Intracameral Puncture Lowers Intraocular Pressure and Triggers an Immune Response in the Conventional Outflow Tract

Intracameral injection is an effective delivery method for biomedical agents and therapeutics to conventional outflow tract tissues. However, the effect of intracameral injections on intraocular pressure (IOP) and aqueous dynamics has not been well characterized, warranting further investigation.

Wild type 3 to 5-month-old C57BL/6 mice were subjected to intracameral puncture (ICP; without injection of any material). Following ICP, IOP, outflow facility, aqueous production, episcleral vessel diameter, and macrophage densities were measured.

On day 1, IOP was significantly reduced by 30% (P < 0.0001, n = 25), whereas outflow facility (P = 0.31, n = 15) and aqueous production (P = 0.16, n = 9) were unchanged. As well, Schlemm's canal filtration area was unchanged, however, distal vessels were dilated (P < 0.001) at day 1 post-ICP. Correspondingly, macrophage density was significantly increased around the episcleral vessels (P < 0.0005) at day 1. Macrophage densities in Schlemm's canal and trabecular meshwork, while unchanged at day 1, were significantly increased by day 3 (P < 0.0001).

Coincident with significantly reduced IOP 1 day after ICP, there was an influx of macrophages into the distal portion of the conventional outflow tissues and a dilation of episcleral vessels, likely reducing distal outflow resistance. Our study demonstrates the importance of considering the drug delivery method to the eye due to its effects on the immune response and conventional outflow homeostasis.