Aims: Central retinal vein pulsation is affected by intracranial pressure (ICP), glaucoma and venous pathology. Its genesis is poorly understood with most models suggesting that intraocular pressure (IOP) fluctuation dominates the rhythm of venous pulsation, however this has not been explored experimentally. We planned to measure the timing of central retinal vein pulsation with respect to intraocular pressure pulse.
Methods: Video recording of the optic disc vessels and movement of Goldmann applanation mires while recording the cardiac cycle with a pulse oximeter probe was undertaken in 10 subjects from a general ophthalmic clinic. The timing of the variation in intraocular pressure and retinal vein diameter from onset of the oximeter signal were expressed as a percent of the cardiac cycle.
Results: Minimum vein diameter occurred at mean 40msec (sd 47) after minimum IOP in 10 subjects with mean cardiac cycle length of 866msec (sd 132), the delay representing 4% (sd 5.1, 95% CI 0.3% – 8%) of the mean cardiac cycle. Maximum vein diameter occurred an average of 5 msec after maximum IOP (sd 57) representing 1% (sd 6.9, 95% CI -4% - 6%) of the mean cardiac cycle.
Conclusion: During venous pulsation, the venous collapse occurred in time with ocular diastole and dilatation in time with systole. This is contrary to prior conceptual understanding. Our results suggest that the intracranial pulse pressure may be of equal importance to IOP pulse pressure in producing venous pulsation.