Efficacy and safety of injecting increasing volumes into the extravascular spaces of the choroid using a blunt adjustable depth injector.

purposeTo evaluate the efficacy and safety of injecting increasing volumes into the extravascular spaces of the choroid (EVSC) in rabbit eyes in vivo using a blunt adjustable depth injector.

methodsIndocyanine green (ICG) was injected in the superior-temporal quadrant, 2 mm posterior to the limbus at increasing volumes (0.1-0.3 ml) into the EVSC of New Zealand rabbit eyes in vivo. Intraocular pressure (IOP) measurements, spectral domain optical coherence tomography (SD-OCT), fundus imaging and histology analysis were performed to assess the safety and efficacy of the injection.

resultsVolumes up to 0.3 ml were administered consistently. ICG injection was successfully monitored in vivo using infrared fundus imaging and SD-OCT. ICG was detected across the EVSC compartment, reaching the retinal pigment epithelium, optic nerve head and visual streak. Injection of 0.3 ml yielded maximal dye distribution with a coverage area of 61.8% ± 6.7% (mean ± standard error, SE) of the posterior segment. Maximal IOP elevation was recorded 5 min following injection of 0.2 and 0.3 ml ICG (+ 20.0 mmHg, + 19.4 mmHg, respectively). Twenty minutes post-injection, the IOP was < 15 mmHg in all injection volumes. No retinal detachment or hemorrhages were detected in any of the injected eyes.

conclusionsThis study demonstrates consistent and safe delivery of large volumes within the EVSC using a blunt adjustable depth injector that distributes the dye over 60% of the retinal surface. This injection system may offer a minimally invasive and easy way to deliver large volumes of pharmaceuticals into the posterior segment.