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Chandler Mitchell, Alon Harris, Nicholas Marazzi, Brent A Siesky, Alice Chandra Verticchio Vercellin, Ingrida Januleviciene, Sunu Mathew, Giovanna Guidoboni; Influence of Intraocular Pressure on Retinal Venous Pulsation: a Theoretical Approach. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4557.
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© ARVO (1962-2015); The Authors (2016-present)
Elevated intraocular pressure (IOP) is the main risk factor for the onset and progression of glaucoma. Several studies have shown changes in the amplitude of retinal venous pulsation as a function of IOP. In this analysis, we utilize a mathematical model to quantify the influence of IOP on pulsation amplitudes for pressure and diameter in the central retinal vein (CRV) and retinal venules.
A validated mathematical model is utilized to simulate blood flow through the retinal vasculature along the cardiac cycle (Guidoboni et al 2014). Blood pressures (Pv and Pcrv) and vascular resistances (Rv and Rcrv) in the venules and in the CRV respectively, are computed for IOP between 15 and 30 mmHg with given arterial input pressure (Pin). Vascular resistances are set as being inversely proportional to the 4th power of the vessel diameter. Pulsation amplitudes are defined as the difference between maximum and minimum values in the cardiac cycle and denoted as Pv, Pcrv, Rv and Rcrv.
The Pin is a given function of time, whose mean value equals 2/3 of the mean arterial pressure, for systemic systolic/diastolic blood pressures of 120/80 mmHg (Fig 1a). The computed Rv and Rcrv decrease during systole and increase during diastole (Fig 1b,c), indicating an increased likelihood of venous collapse during the diastolic portion of the cardiac cycle. For IOP<20mmHg, pulsation amplitudes are nearly constant in both venules and the CRV. For IOP>24mmHg, pulsation amplitudes are attenuated by IOP elevation in both venules and the CRV. Between 20 and 24 mmHg, pulsation amplitudes in the venules increase with IOP elevation, possibly due to fluid system hypersensitivity within this specific range of IOP (Fig 2).
Our analysis shows that the amplitude of retinal vein(s) pulsation changes with specific levels of IOP and dependence on the diastolic segment of the cardiac cycle. A possible critical range of IOP combined with blood pressure thresholds may alter venous compartment homeostasis and influence glaucoma susceptibility.
This is a 2020 ARVO Annual Meeting abstract.
FIGURE 1. (a) Arterial input pressure waveform; (b) Rcrv waveform; (c) Rv waveform. Black vertical line: beginning of systole; Red vertical line: beginning of diastole.
FIGURE 2. (a) Rv vs IOP; (b) Rcrv vs IOP; (c) Pv vs IOP; (d) Pcrv vs IOP. Pulsation amplitudes are defined as the difference between maximum and minimum values in the cardiac cycle and denoted as Pv, Pcrv, Rv and Rcrv.
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