Correct! You are looking at a swollen left optic disc. At this patient’s young age, the mechanism is probably inflammation, and the condition is labeled “papillitis.” It is a form of primarily intraocular (rather than retrobulbar) optic neuritis. Because trigeminal afferents do not penetrate that part of the optic nerve, there is no periocular pain. Brain/orbit MRI may show enhancement of the optic disc and sometimes intraorbital parenchymal or dural enhancement of the optic nerve. Perifoveal yellow exudates (“macular star figures”)

often become more apparent within 2 weeks after clinical onset, reflecting the intense leakage of papillary capillaries, and generating the label “neuroretinitis,” although this condition is not really a retinal inflammation. Multiple sclerosis does not develop. An evaluation for systemic infectious (including syphilitic) and non-infectious inflammatory disorders is reasonable, but often no cause is found. Cat scratch disease may be diagnosed if a positive Bartonella serum antibody turns up. Most patients who have no signs of infection are treated with corticosteroids, although no controlled trials exist to prove benefit. Substantial visual recovery occurs without treatment in 50% to 75% of cases.