|Year : 2017 | Volume
| Issue : 2 | Page : 97-99
Optic nerve avulsion: A rare presentation of blunt trauma
Valiyaveettil Babitha, Chellappan Prasannakumary, ECK Ramesan, Kuzhippally Vlluon Raju
Department of Ophthalmology, Government Medical College, Kozhikode, Kerala, India
|Date of Web Publication||7-Aug-2017|
Department of Ophthalmology, Government Medical College, Kozhikode - 673 008, Kerala
Source of Support: None, Conflict of Interest: None
Optic nerve avulsion is one of the severe complications of blunt ocular trauma. Although a rare entity, optic nerve avulsion should be suspected in all blunt trauma cases presenting with sudden marked visual loss accompanied with dense vitreous hemorrhage.
Keywords: Blunt trauma, optic nerve, partial optic nerve avulsion
|How to cite this article:|
Babitha V, Prasannakumary C, Ramesan E, Raju KV. Optic nerve avulsion: A rare presentation of blunt trauma. Muller J Med Sci Res 2017;8:97-9
|How to cite this URL:|
Babitha V, Prasannakumary C, Ramesan E, Raju KV. Optic nerve avulsion: A rare presentation of blunt trauma. Muller J Med Sci Res [serial online] 2017 [cited 2020 Sep 24];8:97-9. Available from: http://www.mjmsr.net/text.asp?2017/8/2/97/212410
| Introduction|| |
Avulsion of optic nerve is a type of anterior optic neuropathy with very poor visual prognosis.,, In total optic nerve avulsion, visual loss is dense and complete. Visual prognosis is better in participants with partial avulsion.
| Case Report|| |
A 27-year-old male patient presented with a history of sudden loss of vision of the left eye following a fall and trivial injury with a wooden piece on left side of face. On examination, there was minimal lid edema and periorbital ecchymosis. Orbital walls were intact. Extraocular movements were full. A 2 mm partial thickness conjunctival wound with subconjunctival hemorrhage was seen on the nasal side. Cornea was clear. Hyphema was present (1 mm). Pupillary examination showed Grade 3 Relative Afferent Pupillary Defect. His visual acuity was perception of light with inaccurate projection. Fundus examination revealed localized dense peripapillary hemorrage with vitreous hemorrhage overlying the optic disc [Figure 1]. Right eye was normal. Immediate ultrasonography revealed vitreous hemorrhage. High-resolution computed tomography (CT) showed partial optic nerve avulsion with intact globe contour [Figure 2]. The patient underwent Trans pars plana vitrectomy with fluid-air exchange with gas tamponade. Vision improved to 2 MCF. This visual acuity was retained at 1 year follow-up. Fundus showed glial proliferation over the optic disc suggestive of old partial optic nerve avulsion [Figure 3].
| Discussion|| |
Optic nerve avulsion is caused by blunt ocular injury or head injury. In avulsion, optic nerve is disinserted from retina, choroid, and vitreous and separated from the globe at the level of lamina cribrosa without rupture of nerve sheath and adjacent sclera. The mechanisms of optic nerve avulsion may be anterior luxation of globe, retropulsion of nerve, forced rotation of globe around its axis producing tearing of the optic nerve parenchyma without involving the optic nerve sheath or sudden explosive rise in intraocular pressure blowing nerve off the sclera into dural sheath and direct penetration of a foreign body through the medial part of the orbit into the anterior part of the optic nerve with disinsertion of dura.,,, The concussion waves arising from facial injury is conducted through the surrounding bones into the orbit and may leads to optic nerve avulsion. Common sites of optic nerve involvement in blunt trauma are intraorbital and intracanalicular parts and rarely at optic disc. The absence of myelin and supportive connective tissue septae make the axons more vulnerable to trauma at lamina cribrosa. Nerve mobility within the orbit is a predisposing factor for avulsion because it is covered only by sheaths at this level. Intracranial part of optic nerve is less involved.
Because of the close relation of retinal vasculature with optic nerve, several vascular changes can occur in optic nerve avulsion. The vasculature may be of normal pattern, tortuous, attenuated, occluded at the level of avulsion or segmentation of intravascular blood column can be seen., Rarely, central retinal artery occlusion can occur in optic nerve avulsion.
Immediate visual loss in optic nerve atrophy (ONA) may be due to damage and break of the nerve fibers. Other reasons for visual loss in ONA are secondary hematomas and edema.
In a clear media, diagnosis of the condition is very easy by fundus examination, by seeing a hole or cavity in the position of optic disc but is commonly associated with dense vitreous and retinal hemorrhage. In hazy media ultrasonography, CT scan, optical coherence tomography (OCT), and fundus fluorescein angiography can be done with less sensitivity for diagnosis.,, Ultra sonography in this case is to rule out globe rupture and show posterior ocular wall defect with a hypolucent area in the optic nerve head. CT orbit can show a complete or partial lesion of the optic nerve with a hypolucence area in nerve junction with the globe and a proximal hyperlucency due to posterior displacement of the lamina cribrosa.,, In optic nerve avulsion, noncontrast CT and magnetic resonance imaging demonstrate vitreous prolapse into the optic nerve sheath, and by spectral domain OCT and visual evoked potentials ganglion cell layer disruption can be confirmed.
In optic nerve avulsion, final visual acuity depends on the initial vision after trauma., On follow-up, in cases of total optic nerve avulsion there will not be any visual improvement, but in partial optic nerve avulsion there will be partial improvement of vision immediately after trauma and then, it remains the same. Patients with dense vitreous hemorrhage may have visual improvement following vitrectomy, but it is limited because of optic nerve disorder. The morphological changes seen in optic nerve avulsion are mainly due to fibroglial proliferation from the detached scleral outlet, which leads to partial retinal detachment localized to peripapillary area or total retinal detachment and epiretinal membrane formation (retinal glial cells and retinal pigment epithelial [RPE] cells). In mild cases, minor fibroglial proliferation and RPE hyperplasia can be seen.
| Conclusion|| |
Optic nerve avulsion should be suspected in all blunt trauma cases with sudden severe visual loss and dense vitreous hemorrhage. Unnecessary high-dose intravenous steroids can be avoided by correct diagnosis. Most of the time, it is a medicolegal issue also. In spite of poor visual prognosis and absence of specific treatment optic nerve avulsion is a diagnostic challenge in the presence of vitreous hemorrhage, because there is no additional reliable and sensitive test for diagnosis.
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[Figure 1], [Figure 2], [Figure 3]