Optic Nerve Head Avulsion
Optic nerve head avulsion is thought to generally result from injury to the head and/or orbit. Initially the injury may be difficult to diagnose. The vision may be profoundly impacted with no known medical or surgical therapy.
Background
Risk Factors
The risk factors for optic nerve head avulsion follow the patterns for other ocular trauma. These factors would include: male sex, motor vehicle accidents, altercations, accidental finger pokes (such as with sports), and falls.
Pathophysiology
Avulsion of the optic nerve head can occur from direct or indirect force resulting in a traumatic optic neuropathy. Direct injury to the optic nerve head, from a penetrating orbital injury, is thought to be less common. Indirect injury can be from rapid torsional force to the globe resulting in shearing at the optic nerve head. Other potential mechanisms include sudden rapid increase in introcular pressure blowing out the nerve and acute anterior displacement of the globe shearing the nerve from the globe.
Primary prevention
Prevention is focused on avoidance of potential trauma including use of appropriate eye protection for sports.
Diagnosis
In cases where the view to the optic nerve head is clear, the diagnosis can be made by indirect ophthalmoscopy. Initially in many cases the view of the optic nerve head may be obscured, such as by vitreous hemorrhage. Without a clear view B-scan ultrasonography can provide further information. MRI (contraindicated as first line imaging after trauma) and CT have low sensitivity and specificity. As OCT can be impacted by media opacities, this is often not helpful initially.
