Custom-Made Injector for Suprachoroidal Ocular Delivery: Effect of Intraocular Pressure, Volume, and Location on the Distribution of Aqueous Solutions in Rabbits.

Purpose: Develop a custom-made injector system for delivery of aqueous solutions to the suprachoroidal space (SCS). And to test the effect of intraocular pressure (IOP), volume, and location on distribution. Methods: SCS injectors were produced in the laboratory using readily available components. Fifty 100 µL of either fluorescein sodium and/or indocyanine green (ICG) dye solutions were injected 6-mm posterior to the corneal limbus in either the superotemporal or inferonasal quadrants of the eyes of albino rabbits. Coverage of the injected dyes was documented in vivo. Distribution of 50- and 100-µL single-injection volumes was compared, as were 50-µL injections in two opposing quadrants. The vasoconstrictor endothelin-1 was injected into some eyes as a test of efficacy. To determine the possible effects of IOP on injection coverage, both eyes of 6 rabbits were injected with ICG in a crossover design with the IOPs of the eyes held manometrically at either 10 or 35 mmHg. Results: Successful SCS injections, as determined by fundus imaging, were done in more than 40 rabbit eyes [as well as 40 nonhuman primate eyes in separate studies]. One hundred microliters single injections provided better coverage than 50 µL, but the most complete coverage was with two 50-µL injections in opposite quadrants, although gaps remained. No statistically significant difference in coverage between IOPs of 10 and 35 mmHg was observed. Conclusions: Construction of a reliable custom-made injector system is feasible. IOP at the pressures measured did not appear to affect coverage of the suprachoroidally injected ICG dye solution.