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Purpose : Optic neuropathies such as normal-tension glaucoma(NTG) may be caused by pathogenic translaminar pressure difference(TLPd). This mechanistically may lead to an improper perfusion of lamina cribrosa(LC) and alter the natural biomechanics of the eye. LC perfusion parameters are difficult to estimate with non-invasive measurements and the interaction between hemodynamics and biomechanics is affected by many factors that cannot be easily isolated. We employ a mathematical virtual simulator(MVS) to disentangle biomechanical and hemodynamical factors, in particular the system response to intraocular pressure(IOP) and retrolaminar tissue pressure(RLTp) alterations. Methods : The MVS(Fig. 1b) combines i) a three-dimensional porous-media model for LC perfusion with ii) a circuit-based model for blood flow in retrobulbar and ocular posterior segments and iii) a three-dimensional elastic model to simulate the biomechanics of LC, retina, choroid, sclera and cornea. Systems i), ii) and iii) are solved using advanced computational and visualization methods (Feel++, OpenModelica). We simulate 5 different virtual situations: baseline(IOP=15,RLTp=7,TLPd=8 [mmHg]), patient1(P1,IOP=11,RLTp=10,TLPd=1 [mmHg]), patient2(P2,IOP=17,RLTp=10,TLPd=7 [mmHg]), patient3(P3,IOP=17,RLTp=3,TLPd=14 [mmHg]) and patient4(P4,IOP=11,RLTp=3,TLPd=8 [mmHg]). Results : Baseline, P2 and P4 have similar TLPd, however Fig. 1c shows a difference up to 10% in LC perfusion. Fig. 1a displays a 1.4% discrepancy in the blood pressure gradient, whereas Fig. 2 exhibits analogous LC displacements for these three cases. Thus, MVS suggests that this difference may be primarily due to hemodynamical factors. RLTp variations do not seem to have notable effects on the velocity of central retinal artery(CRA) and the central retinal vein(CRV) both pre- and post-lamina(Fig. 1d-e), whereas small fluctuations occur in the CRV velocity due to higher IOP(P2,P3). Conclusions : In the context of glaucoma, particularly NTG, the proposed MVS multi-scale approach may be employed to single out hemodynamic and/or biomechanical mechanisms involved in the pathophysiology of ocular disease. This innovation may also allow for novel findings in IOP regulation and RLTp effects in central retinal vein occlusion. This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

Purpose Improper perfusion of the lamina cribrosa (LC) may lead to severe alterations of the visual function. LC perfusion parameters are difficult to estimate with non-invasive measurements and are affected by many factors that vary among individuals and cannot be easily isolated. Here we utilize a mathematical virtual simulator (MVS) to address these challenges. Methods The MVS combines i) a three-dimensional porous-media model for LC perfusion with ii) a circuit-based model for blood flow in the retrobulbar and ocular posterior segments (Fig. 1). Systems i) and ii) are solved using advanced computational and visualization methods (Feel++). Simulation inputs may include some patient-specific factors that can be measured non-invasively, e.g. systolic blood pressure (SBP), diastolic blood pressure (DBP), intraocular pressure (IOP) and ocular geometry. Results Fig. 2a shows the MVS visualization of ocular geometry. MVS simulated LC perfusion velocities at time t = 2.4 s (green line) are shown for IOP = 15 mmHg and SBP/DBP = 100/70 mmHg (Fig. 2b), SBP/DBP = 120/80 mmHg (Fig. 2c), SBP/DBP = 140/90 mmHg (Fig. 2d). Increasing SBP and DBP leads to higher LC perfusion velocities, especially near the nasal area. MVS also simulates blood velocities in the central retinal artery and vein (CRA and CRV), as shown in Figs. 2e and 2f, respectively, which are similar to those obtained via direct Imaging modalities. Conclusions MVS may serve as an instrument to illustrate and estimate LC perfusion parameters and predict their spatial variability, thereby providing new means to address the increasing demand of information on ocular tissues that are not-easily accessible with standard investigation instruments.

The transverse spin correlations A_{x,x} and A_{y,y} have been measured in the pol{d} pol{p} -> p_spec {pp}_s pi- reaction at COSY-ANKE at 353 MeV per nucleon. Here {pp}_s denotes a proton-proton pair with low excitation energy, which is dominantly in the 1S0 state. By measuring three protons in the final state it was possible to extract events where there was a spectator proton p_spec so that the reaction could be interpreted in terms of quasi-free pol{n} pol{p} -> {pp}_s pi-. The proton analyzing power in this reaction was also deduced from this data set by averaging over the polarization of the deuteron beam. The values of A_y^p were shown to be consistent with a refined analysis of our earlier results obtained with a polarized proton incident on a deuterium target. Taking these data in combination with our earlier measurements of the differential cross sections and analyzing powers in the pol{p} p -> {pp}_s pi^0 reaction, a more robust partial wave decomposition was achieved. Three different acceptable solutions were found and the only way of resolving this ambiguity without further theoretical input would be through a measurement of the mixed spin-correlation parameter A_{x,z}.

In order to establish links between p-wave pion production in nucleon-nucleon collisions and low energy three-nucleon scattering, an extensive programme of experiments on pion production is currently underway at COSY-ANKE. The final proton pair is measured at very low excitation energy, leading to an S-wave diproton, denoted here as {pp}_s. By using a deuterium target we have obtained data on the differential cross section and analysing power of the quasi-free pol{p}n -> {pp}_s pi^- reaction at 353 MeV. The spectator proton p_sp was either measured directly in silicon tracking telescopes or reconstructed using the momentum of a detected pi^-. Both observables can be described in terms of s-, p-, and d-wave pion production amplitudes. Taken together with the analogous data on the pol{p}p -> {pp}_s pi^0 reaction, full partial wave decompositions of both processes were carried out., The interested reader should also study the paper on pizero production by D.Tsirkov et al., which has also been submitted to the arXiv

In order to establish links between p-wave pion production in nucleon-nucleon collisions and low energy three-nucleon scattering, an extensive programme of experiments on pion production is currently underway at COSY-ANKE. The final proton pair is measured at very low excitation energy, leading to an S-wave diproton, denoted here as {pp}_s. By using a deuterium target we have obtained data on the differential cross section and analysing power of the quasi-free pol{p}n -> {pp}_s pi^- reaction at 353 MeV. The spectator proton p_sp was either measured directly in silicon tracking telescopes or reconstructed using the momentum of a detected pi^-. Both observables can be described in terms of s-, p-, and d-wave pion production amplitudes. Taken together with the analogous data on the pol{p}p -> {pp}_s pi^0 reaction, full partial wave decompositions of both processes were carried out., Comment: The interested reader should also study the paper on pizero production by D.Tsirkov et al., which has also been submitted to the arXiv

International audience; Elevated intraocular pressure (IOP) can be reduced via medications modulating aqueous humor (AH) flow, but the drug efficacy varies significantly among patients. Many factors may influence drug efficacy, including mean arterial pressure (MAP) and systemic vascular resistance (sVR). Here we propose a mathematical model to theoretically investigate the individual roles played by MAP and sVR on the response to IOP-lowering medications.