ICP correlates with intraocular pressure (IOP) but seems to lack the accuracy necessary for close management of intracranial pressure in the acute posttraumatic period.Papilledema, or the swelling of the optic disc, can be a reliable sign that ICP is elevated. Unlike other conditions that may result in the swelling of the optic disc, it is in the case of papilledema that vision may go largely unaffected. Causes of abnormal intracranial pressure
Increased ICP
Causes of increased intracranial pressure can be classified by the mechanism in which ICP is increased:

Mass effect such as brain tumor, infarction with edema, contusions, subdural or epidural hematoma, or abscesses all tend to deform the adjacent brain. Generalized brain swelling can occur in ischemic-anoxia states, acute liver failure, hypertensive encephalopathy, hypercarbia (hypercapnia), and Reye hepatocerebral syndrome. These conditions tend to decrease the cerebral perfusion pressure but with minimal tissue shifts. Increase in venous pressure can be due to venous sinus thrombosis, heart failure, or obstruction of superior mediastinal or jugular veins. Obstruction to CSF flow and/or absorption can occur in hydrocephalus (blockage in ventricles or subarachnoid space at base of brain, e.g., by Arnold–Chiari malformation), extensive meningeal disease (e.g., infection, carcinoma, granuloma, or hemorrhage), or obstruction in cerebral convexities and superior sagittal sinus (decreased absorption). Increased CSF production can occur in meningitis, subarachnoid hemorrhage, or choroid plexus tumor.
Furthermore, the brain adjusts to the new level of carbon dioxide after 48 to 72 hours of hyperventilation, which could cause the vessels to rapidly dilate if carbon-dioxide levels were returned to normal too quickly. Hyperventilation is still used if ICP is resistant to other methods of control, or there are signs of brain herniation, because the damage herniation can cause is so severe that it may be worthwhile to constrict blood vessels even if doing so reduces blood flow. ICP can also be lowered by raising the head of the bed, improving venous drainage. A side effect of this is that it could lower pressure of blood to the head, resulting in a reduced and possibly inadequate blood supply to the brain. Venous drainage may also be impeded by external factors such as hard collars to immobilize the neck in trauma patients, and this may also increase the ICP. Sandbags may be used to further limit neck movement. Medication
In the hospital, the blood pressure can be increased in order to increase CPP, increase perfusion, oxygenate tissues, remove wastes, and thereby lessen swelling. Since hypertension is the bodys way of forcing blood into the brain, medical professionals do not normally interfere with it when it is found in a person with a head injury.