Development and Ex-vivo Evaluation of a Novel Device to Facilitate and Standardize Intravitreal Injections in Rabbits

Rabbits are frequently used to study the pharmacokinetics and toxicology of compounds delivered into the eye as they are a translatable animal model. The aim of this study was to develop a device which facilitates and standardizes intravitreal injections in rabbits. Similar devices for intravitreal injections in humans already exist and have shown to prevent damage to the retina and lens. We hypothesized use of the new device would increase the precision of injections and results would be comparable between experienced and novice operators. Prototype devices were produced using 3-dimensional (3D) printing and trailed using a 3D-model of the eye. The final device was produced using injection-molding. Two aspects were investigated using ex-vivo rabbit eyes; (1) Location of contrast-agent-deposition within the vitreus following device-guided and freehand injections by a novice operator was analysed by magnetic-resonance-imaging (MRI). (2) The anatomical location of the needle-penetration-point following device-guided and freehand injections by one experienced and three novice operators was evaluated using histology. Our results indicate that the device can successfully be used to deliver compounds into a favourable mid-vitreal location. Following device-guided injection the contrast-agent was never located in direct proximity to the lens while this was the case in over half of freehand injections. We interpret this as a safety benefit of the device as it consistently directs the injection away from the lens. Contrary to our hypothesis the device did not lead to increased precision nor did it allow novices to achieve comparable results to an experienced operator. In conclusion, the device facilitates intravitreal injection to rabbit eyes and might offer a safety benefit as it directs the needle away from the lens. Further in vivo studies are required to evaluate the device's effects on the safety and pharmacokinetics of intravitreal injections.