ICP & Outflow Study

Inclusion Criteria: * Males or female between the ages of 18 and 80 (inclusive). * Able to understand the study and give informed consent. * Willing, able and available to participate in all aspects of the study. * Able to undergo accurate tonography. * Diagnosis of Idiopathic intracranial hypertension (IIH) or suspected diagnosis of IIH as determined by a consultant subspecialist neurologist or neuro-ophthalmologist. Control group will only include: * Individuals requiring lumbar puncture as part of their standard care for reasons other than suspected raised intracranial pressure e.g. for cerebrospinal fluid (CSF) sampling to analyse oligoclonal bands or other conditions necessitating lumbar puncture for diagnostic/prognostic purposes. * Individuals suspected of having a raised intracranial pressure but, upon measurement of the opening pressure, are found to have an intracranial pressure within normal limits.\* * In this study, where there are considered to be signs of raised intracranial pressure as judged by a consultant neuro ophthalmologist or neurologist, in combination with an opening CSF pressure 20cmH2O or greater, this will be taken as a raised intracranial pressure. Normal CSF pressure is taken as 19cmH2O or lower. In asymptomatic patients, pressures of up to 25cmH2O will be considered normal. Exclusion Criteria * Under 18 or over 80 years of age. * Diagnosis of ocular hypertension (ocular hypertension is defined as any individual with an intraocular pressu…