Optic nerve injury is seen either as a result of direct damage to the optic nerve or it may develop as a result of severe head or orbital trauma. A variable degree of visual impairment is reported in these patients. A comprehensive clinical and imaging workup is necessary to confirm the diagnosis.
Optic nerve injury, often termed traumatic optic neuropathy in the literature, can be divided into two main forms based on the mode of trauma. The direct injury is characterized by the primary damage to the optic nerve through compression, avulsion or transection, while the indirect injury is seen after significant trauma to the cranium and the structures surrounding the optic nerve (most commonly the orbit)    . Sharp penetrating objects are responsible for direct optic nerve injuries, while head trauma is the main mode of indirect optic nerve injury, which is much more commonly encountered in clinical practice    . The clinical presentation is not always proportionate to the severity of trauma . Decreased visual acuity, together with a defect in light perception related to the affected eye, are main signs of the optic nerve damage . Furthermore, loss of vision may be partial, but also total and lead to blindness in most severe injuries   . The onset of symptoms is almost instantaneous after trauma, but a slowly progressing course might also be noted . In the absence of an early diagnosis of treatable cases, atrophy of the nerve will occur within weeks or months, suggesting that early recognition is vital .
Optic nerve injury can be initially recognized through a detailed patient history and a careful clinical examination. In the presence of vision-related complaints, physicians should reveal if there was any recent trauma that could have led to optic nerve injury. A complete inspection of the head and a complete ocular exam (including visual acuity testing, assessment of the visual field, and direct ophthalmoscopy) are highly useful in raising clinical suspicion . One of the key procedures in solidifying the diagnosis is the use of visual evoked potentials (VEP), which uses electrical signals to determine the viability and status of the optic nerve  . In addition to clinical criteria and VEP, imaging studies are also considered as vital components in workup, particularly in the setting of indirect optic nerve injury. Computed tomography (CT) and even plain radiography are highly useful in assessing the soft tissue and skeletal structures surrounding the optic nerve, but CT is favored due to its ability to provide a more detailed view of the anatomical landmarks in the cranium    . In addition, magnetic resonance imaging (MRI), especially diffusion tensor imaging procedure, can also be employed, but only in the absence of contraindications (eg. lodged bullets or other interfering foreign bodies that are present in the endocranium)   .