This patient has optic neuritis associated with her SLE, however due to the consensual response of the pupillary light reflex, shining light in the unaffected eye will produce bilateral miosis.
Miosis (pupillary constriction) is controlled by the pupillary sphincter. Light signals from the outside world, stimulate the optic nerve (cranial nerve II), which projects to the visual cortex via the lateral geniculate nucleus, but also sends nerve fibers to the pre-tectal nucleus. The signals to the pre-tectal nucleus have bilateral projections which stimulate the efferent parasympathetic neurons that innervate the pupillary sphincter. In a patient with optic neuritis, the afferent limb of the pupillary light reflex pathway is damaged, and shining light in the affected eye will not produce miosis. However, due to the bilateral projections of nerves from the Edinger-Westphal nucleus, light shined in the unaffected eye will produce bilateral miosis. This phenomenon is called a consensual response.
Patel and Lundy review the possible ocular manifestations of patients with autoimmune disease. They note that ocular disease may be a sign or a complication of autoimmune disease, and that patients with new visual complaints warrant complete eye exams to rule out trauma and to help proceed towards timely diagnosis.
Suhs et al. conducted a small randomized controlled trial examining the efficacy of erythropoietin in treating autoimmune optic neuritis. They noted that patients treated with erythropoietin had statistically significantly less change in the retinal nerve fiber layer after 16 weeks, as well as trends towards better visual acuity. The authors concluded that erythropoietin may have neuroprotective effects in autoimmune optic neuritis.
Illustration A is a schematic of the pathways involved in the pupillary light reflex.
Video V demonstrates the normal pupillary light reflex and briefly reviews the involved cranial nerves.
Answer 1: Shining light in the unaffected eye would not produce mydriasis in this patient.
Answer 3: There will be miosis of the right eye, however because the efferent arm of the pupillary light reflex is bilateral, the miosis will be bilateral, and not exclusive to the eye.
Answer 4: There will be miosis of the left eye, however because the efferent arm of the pupillary light reflex is bilateral, the miosis will be bilateral, and not exclusive to the left eye.
Answer 5: Although the light source has been moved away from the affected eye, the bilateral parasympathetic innervation of the pupillary light reflex will prevent mydriasis in the affected eye.
Patel SJ, Lundy DC. Ocular manifestations of autoimmune disease. Am Fam Physician. 2002 Sep 15;66(6):991-8. Review. PubMed PMID: 12358224.
PMID:12358224 (Link to Abstract)
Sühs KW, Hein K, Sättler MB, Görlitz A, Ciupka C, Scholz K, Käsmann-Kellner B, Papanagiotou P, Schäffler N, Restemeyer C, Bittersohl D, Hassenstein A, Seitz B, Reith W, Fassbender K, Hilgers R, Heesen C, Bähr M, Diem R. A randomized, double-blind, phase 2 study of erythropoietin in optic neuritis. Ann Neurol. 2012 Aug;72(2):199-210. doi: 10.1002/ana.23573. PubMed PMID: 22926853.
PMID:22926853 (Link to Abstract)
USMLE World Step 1 QBank Question #1735. Copyright © USMLEWorld, LLC 2012