Optic Nerve Lost in a Blink – Traumatic Complete Optic Nerve Avulsion

A 4-year-old girl presented to us with sudden vision loss in her right eye following stick injury. Her vision was no light perception, and further examination revealed a lower lid and conjunctival tear, paracentral epithelial defect, and streak hyphema. Fundus examination elicited a complete optic nerve avulsion (ONA) [Figure 1a] with inferior pre-retinal haemorrhage, which was confirmed on B-scan [Figure 1b]. The lid tear was repaired, and other afflictions were managed conservatively. No visual improvement was noted during the follow-up period of 1 year.Figure 1: (a) – Fundus photograph depicting ONA taken on day 30 from trauma. A complete circumferential optic nerve head excavation is seen along with curling of vessels. (b) – B-scan image taken on day 1 from trauma. A hypoechogenic defect (arrow head) is seen in the region of the optic nerveDISCUSSION ONA is a rare form of traumatic optic neuropathy occurring following trauma, which shreds the optic nerve fibres without damaging the nerve sheath occurring due to the disinsertion of the nerve fibres from the globe at the lamina cribrosa, resulting in permanent visual loss.[1] The proposed pathogenetic mechanism is the rabid rotation of the globe and its forward propulsion or a sudden increase in intra-ocular pressure whipping off the optic nerve from the sclera into the nerve sheath.[2,3] This similar mechanism was reported for ONA following a finger poke injury to the eye.[2] Diagnosis can be readily made clinically on fundus examination. However, associated posterior segment haemorrhage might obscure the disc and, thus, interfere with the diagnosis. In such scenarios, imaging modalities such as computed tomography, magnetic resonance imaging, and B-scan come to rescue. The first two investigations are usually limited by their availability and financial constraints, which makes B-scan a readily available, affordable alternative. On B-scan, ONA is usually seen as a hypoechogenic defect in the posterior wall of the globe in the region of the optic nerve [Figure 1b].[4] The visual prognosis of ONA is dismal without any known medical or surgical treatment.[1-4] Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.