Background: The frequency of jugular venous reflux (JVR) is higher in patients with transient monocular blindness (TMB). We hypothesize that JVR influences ocular venous outflow, and resulting disturbances in cerebral and ocular venous circulation might be a cause of TMB. To substantiate this hypothesis, we aimed to demonstrate that: (1) TMB patients have vasculature changes in their retinal venules, and (2) JVR could influence ocular venous outflow, as revealed by dilated retinal venules. Methods: This study has 2 parts. The case-control study included 31 TMB patients and 31 age/gender-matched normal individuals, who all received fundus photography for retinal venule diameter comparisons. The Valsalva maneuver (VM) experiment included 30 healthy volunteers who received both color Doppler imaging of the internal jugular vein and fundus photography for retinal venule diameter measurement. Results: In the case-control study, TMB patients had a wider retinal venule diameter (184.5 ± 17.5 vs. 174.3 ± 16.2 μm, right eye, p = 0.023; 194.20 ± 24.6 vs. 176.6 ± 19.5 μm, left eye, p = 0.017), especially TMB patients with JVR. The VM experiments showed that the presence of JVR was associated with a greater increase in retinal venule diameters during VM in the subjects' right eye (14.27 ± 11.16 vs. 2.75 ± 3.51%, JVR vs. non-JVR, p = 0.0002) and left eye (10.06 ± 6.42 vs. 1.80 ± 2.03%, p = 0.0003). Conclusions: These findings provide evidence that frequently occurring JVR associated with TMB impedes ocular venous outflow, and the subsequent disturbances in ocular venous circulation may be a cause of TMB.
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