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Altered Retrobulbar Hemodynamics in Patients Who Have Transient Monocular Blindness Without Carotid Stenosis

Background and Purpose— This study was to evaluate the retrobulbar hemodynamics in patients who have transient monocular blindness (TMB) without carotid stenosis. Methods— Fifty-nine patients who have TMB without carotid stenosis were studied along with 59 age- and sex-matched controls. Color Doppler–imaging was used to study the retrobulbar hemodynamic by measuring the flow velocities (peak-systolic velocity, and end-diastolic velocity), vascular resistance indices (pulsatility index, and resistance index) in central retinal arteries, short posterior ciliary arteries, and ophthalmic arteries. The patients were divided into 2 groups according to the attack frequency: group 1 (occasional TMB, 2 or fewer attacks, 26 patients) and group 2 (frequent TMB, 3 or more attacks, 33 patients). Results— The risk factors for atherosclerosis were similar between the cases and controls. The means of end-diastolic velocity were significantly lower in central retinal arteries and ophthalmic arteries, and the pulsatility index and resistance index were significantly higher in all the 3 retrobulbar vessels in TMB patients than for the controls. The differences between patients and controls were greater for the group-2 patients. Conclusion— Patients who have TMB without carotid stenosis had altered retrobulbar hemodynamics with a generalized increase in vascular resistance in the retrobulbar arteries. The role of venous hypertension as an etiology needs further study.