title: Circumferential flow of particles in the suprachoroidal space is impeded by the posterior ciliary arteries.
abstract: Microneedle injection into the suprachoroidal space (SCS) enables targeted drug delivery for treatment of posterior segment diseases. This study sought to identify and characterize anatomical barriers to circumferential spread of particles in the SCS of rabbit and human cadaver eyes. These barriers could make targeting specific regions within the SCS challenging. A hollow microneedle (33-gauge, 750 μm long) was used to inject fluorescent particles into albino New Zealand White rabbit eyes ex vivo at six different positions around the limbus and a limited number of conditions in vivo. SCS injections were also performed in human cadaver eyes 8 mm and 2 mm from the optic nerve (ON). Eyes were dissected and particle distribution was quantified. In rabbit eyes, injections made in the superior or inferior hemispheres (even when injected temporally immediately adjacent to the long posterior ciliary artery (LPCA)) did not significantly cross into the other hemisphere, apparently due to a barrier formed by the LPCA. The vortex veins had a minor effect on particle deposition, limited to only around the vortex vein root. In human eyes, the short posterior ciliary arteries (SPCAs) prevented circumferential spread towards the macula and ON. In conclusion, the rabbit LPCA and the human SPCA were anatomical barriers to particle spread within the SCS. Therefore, design of drug delivery protocols targeting the SCS need to account for barriers formed by anatomical structures in order for injected drug to reach target tissues.
authors.affiliation: Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Georgia Institute of Technology, Atlanta, GA, 30332, United States.
authors.forename: Bryce
authors.initials: B
authors.lastname: Chiang
authors.affiliation: School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, United States.
authors.forename: Yoo Chun
authors.initials: YC
authors.lastname: Kim
authors.affiliation: Emory Eye Center, Emory University, Atlanta, GA, United States.
authors.forename: Henry F
authors.initials: HF
authors.lastname: Edelhauser
authors.affiliation: Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Georgia Institute of Technology, Atlanta, GA, 30332, United States; School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, United States. Electronic address: prausnitz@gatech.edu.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Prausnitz
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002102:Cadaver; D002829:Choroid / Q000378:metabolism*; D019842:Ciliary Arteries / Q000378:metabolism*; D016503:Drug Delivery Systems / Q000379:methods*; D019793:Fluorescein / Q000032:analysis; D006801:Humans; D056965:Injections, Intraocular / Q000295:instrumentation / Q000379:methods*; D008845:Microinjections / Q000295:instrumentation; D008863:Microspheres; D023421:Models, Animal; D009883:Ophthalmic Solutions / Q000008:administration & dosage / Q000378:metabolism*; D010316:Particle Size; D011817:Rabbits
chemical_list: D009883:Ophthalmic Solutions; D019793:Fluorescein
keywords: Hollow microneedle; Long posterior ciliary artery; New Zealand White rabbit; Ocular drug delivery; Short posterior ciliary artery; Suprachoroidal injection