Diffuse Unilateral Subacute Neuroretinitis (DUSN)


History of Present Illness

A 56-year-old man presents with a paracentral blind spot and floaters right eye (OD), but no ocular pain, for about 4 weeks. He first noticed the blind spot while hunting in Michigan and closing his left eye (OS). He has been in excellent health and enjoys hunting, fishing, and swimming in the outdoors. He does not recall being bitten by an insect or tick this fall while hunting deer.

Exam
OD OS
Visual acuity 20/60 20/20
Intraocular pressure (IOP) (mm Hg) 10 9
Sclera/conjunctiva Clear. No injection Clear. No injection
Cornea Clear Clear
Anterior chamber (AC) No cell or flare No cell or flare
Iris No relative afferent pupillary defect (RAPD) Normal
Lens Clear Clear
Vitreous cavity 2+ vitritis Clear
Retina/optic nerve White worm within the macula ( Fig. 44.1 ) Normal

Fig. 44.1, ( Left panel ) Live white subretinal nematode within the vascular arcades (OD), which migrated over time ( right panel ).

Questions to Ask

  • Have you been in the woods within the past 3 months hunting or swimming in rivers?

  • Do you eat the animals that you have hunted?

  • Have you eaten steak tartare or other raw meat in the past?

  • Do you have unprotected sex with women or men?

  • Have you traveled to the tropics within the past 6 months?

He has been hunting in Michigan for the past 3 months during the fall deer season and was successful in bringing down a white-tailed deer as part of a deer culling program in Ann Arbor. He does not usually eat game, but he and a few friends had a cookout at the end of the day. He has not had unprotected sex with either gender and has never been to the tropics.

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