The symptoms are due to the tumor growing and pressing on the optic nerve and nearby structures. Symptoms may include:

• Involuntary eyeball movement
• One or both eyes may bulge outward
• Squinting
• Vision loss in one or both eyes
  • Leads to eventual blindness
  • May be a loss of peripheral vision or vision loss may be more general

The patient may show symptoms of diencephalic syndrome, which includes delayed growth, loss of appetite and body fat, daytime sleeping and decreased memory and intellectual function.

A neurologic examination reveals a loss of vision in one or both eyes. There may be changes in the optic nerve, including swelling or scarring of the nerve, or paleness and atrophy of the optic disc.

The tumor may extend into deeper locations of the brain. There may be signs of increased pressure within the brain (intracranial pressure). There may be signs of neurofibromatosis type 1 (NF1).

The following tests may be performed:

• Cerebral angiography -- often not necessary, but if used, it shows a space-occupying mass
• Head CT scan or MRI of the head -- confirms the diagnosis and the exact location of the tumor
• Tissue removed from the tumor during surgery or CT scan-guided biopsy -- examined to confirm the exact type of tumor.
• Visual field tests -- can help determine how invasive the tumor is