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

Purpose 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. Methods Indocyanine 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. Results Volumes 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