1. A method for measuring the intracranial pressure, ICP, in a subject, the method comprising: detecting whether spontaneous retinal venous pulsations, SRVPs, are occurring in an eye of the subject as the orientation of the head of the subject changes; identifying the orientation of the head of the subject at which SRVPs start to occur or stop occurring; and using the identified orientation of the head of the subject at which SRVPs start to occur or stop occurring to determine the ICP in the subject.