Sudden Unilateral Vision Loss in a Teenage Girl

Presentation

An 18-year-old girl presents to the emergency department with acute loss of left-sided vision upon awaking. She states she cannot see “anything” out her left eye, including light or shadows. She reports having normal vision before going to bed. She denies any preceding symptoms of floaters, blurry vision, eye pain, headaches, weakness, numbness, or trauma. She has not previously had any vision problems and does not wear contact lenses or use glasses. There is no history of recent illness; she does have seasonal allergies. She has a medical history of type 1 diabetes mellitus, but she maintains good glycemic control and is compliant with her insulin regimen. Her physical examination reveals a well-appearing patient who is in no acute distress. She is afebrile without tachycardia or tachypnea; her blood pressure is 110/75 mm Hg. Visual acuity testing shows 20/20 in her right eye with normal visual field testing; the left eye is unable to be tested as she states she cannot see and appears to lack light perception. Her extraocular muscles are grossly intact bilaterally. There are no signs of trauma. She has a brisk left afferent pupillary defect. Fluorescein drops are instilled and there is no uptake. Slit lamp examination shows normal conjunctiva, anterior chamber, cornea, iris, and lens. She is examined with dilating drops; the vitreous is clear, the optic disc is sharp and clear, and the ocular vessels appear normal. There are no lesions involving the periorbital skin. Her tympanic membrane is normal, as is the canal. Her oropharynx examination is unrevealing. The remainder of her neurologic examination is normal. An imaging test is obtained, revealing …