In the 1830s and 1840s, a particular disease named ‘military ophthalmia’, a contagious inflammation of the eyes that reigned most forcefully among soldiers, turned into an epidemic in Belgium, spreading between the army and the general population. This article scrutinizes the efforts of the Belgian military health service to contain the epidemic. It places the actions of the Belgian army doctors within a broader development : the emergence of ophthalmology as a specialized medical subfield, in which also ‘civil’ physicians participated. For no more than the epidemic itself respected the boundaries between army and society, did medical knowledge on the disease remain limited to the military. By including both this scientific debate on ophthalmia and the public debate on the disease in the Belgian parliament and general press into the analysis, an image of the Belgian army doctors appears as an ‘open’ community, of which the members easily crossed the borders between the army and civil society. The article therefore contributes to our understanding of the army as an actor in broader histories of medicine, public health and disability.