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

Abstract

To 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. Indocyanine green (ICG) was injected in the superior-temporal quadrant, 2mm posterior to the limbus at increasing volumes (0.1-0.3ml) 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. Volumes up to 0.3ml 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 0.3ml 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 5min following injection of 0.2 and 0.3ml ICG (+ 20.0mmHg, + 19.4mmHg, respectively). Twenty minutes post-injection, the IOP was < 15mmHg in all injection volumes. No retinal detachment or hemorrhages were detected in any of the injected eyes. This 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.