Optic nerve glioma is the most common type of tumor of this nerve. While it occurs in the pediatric and adult populations, clinical manifestations typically become apparent in childhood. If symptomatic, signs include decreased visual acuity, proptosis, strabismus, and swelling of the optic disc. This tumor is strongly associated with neurofibromatosis 1 (NF1) but can exist alone. The diagnosis is based on a detailed history, eye and general exam, and imaging.
Optic nerve glioma (ONG) is the most predominant type of neoplasm of the optic nerve . These tumors are frequently unilateral and have a predilection for females . They occur sporadically although familial cases do develop in patients with neurofibromatosis 1 (NF1) as these diseases are strongly associated  . Furthermore, most ONGs occur in children while three-fourth of sufferers experience symptoms within the first decade and 90% by the age of 20 years .
The clinical presentation includes decreased visual acuity and function, progressive proptosis, and swelling of the optic disc  . Strabismus is another common feature . There is no pain associated. Some cases will suffer from acute blindness and worsening proptosis secondary to hemorrhage . Note that not all ONGs produce complaints as some are detected incidentally during routine screening in those with NF1 .
Chronic compression of the central retinal vein can result in central retinal vein occlusion (CRVO) and other severe eye pathologies .
Fundoscopy reveals pallor and swelling of the optic disc and impaired acuity  . Moreover, the eye exam demonstrates an abnormal pupillary reflex as well as visual field deficits. The latter reflects the affected optic nerve segments. For example, the involvement of the portion anterior to the optic chiasm results in a visual loss in the ipsilateral eye. Additionally, a defect in the optic chiasm causes bitemporal hemianopsia whereas a damaged segment posterior to the chiasm leads to homonymous hemianopsia.
Proptosis is apparent and may appear cosmetically disfiguring . Eye movements may also be affected .
Patients with NF-1 will exhibit skin lesions in addition to other features.
Those coming with the above clinical manifestations should be considered for optic nerve glioma. Additionally, children with NF-1 should be screened for this tumor. The workup will include a thorough history, assessment of the symptoms, a detailed ophthalmic and general physical exam, and the appropriate studies.
Magnetic resonance imaging (MRI) is the preferred diagnostic tool for optic nerve gliomas. This modality is more effective than computed tomography (CT) in characterizing the intraorbital tumor and the extent of its growth as it broadens into the chiasm   . CT scanning typically depicts lesions confined within the orbit. Note that both MRI and CT show an enlarged optic canal if present, although this finding does not necessarily indicate an intracranial extension.
MRI with gadolinium enhancement and fat saturation characterizes the extent of the lesion. Moreover, T1-weighted tumors are described as hypointense to isointense   whereas T2-weighted masses are revealed as isointense or hyperintense.
Very importantly, an ONG appears differently on imaging in patients with NF1 than it does in isolated cases . When associated with NF1, the lesion can expand into subarachnoid and subdural spaces . In individuals without NF1, imaging tends to feature diffuse fusiform expansion of the optic nerve with a bend or kink  .