As a student, he was affiliated with the military teaching hospital of Utrecht led by Professor Antoine Gérard van Onsenoort.
[4] In 1837, during a medical trip to the south of France, he collected clinincal observations and shared the opinions and doctrines of the University Hospital of Montpellier.
[8] As a corresponding member of the Society of Sciences, Arts and Letters of Hainaut, he presented his work on blepharitis titled Considerations on catarrhal blepharophthalmia of the armies (French: Mémoire sur la blépharophtalmie catarrhale des armées Belges) on April 16, 1838.
[11] Throughout 1839, he continued his service as a military physician in Namur, offering free consultations to ophthalmologists at his home and traveling to see patients.
[4] With over 18,000 patients seeking his expertise and undergoing surgery at his dispensary, Cunier also drew Belgian students and foreign doctors to his clinical lessons on ophthalmology.
By 1845, the surgeon of the Ophthamologic Institute was a corresponding member of many of the academies of medicine and medical societies internationally including Amsterdam, Angers, Antwerp, Baden, Barcelona, Berlin, Bordeaux, Bruges, Brussels, Copenhagen, Coruna, Dresden, Erlangen, Ghent, Halle, Hamburg, Heidelberg, Hoorn, Liege, Lisbon, London, Lyon, Madrid, Malines, Mons, Montpellier, Nantes, New Orleans, Palma de Mallorca, Paris, Port of Santa María, Rio de Janeiro, Rotterdam, Sarragosse, Strasbourg, Valence, Verviers, and Vienna.
Soon after, the Provincial Ophthalmic Institute of Brabant was established and opened on 10 September 1849, on Boulevard du Jardin botanique, with Dr. Cunier as chief surgeon and Dr. Joseph Bosch as assistant physician.