Ophthalmodynamometry: a reliable method for measuring intracranial pressure

Abstract

Under physiological conditions, the pressure in the central retinal vein is equal to or higher than the intracranial pressure (ICP) because the cerebrospinal fluid (CSF) passes the sheath of the optic nerve before draining into the cavernous sinus. The optic nerve sheath is where the ICP affects the retinal venous pressure. Ophthalmodynamometry (ODM) is a useful method for determining the central retinal artery pressure. While papilledema and a lack of venous pulsations are commonly used as a vague indication of the ICP, ODM may be advantageous for determining the pressure in the central retinal vein. Until now, however, the venous pressure has never been compared with the intracranial pressure. In the present study, the pressure in the central retinal vein was recorded in 31 patients while the ICP was simultaneously being recorded for various reasons. The results demonstrate a linear correlation (r = 0.968) between the pressure in the central retinal vein and the ICP. This correlation is of great practical value since until now, reliable intracranial pressure monitoring has only been possible by invasive means, by placing a probe either in the brain parenchyma or the ventricle. Ophthalmodynamometry is useful for momentary assessment of the ICP, can easily be repeated, and may be used whenever an elevated ICP is suspected in hydrocephalus, brain tumors and after head injury. However, it is not suitable for continuous ICP monitoring.

Non-invasive Methods of Estimating Intracranial Pressure

“…The pressure from the ophthalmodynamometer is converted to mmHg and added to the baseline IOP, giving the venous outflow pressure of the central retinal vein [59]. There is a close linear relationship between venous outflow pressure and ICP [60][61][62]. Further studies are needed to determine the sensitivity and specificity of this modality.…”

Ophthalmodynamometric measurement of central retinal vein pressure as surrogate of intracranial pressure in idiopathic intracranial hypertension

“…These techniques are invasive, and carry the risk of complications such as infections and damage to the neural structures. Since it is, therefore, desirable to have a non-invasive method to estimate the intracranial pressure, and based on a previous report about the use of a modified type of ophthalmodynamometry for assessment of the intracranial pressure [1,2], it was the purpose of the present report to describe a patient in whom non-invasive determination of the central retinal vein pressure allowed an estimation of an elevated cerebrospinal fluid pressure.…”

The Role of Cerebrospinal Fluid Pressure in Glaucoma Pathophysiology: The Dark Side of the Optic Disc

“…47 When CSF pressures are above 10 mm Hg, a strong linear relationship exists between CSF pressure and the minimum IOP required to induce retinal vein pulsation [venous pulsation pressure (VPP)]. The VPP has been used to gauge CSF pressure in subjects with elevated CSF pressure, 48,49 and it had been proposed that absent spontaneous venous pulsation may indicate an appropriately counterbalanced CSF pressure, and hence be a positive prognostic sign in glaucoma. 50 The use of VPP to measure low CSF pressure seems limited as studies in dogs found that as CSF pressure fell below 7 mm Hg the VPP remained constant at 15 mm Hg (Fig.…”