Optic Nerve Avulsion Pattern and Etiologies: A Retrospective Study
Optic nerve avulsion (ONA) is the traumatic separation of the optic nerve fibers at the level of the lamina cribrosa with preservation of the nerve sheath and surrounding sclera. It is a rare but visually devastating form of anterior traumatic optic neuropathy. ONA can be either partial (only the optic nerve is torn) or complete (both the extraocular muscles and the optic nerve are torn, causing total luxation of the ocular bulb). In cases of complete ONA, the optic sheath, which is more elastic than the optic nerve, usually remains attached to the globe, and the optic nerve may appear normal. A complete avulsion causes profound vision impairment, whereas a partial (incomplete) avulsion might result in varying degrees of impairment.
There are several potential causes of ONA including blunt trauma, road traffic accident (RTA), orautoenucleation in psychiatric patients. ONA has been observed from sports injuries in children, falls, and door handle trauma.
The medical records of patients diagnosed with ONA at an Ophthalmic Emergency Department between November 2014 and November 2022 were analyzed in a retrospective cohort study by Mohammad Al Amry et al. Data were collected on patient age, sex, affected eye, cause of injury and imaging studies. The best-corrected visual acuity (BCVA) at presentation and at the last follow-up visit, and the duration of follow-up were documented.
The study sample was comprised of 44 eyes of 43 patients with ONA with median age of 16.5 (9.3–26.8) years ranging from 2 years old to 70 years old. There were (35; 79.5%) males and (9; 20.5%) females. Most cases presented with an affected left eye (27; 61.4%) followed by the right eye (16; 36.4%) and only one patient (2.3%) had bilateral ONA. The most common cause of trauma resulting in ONA was a metallic object (8; 18.2%). This study demonstrates the value of multi-sequence Magnetic resonance imaging (MRI) in the setting of unexplained vision loss when other modalities are inadequate or inconclusive.
Optic nerve avulsion is a devastating injury. Injuries caused by metallic objects were the leading cause of ONA. The presence of associated media opacities challenges the initial diagnosis of ONA. In the vast majority of cases, the vision ended as NLP, indicating permanent vision impairment.
Source: Mohammad Al Amry, Lamia AlHijji , Sahar M Elkhamary; Clinical Ophthalmology 2023:17 2633–2641
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