Analysis of Retinal Vessel Pulsations with Electrocardiographic Gating

Abstract

Purpose The origin of retinal venous pulsations has been a matter of debate for some time. One classical explanation to the origin of these pulsations has been that the cardiac cycle induces systolic peaks in the intraocular pressure (IOP) which leads to decreases in retinal vein diameters. Recently, theoretical concepts have been published which postulate that IOP changes during the pulse cycle is not the primary driving force for venous pulsation, and hence, predict that the retinal vein diameter is indeed reduced during IOP diastole. The aim of the study was to test this hypothesis in a clinical trial. Subjects and Methods Continuous IOP and retinal vessel analyser (RVA) measurements were taken from 21 subjects, ages 20 to 30 years, with no known ophthalmologic diseases, while connected to a standard electrocardiograph (ECG). With this methodology, average and synchronised curves for the pulse cycle of IOP and retinal vessel pulsations were calculated for each subject. Each pulse cycle was standardised to 50 timepoints, which enabled direct phase shift comparisons. Results All subjects showed comparable results. Close to the optic disc (within 0 to 1.5 optic disc diameters away from the disc), retinal arteries led with the first peak at the 16/50 pulse cycle position, followed by IOP peak at the 23/50 cycle position, and then by veins at the 26/50 cycle position. Conclusion The present method indeed shows that retinal veins do not collapse when the IOP is highest, on the contrary, IOP and retinal vein diameters seem to be in phase, which lends support to the hypothesis that IOP is not the major driving force of the retinal vein pulsations.

Assessment of retinal vein pulsation through video-ophthalmoscopy and simultaneous biosignals acquisition

“…The results of the proposed approach show that the estimated Tvc values are in agreement with the results published in the papers, which use the ECG signal as a trigger (the blue part in Fig. 9 ) [ 7 , 12 , 13 ]. Shortly, Chen et al [ 12 ], in 1994, used ECG to trigger fundus camera acquisition in 8 increasing delays after the R-wave.…”

“…They evaluated 12 healthy subjects. Bollinger et al [ 7 ] in 2020 took advantage of a commercially available RVA device (Imedos UG, Jena, Germany) and connected this retinal camera with an ECG device for simultaneous acquisition. The diameter of the vessel was also extracted using the RVA software.…”

“…The IOP cycle and arterial cycle delay with respect to the R-wave do not need to be the same for each subject, and, of course, the precision of these delays is limited. Here we used delays, which were inferred from a study by Harazny et al [ 26 ] The recent study by Bollinger et al [ 7 ] showed that the delay between the R-wave and IOP beginning is at 21° and the peak is at 165°. This is an almost 50 ° difference from the values in Harazny et al If we consider this difference, then we would get more comparable results with IOP-based studies based on IOP [ 8 , 9 ].…”

“…However, there is one question that remains open: what is the timing or phase of SVP during the cardiac cycle? Some studies have been published on this topic [ 7 – 9 , 11 , 15 ], but the results are not uniform. The importance of this parameter could arise when considering ocular diseases associated with changes in blood flow (e.g.…”

How latanoprost changed glaucoma management

“…Additionally, it has been reported that elevated IOP did not induce retinal vein collapse. Moreover, IOP and retinal vein diameters seem to be in phase, which may suggest the IOP is not the major driving force of retinal vein pulsations (Bollinger et al, 2020).…”