Traumatic Optic Nerve Damage
Optic nerve damage resulting from injury (trauma) is divided into two categories:
(i) Direct traumatic optic nerve neuropathy and
(ii) Indirect traumatic nerve neuropathy
Direct trauma to the optic nerve encompasses penetrative injury to the eye by objects or bone fragments that transect the optic nerve fibers. The point of penetrative injury can be obscured by swelling and redness in the conjunctiva. The optic nerve may also suffer direct trauma as a result of ocular or cranial surgery (to treat the primary trauma, e.g. head injury following a car crash). Penetrative injury to the chiasma by a bone fragment, say, or damage to the blood vessels supplying it will also result in visual impairment (if not total loss of vision). Another form of direct trauma affecting the optic nerve may result from a crush injury (e.g. a displaced cranio orbital fracture).
Indirect trauma to the optic nerve can occur through transmitted forces in head injury; often to the forehead. It may result in traumatic loss of vision without any visible damage to the eye or optic nerve. A frequent cause of indirect optic nerve trauma is blunt force trauma to the orbit of the eye; mid facial trauma and frontal bone damage. Indirect injury to the optic nerve can arise by stretching or tearing forces.
In addition to direct damage to the optic nerve itself, reduction of the blood supply to the nerve is also a major cause of injury. Also physical compression of the nerve by proximal bruising or bleeding will also result in damage.
The incidence of traumatic optic neuropathy is estimated as 2.5% in both mid facial injury and closed head injuries.
Treatment options will depend on the nature and location of the damage to the optic nerve and other complicating medical conditions sustained at the same time. It may involve treatment with steroids and antioxidants or a surgical decompression of the optic nerve.