Role of imaging in the diagnosis of optic nerve avulsion

Case Summary A case of a 26-year-old male presented with a sudden, complete loss of vision in the right eye (OD) following a road traffic accident, associated with periocular bleeding. He had undergone a right upper eyelid laceration repair and removal of a superficial wooden foreign body elsewhere. On examination of the OD, there was no light perception, mid-dilated fixed pupil, restriction of extraocular movements, and conjunctival chemosis with multiple iris tears. Palpation revealed a firm, mobile mass over the upper eyelid suggestive of a retained foreign body. Dilated fundus examination revealed optic nerve head avulsion with vitreous hemorrhage [Figure 1]. No abnormality detected on examination of the left eye (OS).Figure 1: Colored Fundus photograph of OD showing optic nerve head avulsion (green arrow) with surrounding peripapillary hemorrhage, along with vitreous hemorrhageB-scan ultrasonography showed an altered contour at the optic nerve–globe junction with a hypoechoic area suggestive of optic nerve head avulsion [Figure 2]. Contrast-enhanced magnetic resonance imaging (MRI, T2-weighted) demonstrated discontinuity at the optic nerve insertion [Figure 3], whereas T1-weighted imaging revealed a 2.8 mm linear wooden foreign body along the medial orbital wall indenting the globe [Figure 4]. The patient was managed with initial medical therapy followed by wound exploration and successful removal of the retained foreign body, with nil visual prognosis explained.Figure 2: B-scan ultrasonography of OD demonstrating altered globe–optic nerve junction contour (red arrow) with adjacent hypoechoic area suggestive of optic nerve head avulsionFigure 3: T2-weighted contrast-enhanced magnetic resonance imaging showing discontinuity at OD optic nerve insertion site (yellow arrow)Figure 4: T1-weighted contrast-enhanced magnetic resonance imaging demonstrating a linear wooden foreign body (red arrow) along the medial orbital wall indenting the globeDiscussion Optic nerve head avulsion is an uncommon ocular injury involving traumatic separation of the optic nerve fibers from the globe at the lamina cribrosa due to sudden globe rotation, anterior displacement, or acute intraocular pressure rise, leading to disinsertion of the optic nerve at the lamina cribrosa.[1,2] It is most often associated with high-impact blunt trauma, including road traffic accidents and sports injuries.[3] The condition may be clinically missed in the acute phase due to overlying media opacities like vitreous hemorrhage, and imaging modalities such as B-scan ultrasonography, computed tomography (CT), or MRI are often required for confirmation.[2] B-scan ultrasonography may reveal contour irregularity or hypolucency at the nerve head, but MRI offers superior soft-tissue resolution, aiding detection when CT is inconclusive. Retained organic foreign bodies pose additional diagnostic and infectious risk; MRI (in nonmetallic cases) or CT (in metallic cases) is essential for localization. Prognosis is generally poor, with most cases ending in no light perception vision despite intervention.[1] Despite prompt recognition and intervention, visual prognosis remains extremely poor in patients with complete avulsion. This case highlights the role of imaging in confirmation of optic nerve avulsion, which is a clinical diagnosis if the posterior segment is visible at the time of examination. One should be aware that imaging plays an important role in cases where there is no view of the posterior segment or confirmation of optic nerve avulsion. Even if the media is clear from a medico-legal standpoint, one should be mindful that imaging is crucial in these situations. Furthermore, one should enquire about the mechanism of trauma, which may be important for high suspicion and prompt localization and removal of the retained foreign body. However, vision may not be salvaged in most of the optic nerve avulsion cases. Data availability statement The data supporting the findings of this study will be made available upon reasonable request. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given their consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.