Orbital Magnetic Resonance Imaging Demonstrates Better Contact between the Gas and Anterior Inferior Retina in Side versus Face-Down Position

Can wall shear-stress topology predict proliferative vitreoretinopathy localization following pars plana vitrectomy?

We numerically study the fluid dynamics of oil tamponade in models of vitrectomized eyes prompted by a subset of daily activities corresponding to movements on the horizontal plane with the patient in a standing position. Bulk flow features are related to near-wall flow topology and transport at the retinal surface through a wall shear-stress-based analysis. Proliferative VitreoRetinopathy (PVR) is the leading cause of retinal re-detachment occurring in about 20% of all cases due to the accumulation of inflammatory cells in discrete retinal regions. Signalling soluble mediators stimulate inflammatory cells' chemotaxis and studying their distribution across the retinal surface may acquire clinical relevance. In all the investigated cases, persistent and elongated regions along the retina, potentially prone to accumulate chemo-attractants and cells are observed. Gradients of soluble inflammation mediators present in the aqueous are known responsible for the so-called epithelial-mesenchymal transition that initiates PVR and favours recurrent retinal detachment prompting the proliferation of inflammatory cells with collagen matrix deposition and its contraction. The surgical apposition of encircling scleral buckling elements, known for over a century to influence PVR formation and localization, modifies the attracting regions, possibly causing an accumulation of molecules and cells along approximately vertical lines that follow the rising menisci due to the cerclage indentation. The resulting spatial pattern is compatible with clinical observations. This study may open toward rational analyses of near-wall transport to predict PVR pathogenesis by relating biochemical accumulation in certain areas of the retina to clinical conditions.

DO DAILY ACTIVITIES AFFECT GAS TAMPONADE‒RETINA CONTACT AFTER PARS PLANA VITRECTOMY?: A Computational Fluid Dynamics Study

PURPOSE

To calculate the retinal surface alternatively in contact with gas and aqueous because of fluid sloshing during daily activities such as ocular saccade, turning the head, standing up, and being a passenger of a braking car.

METHODS

Fluid dynamics of aqueous and gas tamponade was reproduced using computational methods using the OpenFOAM open-source library. The double-fluid dynamics was simulated by the volume of fluid method and setting the contact angle at the aqueous-gas-retina interface.

RESULTS

Sloshing increased the retinal surface in contact with aqueous by 13% to 16% regardless of fill rate and standing up determined the largest area of wet retina, followed by car braking, head rotation, and ocular saccade ( P < 0.001). All activities except the ocular saccade determined a significant increase in the surface of retina in contact with the aqueous ( P < 0.005). Car braking induced the highest shear stress (6.06 Pa); standing up determined the highest specific impulse and saccade the lowest.

CONCLUSION

Daily activities instantaneously reduce the amount of retina consistently in contact with gas tamponade and increase shear stress giving aqueous a potential access to the subretinal space regardless of patients' compliance.