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A model system to define injection pressure and flow characteristics during subretinal drug delivery

par Ladha, Reza ;Merveille, Benjamin;Wyns, Roland;Meenink, Thijs;Willermain, Francois ;de Smet, Marc D
Référence Investigative ophthalmology & visual science, Investigative ophthalmology & visual science (63)
Publication Publié, 2022-06-01

Abstract de conférence

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Résumé :

Purpose : The risk of retinal, RPE damage and vitreous reflux increases with increased injection pressure during subretinal injections. Using a model chamber in which injection and chamber pressure can be modulated, this study aims to identify the optimal injection characteristics for subretinal drug delivery.Methods : A 38 G outer diameter subretinal injection cannula proximally attached to a MicroDose™ Injection device filled with colored water was inserted through a 23 G valved trocar into a 38 cm3 closed chamber with a defined inner pressure generated by an external compressor. The foot pedal-controlled viscous fluid injection (VFI) modes of two different vitrectomy systems (R-Evolution™ CR from BVI-Optikon and Stellaris Elite™ from Bausch and Lomb) were used to inject the solution with an injection pressure ranging from 1 to 50 psi with predefined chamber pressures of 10 , 20 and 30 mm Hg. Each injection was recorded using a video recording system. The following parameters were analyzed : pressure recording in the model, injection pressure, velocity of the injected solution, presence of an unintentional flow after release of the foot pedal.Results : The predefined pressure recorded inside the model was constant and unaffected by the different injections pressure levels chosen on the VFI. A minimal pressure of 6 psi was needed to generate a flow inside our model. From 6 to 9 psi, the velocity of the flow was categorized as slow. Higher than 10 psi, we observed a flow with high exit velocity (figure). In all cases, a persistent flow was observed after releasing the foot pedal in VFI mode. The quantity of fluid increased when increasing the level pressure of injection.Conclusions : Increased Injection pressure are associated with less controlled, high exit velocity flow characteristics. The model appears appropriate to study flow control and its possible role in RPE loss in the context of gene therapy