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Show Photo Essay Section Editor: Timothy J. McCulley, MD Optic Nerve Avulsion After Finger-Poke Injury Tapan P. Patel, MD, PhD, Erica L. Archer, MD, Jonathan D. Trobe, MD FIG. 1. A. The right fundus shows vitreous hemorrhage with intraretinal and subretinal hemorrhages surrounding the optic disc, which has a very deep cup. B. Optical coherence tomography of the optic disc demonstrates a bottomless cup indicative of optic nerve avulsion. Abstract: We present a case of optic nerve avulsion as a result of finger-poke injury to the eye. Spectral domain optical coherence tomography demonstrated a plunging cup indicative of the avulsion, a finding not previously described. Optic nerve avulsion is a form of anterior indirect traumatic optic neuropathy evoked by a sudden severe rotation at the junction of the optic nerve and globe Department of Ophthalmology and Visual Sciences (TPP, ELA, JDT), University of Michigan, Ann Arbor, Michigan; and Department of Neurology (JDT), University of Michigan, Ann Arbor, Michigan. The authors report no conflicts of interest. Address correspondence to Jonathan D. Trobe, MD, 1000 Wall Street, Room 8349, Ann Arbor, MI 48105; E-mail: jdtrobe@umich.edu Patel et al: J Neuro-Ophthalmol 2018; 38: 57-59 induced, in this case, by penetration of the finger into the nasal orbit. Journal of Neuro-Ophthalmology 2018;38:57-59 doi: 10.1097/WNO.0000000000000597 © 2017 by North American Neuro-Ophthalmology Society A 17-year-old woman was poked in the right eye by an opponent's finger during a water polo game. She immediately noted reduced vision, tearing, foreign body sensation, and gaze-induced pain in the affected eye. Visual acuity was hand motion in the right eye and 20/ 20 in the left eye. There was a prominent right relative afferent pupillary defect. Intraocular pressures were 15 mm 57 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo Essay FIG. 2. Ultrasound of the right posterior pole (6-posterior transverse view) demonstrates vitreous hemorrhage overlying the optic nerve head, peripapillary retinal edema (arrowheads), and hyporeflectivity posterior to the optic nerve head (arrow), indicating retrodisplacement and edema of the orbital segment of the optic nerve. Hg in the right eye and 17 mm Hg in the left eye. There was no proptosis or ecchymosis of the eyelids or brow. Biomicroscopy of the right eye revealed a 2-cm conjunctival hemorrhagic laceration in the inferomedial fornix. The cornea, lens, and anterior chamber seemed normal. Ophthalmoscopy revealed vitreous, nerve fiber layer, and subretinal hemorrhage (Fig. 1A). The optic disc appeared to have an extremely deep cup, which was confirmed on spectral domain optical coherence tomography (OCT) (Fig. 1B). Orbital CT showed no orbital wall fracture, no orbital or intraocular foreign body, and no radiographic evidence of a ruptured globe. The optic nerve appeared intact without rupture of the optic nerve sheath. At 1 week and 3-month follow-up visits, visual acuity was light perception in the right eye. Vitreous hemorrhage obscured a view of the retina and optic disc. Ultrasound revealed hyporeflectivity behind the optic disc, interpreted as partial avulsion and retrodisplacement of the orbital segment of the optic nerve (1) (Fig. 2). Our case illustrates avulsion of the optic nerve, likely due to a sudden, marked rotation of the eye caused by insertion of a finger into the orbit, an example of anterior indirect rotational traumatic optic neuropathy (TON). Optical coherence tomography demonstrated plunging of the optic disc cup, lending support to the diagnosis, especially where media opacities obscured a view of the optic disc by ophthalmoscopy. Such OCT findings of optic nerve avulsion have not been described previously. Several mechanisms for anterior indirect TON have been proposed, including anterior displacement of the globe, rise in intraocular pressure leading to separation of the optic nerve from the coats of the eye, and sudden rotation of the globe (2,3). In our patient, forceful entry of a finger between the globe and medial orbit likely resulted in rotational forces that 58 rapidly turned the globe and caused high stress at the attachment of the optic nerve to the sclera. This localized stress would be sufficient to result in a complete or partial optic nerve avulsion (4-6). In a finite element model, to simulate the effects of fingertip trauma between the globe and the orbital wall, Cirovic et al (7) found that a relatively minor impact velocity (2-5 m/s) could result in globe rotation of up to 5,000° per second and strain sufficient to cause axonal damage and avulsion of the nerve. As most optic nerve injuries occur in the setting of head injury as a consequence of motor vehicle accidents, falls, or combat-related trauma (8), the mechanisms of TON have parallels with traumatic brain injury (TBI). Diffuse axonal injury, the most common pathologic feature of TBI, is caused by rapid stretching or rotation of white matter tracts (9). Axons in white matter bundles have viscoelastic properties such that they become brittle when exposed to rapid deformations associated with brain trauma (10). Impairment of axoplasmic transport, axonal swelling, and axonal breakage follow (11). Diffuse axonal injury and posterior indirect TON share this common pathophysiology. Based on previous simulations and case reports of optic nerve avulsion after a seemingly "minor" trauma (4,6), the region of the insertion of the optic nerve into the sclera likely represents the anatomic substrate for rotational anterior indirect TON. Traumatic brain injury as a result of penetrating object or bone fracture causing intraparenchymal hemorrhage is similar to direct TON that results in vitreous hemorrhage or optic nerve sheath hematoma. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: T. P. Patel, E. L. Archer, and J. D. Trobe; b. Acquisition of data: T. P. Patel, E. L. Archer, and J. D. Trobe; c. Analysis and interpretation of data: T. P. Patel, E. L. Archer, and J. D. Trobe. Category 2: a. Drafting the manuscript: T. P. Patel, E. L. Archer, and J. D. Trobe; b. Revising it for intellectual content: T. P. Patel, E. L. Archer, and J. D. Trobe. Category 3: a. Final approval of the completed manuscript: T. P. Patel, E. L. Archer, and J. D. Trobe. REFERENCES 1. 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Computer modeling study of the mechanism of Patel et al: J Neuro-Ophthalmol 2018; 38: 57-59 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo Essay optic nerve injury in blunt trauma. Br J Ophthalmol. 2006;90:778-783. 8. Pirouzmand F. Epidemiological trends of traumatic optic nerve injuries in the largest Canadian adult trauma center. J Craniofac Surg. 2012;23:516-520. 9. Meaney FD, Smith DH. Biomechanics of concussion. Clin Sports Med. 2011;30:19-31. Patel et al: J Neuro-Ophthalmol 2018; 38: 57-59 10. Smith DH, Meaney DF, Shull WH. Diffuse axonal injury in head trauma. J Head Trauma Rehabil. 2003;18:307-316. 11. Tang-Schomer MD, Patel AR, Baas PW, Smith DH. Mechanical breaking of microtubules in axons during dynamic stretch injury underlies delayed elasticity, microtubule disassembly, and axon degeneration. FASEB J. 2010;24:1401-1410. 59 Copyright © North American Neuro-Ophthalmology Society. 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