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Hydrodynamics of Intravitreal Injections into Liquid Vitreous Substitutes

Biomedical Research Centre at Moorfields Eye Hospital, NHS Foundation Trust and UCL Institute of Ophthalmology, National Institute for Health Research (NIHR), London EC1V 9EL, UK
School of Pharmacy, University College London, London WC1N 1AX, UK
Department of Mechanical Engineering, University College London, London WC1E 7JE, UK
Author to whom correspondence should be addressed.
Pharmaceutics 2019, 11(8), 371;
Received: 13 June 2019 / Revised: 19 July 2019 / Accepted: 22 July 2019 / Published: 1 August 2019
(This article belongs to the Special Issue Hyaluronic Acid for Biomedical Applications)
Intravitreal injections have become the cornerstone of retinal care and one of the most commonly performed procedures across all medical specialties. The impact of hydrodynamic forces of intravitreal solutions when injected into vitreous or vitreous substitutes has not been well described. While computational models do exist, they tend to underestimate the starting surface area of an injected bolus of a drug. Here, we report the dispersion profile of a dye bolus (50 µL) injected into different vitreous substitutes of varying viscosities, surface tensions, and volumetric densities. A novel 3D printed in vitro model of the vitreous cavity of the eye was designed to visualize the dispersion profile of solutions when injected into the following vitreous substitutes—balanced salt solution (BSS), sodium hyaluronate (HA), and silicone oils (SO)—using a 30G needle with a Reynolds number (Re) for injection ranging from approximately 189 to 677. Larger bolus surface areas were associated with faster injection speeds, lower viscosity of vitreous substitutes, and smaller difference in interfacial surface tensions. Boluses exhibited buoyancy when injected into standard S1000. The hydrodynamic properties of liquid vitreous substitutes influence the initial injected bolus dispersion profile and should be taken into account when simulating drug dispersion following intravitreal injection at a preclinical stage of development, to better inform formulations and performance. View Full-Text
Keywords: hydrodynamics; hyaluronic acid; vitreous; intravitreal injection; distribution; viscosity; surface tension; density hydrodynamics; hyaluronic acid; vitreous; intravitreal injection; distribution; viscosity; surface tension; density
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Henein, C.; Awwad, S.; Ibeanu, N.; Vlatakis, S.; Brocchini, S.; Tee Khaw, P.; Bouremel, Y. Hydrodynamics of Intravitreal Injections into Liquid Vitreous Substitutes. Pharmaceutics 2019, 11, 371.

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