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Editors Selection IGR 14-2

Clinical Examination Methods: Blood Flow

Comment by Tae-Woo Kim on:

Spontaneous venous pulsation (SVP) is a rhythmic variation in vein diameter. Recent reports have suggested that it may have relevance with the development of glaucomatous optic neuropathy. However, the etiology of SVP remains to be better understood. To understand the SVP etiology, it is important to know when venous collapses occur within the cardiac cycle. While it has long been considered that the collapse coincides with the systole, recent reports demonstrated that the vein collapses at diastole. Moret et al. revisited this issue by observing the SVP in 12 healthy subjects using video recording. Instead of detecting the time frame when the collapse was observed, they measured the diameter of the veins near the optic disc (not within the optic disc), then determined the peaks and the troughs of the diameter. At this location, they did not find collapse of the vein in any eyes. Thus, they examined the wave forms and determined the timing of venous-diameter minima. According to their observation, there was inter-individual variation in the venous wave form: some had venous-diameter minima at systole and others had at the end of diastole. The data reconciles the previous data which reported only one type or the other. There is no clear answer for the discrepancy between the observation in this study and that in previous studies, but one possibility is that they have not measured the venous-diameter minima at the location of venous collapse but a location a bit away from that location. It is likely that the intraluminal pressure dynamics is different from that at the site of collapse. Probably the elasticity of the venous wall differs among individuals, thus the intraluminal pressure dynamics at the site of venous collapse may be transferred to the site examined in the present study in a variable way among individuals. While the study approach was novel and the result was intriguing, it is noteworthy to consider that the wave form measured in this study was not based on the collapse of the vein.

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