In 1980, Sagnières moved to Tahiti in French Polynesia and joined Plastiserd LLC, eventually becoming the managing director.

[5] On 24 November 2011, Essilor's board of directors appointed Sagnières as chairman and CEO of the Group from 2 January 2012, succeeding Xavier Fontanet.

[15] In February 2015, he announced the launch of the "Vision For Life" programme at Essilor, administered by two non-profit organizations and committed to fund 30 million euros to associations in relation to visual health.

The Eye Mitra programme consists in training young primary vision care providers to bring visual healthcare to those living in remote areas of India.

[citation needed] In April 2018, Sagnières announced Essilor's partnership with the Vision Catalyst Fund to provide ophthalmic lenses to 200 million people in the Commonwealth living below the poverty line.

[21] In December 2018, Sagnières was present at the signature of the Letter of Intent between Essilor with the Royal Government of Bhutan and the Central Monastic Body to strengthen the country's vision care infrastructure.

Essilor has pledged to provide 400,000 pairs of eyeglasses for free which will be distributed to all Bhutanese citizens in need and help in strengthening the capacity of health professionals on vision care through the help of training programs and tools.

[22] During a panel discussion on the sidelines of the 74th Session of the United Nations General Assembly on 24 September 2019, Sagnières presented Essilor's evidence-based report, which includes analytical support from McKinsey & Company and quantifies the scale of the "uncorrected poor vision crisis" as well as relevant solutions.

"[27] In 2023 Sagnières published a non-fiction book, Daring French Explorations 1714-1854, Trailblazing adventures around the world, Flammarion.