Flow velocity and pulsatility of the ocular circulation in chronic intracranial hypertension.

OBJECTIVES: The aim of this study is to examine the relationship of ocular blood flow velocities and pulsatility to intracranial pressure (ICP). METHODS: We measured arterial and venous flow velocities using color Doppler imaging (CDI) and calculated resistance indices for the central retinal (CRA) and the ophthalmic (OA) arteries from 16 patients (32 eyes) with chronic intracranial hypertension (ICH) and varying degrees of ICP and papilledema. The results were compared with normal data from 16 age-matched, healthy subjects. RESULTS: Arterial flow velocities were significantly decreased for the aggregate subject group compared with controls. A corresponding rise in arterial resistance with increasing ICP in the mild-moderate range was noted. Unexpectedly, with more severe elevations of ICP these trends reversed. CONCLUSIONS: In mild-moderate increased cerebrospinal fluid (CSF) pressure, a reduction of flow velocities may result because of increased vascular resistance. Paradoxically, in more severe chronic ICH, we hypothesize that local autoregulatory vascular changes and/or diversion of cerebral blood flow into the ophthalmic circulation may normalize these parameters. This phenomenon may partially underlie the relative sparing of visual function early in the course of pseudotumor cerebri (PTC), regardless of actual ICP levels.

Orbital color Doppler imaging in carotid occlusive disease.

OBJECTIVE: To define orbital circulation abnormalities identified by color Doppler imaging in patients with severe carotid occlusive disease. PATIENTS: Twenty-four patients referred to a hospital-based neuro-ophthalmology service with hemodynamically significant carotid occlusive disease (> 75% stenosis) were prospectively studied. Eight had signs of ocular ischemic syndrome; 12 of the 24 patients underwent endarterectomy. MAIN OUTCOME MEASURES: Peak systolic velocity of the central retinal, posterior ciliary, and ophthalmic artery and pulsatility indexes as determined by color Doppler imaging. METHODS: Color Doppler imaging was performed using a 7.5-MHz probe. Both eyes were studied in all patients and carotid duplex imaging was obtained. RESULTS: All patients with hemodynamically significant carotid occlusive disease had lower mean peak systolic velocities in the central retinal, posterior ciliary, and ophthalmic arteries and higher pulsatility indexes compared with normal control patients. Endarterectomy improved peak systolic velocities. Reversal of ophthalmic flow direction as a separate variable was unassociated with altered mean central retinal or posterior ciliary artery flow velocities. Patients with ocular ischemic syndrome may have similar orbital color Doppler imaging findings compared with patients with severe carotid occlusive disease without overt manifestations of chronic ocular ischemia. CONCLUSION: Orbital circulation is highly adaptable even when faced with severe compromise in proximal blood flow.

Color Doppler imaging of the eye and orbit.

1. The use of color doppler imaging (CDI) in ophthalmology is a new and exciting area in vascular imaging. The physiologic information obtained and the anatomy evaluated has been inaccessible by any other noninvasive or invasive technique. 2. Although CDI for ophthalmic use does not, as of this time, have FDA approval, clinical trials have begun. 3. It is our expectation that CDI will be an accurate, reproducible, noninvasive method to assist ophthalmologists in the diagnosis and treatment of patients with orbital and ocular vascular disease.

Color Doppler imaging of normal orbital vasculature.

BACKGROUND: Color Doppler imaging has become a useful adjunctive tool in diagnosing ophthalmic vascular disease. However, a paucity of information exists regarding normal values. This investigation was conducted to generate a database of normal retrobulbar circulatory parameters. METHODS: The authors prospectively studied the retrobulbar hemodynamic parameters of 53 normal eyes from 32 healthy individuals of various ages, all without risk factors for the development of systemic vascular disease. Preliminary Doppler spectral analysis was used to demonstrate normal carotid arterial, carotid siphon, and ophthalmic vascular anatomy. RESULTS: Mean hemodynamic values were recorded for each retrobulbar vessel. Diastolic blood pressure significantly correlated with ophthalmic arterial end-diastolic velocity (P < 0.05) and pulsatility index (P < 0.05). Although end-diastolic velocity significantly decreased (P < 0.05) and vascular resistance significantly increased (P < 0.05) as a function of age in the posterior ciliary and central retinal arterial circulation, no such correlation was identified in the ophthalmic artery which demonstrated significantly more hemodynamic variability among individuals (P < 0.00001). No significant differences in blood flow or vascular resistance were noted between sexes, fellow orbits, or the nasal and temporal branches of the posterior ciliary artery within individual orbits. CONCLUSION: Orbital hemodynamic parameters do not appear to be sex dependent or variable between fellow orbits. These data suggest that age and diastolic blood pressure may affect normal orbital blood flow and vascular resistance patterns. Significant interindividual variability is limited only to ophthalmic arterial blood flow.

Reversible abnormalities in the ophthalmic arteries detected by color Doppler imaging.

PURPOSE: To demonstrate dynamic, reversible abnormalities in ophthalmic artery blood flow velocity identified with color Doppler imaging (CDI) in patients with clinical findings of ocular ischemia with and without carotid artery stenosis. METHODS: One patient with ocular ischemia and normal carotid arteries had abnormal ophthalmic artery velocities demonstrated by CDI. Two other patients with reversed ophthalmic artery flow and critical internal carotid artery stenosis were studied before and after carotid endarterectomy. Peak systolic and diastolic velocities as well as pulsatility indices of ophthalmic, posterior ciliary, and central retinal arteries were calculated. RESULTS: The patient who had ocular ischemic syndrome without carotid artery stenosis showed increased ophthalmic artery velocities initially, and reversal of flow within the ophthalmic artery subsequently developed. Clinical findings and symptoms improved gradually as ophthalmic artery, posterior ciliary, and central retinal artery velocities increased. The patients with critical internal carotid artery stenosis had reversed ophthalmic artery blood flow initially which reverted to normal after carotid endarterectomy. CONCLUSION: Ocular ischemic syndrome may occur due to abnormal blood flow in the ophthalmic artery in the absence as well as in the presence of carotid artery stenosis. Flow dynamics in the ophthalmic artery and its branches can be shown by CDI to revert toward normal as the clinical findings improve spontaneously or after opening an occluded carotid artery.