Ophthalmodynamometry is a method used to determine the pressure in the central retinal artery. It is measured by increasing the intraocular pressure (IOP) by exerting a standardized pressure on the globe while observing the optic nerve head. Ophthalmodynamometric pressure (ODP) is the minimum IOP at which the central retinal artery intermittently collapses, that is, pulsates. Measurement of ODP is important in the assessment of ocular, orbital, and neurologic diseases.
Definition of OPHTHALMODYNAMOMETRY
: measurement of the arterial blood pressure in the retina
OPHTHALMODYNAMOMETRY - A RELIABLE METHOD FOR NON-INVASIVE MEASUREMENT OF INTRACRANIAL PRESSURE
M. Motschmann*, C. Müller*, M. Schütze**, R. Firsching**, W. Behrens-Baumann*
Background: The pressure within the central vein depends on the intracranial pressure (ICP), because the optic nerve is surrounded by cerebrospinal fluid in its sheath. When the vein collapses or pulsates, ICP is higher than or equal to the pressure within the optic nerve. The first to describe this phenomena was Baurmann in 1925. He recommended to measure the pressure of the central vein to assess the intracranial pressure. However, his idea has never been verified yet. Based on his theoretical supposition we registered the pressure of the central retinal vein by non-invasive ophthalmodynamometry (ODM) and compared the findings with the results of conventional invasive ICP measurement.
Material and methods: 55 patients with suspected hydrocephalus, head injuries or other disorders with increased ICP were recruited to the study. In all patients, ICP was recorded continously for a minimum of 24 hours with intraventricular catheters or epidural probes. ODM was performed in all patients during ICP measurement. The findings were compared with the results of conventional invasive ICP measurement.
Results: The pressure of the central retinal vein correlates well with the ICP (r>0,9).
Discussion: ODM requires some cooperation from the non-comatose patient. In comatose patients it is possible to perform ODM as long as the eyelids can be retracted. Usually however, pupils need to be dilated with mydriatic agents, which may be hazardous in comatose patients. ODM should not be performed in cases of high myopia and previous intraocular surgery. As registration is only a momentary assessment, ODM is not suitable for continous monitoring. However ODM is a useful screening method in all cases of presumed ICP elevation.
Ok, I am starting to have a sense of what ophthalmodynamometry is. Still not sure how to evaluate that study. I wish we had full papers on all of these too, not the abstracts.
CCSVI has been compared to idiopathic intracranial hypertension, which is usually associated with high intracranial pressure but can sometimes exist at normal pressure.
Wasn't Dr. Diana asking for people's opening lumbar tap pressure measurements, if we know them? That would be an indicator of normal or high intracranial pressure.
Also this gets into Dr. Tucker's demonstration of how reflux can create focal points of hypertension when the two waves combine, despite otherwise normal pressure.
MrSuccess, we have large extracranial collaterals, not intracranial. But they might still have teeny-tiny equipment in Germany.