My eye doctor told me that papilledema (i don't have) often accompanies visual symptoms (vision loss, photopsia) caused by brain tumors. why is this?

Papilledema: Papilledema is a clinical finding doctors use to help decide if more testing is needed. It can be a sign of increased pressure inside the head. Sometimes brain masses/tumors can take up space in the head that cause an increase in pressure. This pressure may be evidenced on examination as papilledema, thus signalling the provider to perform imaging studies.

Papilloedema: Papilloedema describes swelling of the optic disc which may be reflective of elevated intracranial pressures. Elevated intracranial pressures can be caused by various different problems one of which is a brain tumor, but there are many other causes as well.

Caused by high press: Increased intra-cranial(inside the skull bones) pressure, expected from a brain tumor often results in papilledema. Your eye doctor can address all these questions for you.

Eye = external CNS: The eye is the only externalized part of the central nervous system. Papilledema, swelling of the optic disc, is due to elevated intracranial pressure (icp) at the level of the lamina cribrosa, where the intraocular pressure (iop), if lower than the icp, permits swelling of the nerve fiber layer. Brain tumors or idiopathic intracranial hypertension (iih) can cause papilledema and visual loss.

Disk edema: Because of the anatomy and direct communication of the cerebrospinal fluid around the optic nerve.

Papilledema: The brain is encased within the skull and cerebral spinal fluid(csf). There is little to no give from the bones of the skull. If a tumor takes up space the pressure inside the skull increases. The optic nerves are extensions of the brain and they are also enclosed in a sheath and surrounded by csf. When the pressure in the head increases it also increases in the optic nerve which cause it to swell.