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M. Golzan, S. L. Graham, J. Leaney, A. P. Avolio; Relationship Between Retinal Venous Pulsatility and Intraocular Pressure Changes. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2675.
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Spontaneous retinal venous pulsations (SRVP) result from an interaction between intraocular pressure (IOP), retinal venous pressure (RVP) and intracranial pressure (ICP). With elevated ICP, raised RVP or reduced IOP, the intravascular pressure gradient across the prelaminar and retrolaminar portions of the central retinal vein decreases, leading to cessation of SRVP. This study examined the amplitude of SRVP and its relationship with IOP in retinal veins near the optic disc.
10 healthy subjects (35 ±10yrs) with no history of eye disease, a normal fundus on ophthalmoscopy with no vascular changes or signs of raised ICP were included. Baseline IOP/central corneal thickness (CCT) was measured and then SRVP recorded using the Dynamic Retinal Vessel Analyser (Imedos). IOP was lowered using Iopidine 0.5% and measured every 15 minutes, followed by dynamic recording of SPRV for 100 seconds - inferotemporal vein 1DD from optic disc. Mean SRVP was determined for a 20 sec period of stable recording within each sample at the same site on the vein. The blood pressure and heart rate were tracked continuously throughout (Finipress). RVP was assumed to be constant. The response to Timolol 0.5% was also tested in 2 subjects.
SRVP decreased in all subjects with reduction of IOP, but pulsations remained visible at the disc and measurable in the adjacent retinal vein. Group mean peak to peak SRVP was 10.75±4.9 um at baseline and reduced to 3.26±1.28 um after 45 minutes (p<0.0001). IOP fell from 15.5±2.5 mmHg to 10.8±2.9 mmHg over the same period (p<0.005). Mean venous diameter (155 microns), mean blood pressure (103 mmHg) and mean heart rate (74 bpm) did not change significantly with Iopidine application. Similar changes were observed with Timolol suggesting this is not simply a local drug effect on the ocular circulation.
The findings support previous theories that suggest SRVP occurs due to a pressure gradient over the central retinal vein. SRVP can be reduced by manipulation of IOP downwards with medical treatment. Using this concept further experiments could be designed to extract an index between SRVP and ICP and possibly provide a novel method for predicting ICP non-invasively.
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