
As a result, we further increased our global market share and strengthened our position as a leading global optical retailer.
We are pleased with the performance across the Group as we continue to make progress towards our primary strategic initiative of driving sustainable, profitable growth across the business over the longer term.
Number of stores
Number of own stores
Number of franchise stores
Number of countries in which GrandVision is present
Number of retail banners
Number of employees (average FTE)
At the end of 2017, GrandVision completed two sizable acquisitions of optical retail chains in Europe, the majority stake in Visilab, a leading optical retail chain in Switzerland and the acquisition of Tesco Opticians in the United Kingdom.
Overall, acquisitions added 6.4% to revenue growth during 2018.
In 2018, GrandVision expanded its store network by 94 stores, mainly through the continued organic expansion of its store base, leading to a total of 7,095 stores at year-end 2018, of which 5,897, or 83%, were own stores and 1,198 were franchise stores.
Number of total stores
The G4 and the Other Europe segments contributed the most to global store network growth during the year with total net store openings of 75.
In the Americas and Asia segment, the number of stores was impacted by the termination of an agreement with a department store chain in Chile as well as selective store closings in Brazil, Colombia and Peru to enhance profitability in these markets, offsetting continued openings in Mexico, Turkey and the United States.