Relative to other specialties, ophthalmologists deal infrequently with uncertainty. Of course, every patient requires advice, which in turns requires a weighing of risks and benefits, and some pondering of potential unknowns. But unlike internists, ophthalmologists often see the pathology directly. And what once was hidden from us is now rapidly being revealed with new technologies like optical coherence tomography and adaptive optics. Within the ophthalmic kingdom, however, some subspecialties deal with more uncertainty than others. Specialists in uveitis, in particular, often confront uncertainty. Is the pathology autoimmune or infectious? Or even possibly a malignancy like lymphoma? And nothing confounds a uveitis specialist more than tuberculosis in the eye. The obsessive, existential contemplation of Hamlet, “To be or not to be,” parallels the conundrum for many uveitis specialists: TB or not TB?

To diagnose many specific subsets of uveitis such as that associated with ankylosing spondylitis, sarcoidosis or syphilis, skilled clinicians rely on diagnostic tests. But the interpretation of those tests requires a context. The physician needs to know the sensitivity and specificity of the test as well as what is known as the pretest probability. In this issue of the BJO, Hong and colleagues from the University of Southern California (USC) in Los Angeles report on a review of 141 patients with uveitis.1 They find that six of these patients or 4.3% of the clinic population had a definite or presumptive diagnosis of ocular tuberculosis. The prevalence of tuberculosis is low in North America compared to Europe; and it is low in Europe compared to many parts of the world such as India or Saudi Arabia. The prevalence noted in …