A 30-year-old woman with vision loss and painful eye movements.

A 30-year-old woman presented to the emergency department with a two-day history of pain in her right eye that was worse with eye movements. She also complained of blurred vision in the right eye. She had no float-ers or eye redness and did not have recent trauma. Her ocular and medical history were unremark-able, and she was not taking medications. On physical examination, the patient appeared well and had normal vital signs. Her best corrected visual acuity was 20/50 in the right eye and 20/20 in the left eye, and the intraocular pressures were normal at 13 mm Hg. The patient had a relative afferent pupillary defect in her right eye, and her extraocular movements were full. There was no proptosis or periorbital swelling. Findings on slit-lamp examination were normal, and fundu-scopic examination with pupil dilation showed a normal macula, peripheral retina and optic nerve. Results of a full neurologic examination were otherwise normal. What is the most appropriate next step? a. Order complete blood count, antinuclear anti-body test and venereal disease research laboratory test b. Diagnose optic neuritis and arrange for non-urgent magnetic resonance imaging (MRI) of the brain with ophthalmology follow-up c. Obtain computed tomography of the orbits to rule out compressive lesion of the optic nerve d. Perform lumbar puncture to rule out infectious causes and for oligoclonal band screening of the cerebrospinal fluid (CSF) The answer is (b). Optic neuritis is an inflamma-tory, demyelinating disease of the optic nerve typically diagnosed on clinical grounds without neuroimaging. (By convention, the term " optic neuropathy " will be used in this article when the cause of inflammation of the optic nerve is not demyelination.) Laboratory and imaging studies may be used for prognostic purposes, but they are not required. As was the case with this patient, the typical person with optic neuritis is young (mean age 32 yr), female (3:1 ratio of women to men) and white (> 75% of patients). 1 Patients present with subacute loss of vision that develops over hours or days. In most instances, the vision loss is associated with orbital pain (in 92%) that is worse with eye movements (in 87%). 1 The pain is thought to be due to mechanical irritation of the inflamed optic nerve. 2 About one-third of patients also note photopsia. 1 An important finding on physical examination is a relative afferent pupillary defect, which is always seen in …