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Abstract
Objective
Transient monocular blindness (TMB) attacks may occur during straining activities that impede cerebral venous return. Disturbance of cerebral and orbital venous circulation may be involved in TMB.

Methods
Duplex ultrasonography and Doppler-flow measurement of jugular and retrobulbar veins were performed in 134 consecutive patients with TMB and 134 age- and sex-matched control subjects. All recruited patients received thorough examinations to screen for possible underlying causes.

Results
Of the 134 patients with TMB, 48 patients had ipsilateral carotid arterial lesion and 7 patients had TMB attack(s) caused by cardiac embolism. Of the remaining 79 patients with undetermined cause, 46 had 3 or more TMB attacks (undetermined-frequent group) and 33 had fewer than 3 attacks. In comparison with the control subjects, the TMB patients had greater frequencies of jugular venous reflux (57 vs 30%; p < 0.0001; odds ratio [OR]: 3.079, 95% confidence intervals [CI]: 1.861–5.096) and flow reversal in the superior ophthalmic vein (RSOV; 37 vs 9%; p < 0.0001; OR: 6.052, CI: 3.040–12.048). The undetermined-frequent group had the greatest frequencies of jugular venous reflux (74%, 34 patients; OR: 6.66, CI: 3.13–14.17) and RSOV (59%, 27 patients; OR: 6.51, CI: 3.12–13.58). Of the 50 patients with RSOV, 47 (94%) had RSOV on the side of the TMB attacks.

Interpretation
The increased incidences of jugular and orbital venous reflux in TMB patients suggest that disturbance of cerebral and orbital venous circulation is involved in the pathogenesis of TMB, especially among patients with frequent attacks of undetermined cause. Ann Neurol 2008