The suprachoroidal space as a route of administration to the posterior segment of the eye

Abstract

The suprachoroidal space (SCS) is a potential space between the sclera and choroid that traverses the circumference of the posterior segment of the eye. The SCS is an attractive site for drug delivery because it targets the choroid, retinal pigment epithelium, and retina with high bioavailability, while maintaining low levels elsewhere in the eye. Indeed, phase III clinical trials are investigating the safety and efficacy of SCS drug delivery. Here, we review the anatomy and physiology of the SCS; methods to access the SCS; kinetics of SCS drug delivery; strategies to target within the SCS; current and potential clinical indications; and the safety and efficacy of this approach in preclinical animal studies and clinical trials.

Keywords: Macular edema; Microneedle; Ocular drug delivery; Ophthalmic targeting; Posterior segment of the eye; Suprachoroidal space; Uveitis.

Copyright © 2018 Elsevier B.V. All rights reserved.

Figures

Figure 1

Diagram of eye before and after suprachoroidal space (SCS) injection. (a) Diagram of eye with relevant anatomy labeled. Insets show before and after SCS injection. (b) Histology of ex vivo porcine eye immediately after microneedle injection of fluorescent particles into SCS.

Figure 2

Diagram of eye highlighting routes of administration to the posterior segment of the eye. Intravitreal injection enables delivery to the posterior segment and is the current gold standard. The SCS can be accessed by ab interno surgical technique, by sclerotomy with subsequent micro-cannulation, or by microneedle injection to the SCS.

Figure 3

Photographs of microneedle. (a) Photograph of 1½ inch, 30 gauge hypodermic needle (left) and microneedle (right). Reproduced with permission, Gary Meek, Georgia Tech. (b) Magnified photograph of microneedle. Scale bar is 1 mm.

Figure 4

Diagram of proposed clearance route kinetic regimes. (A) Diagram of eye pre-injection. (B) Pressure-mediated leakage through injection site and perivascular drainage routes. (C) Pressure-mediated trans-scleral movement. (D) Concentration-mediated diffusion and clearance by the choroidal vasculature.