The human eye, as an organ, can offer critical clues to the presence of systemic disease. This article discusses the various ophthalmologic manifestations of systemic disease that can be evident on examination by an emergency department provider, as well as some findings that can be discerned with specialty consultation. The following topics are reviewed with respect to potential ocular signs and complications: syphilis, herpes zoster, Lyme disease, acquired immunodeficiency syndrome, Reiter’s syndrome, Kawasaki’s disease, temporal arteritis, endocarditis, hypertension, and diabetes mellitus. Indications for emergent ophthalmologic consultation are also emphasized.