Abstract
Purpose :
The suprachoroidal space (SCS) has been studied as a potential space for drug delivery and gene therapy. Previously described techniques for suprachoroidal injection include a custom-made needle with a microinjector, microcatheter insertion through an ab externo scleral incision, and hypodermic needles requiring high degree of skill to target the SCS. Recent techniques describe a customized 26 or 27-gauge needle with a stopper made of either a silicone tube or plastic sheath of an intravenous catheter cut sufficiently to expose only 1.0 mm of the needle. The purpose of our work is to test the site of drug delivery to SCS via a modified version of this technique using a much thinner needle.
Methods :
Human cadaveric eyes were inflated with normal saline through optic nerve stump using a 30-gauge needle to maintain a normal intraocular pressure. The globe was fixated and stabilized to a thermocol mold. A 32-gauge hypodermic needle (length 4 mm, diameter 0.26 mm, TSK STERiJECT®, Japan) attached to a 1-cc syringe was used to deliver triamcinolone 40mg/mL (Amneal Pharmaceuticals). After confirming the injection of undiluted drug through the needle, it was mixed with indocyanine green (ICG) dye to aid in visualization of site of delivery under the microscope. As previously described, a buckle (silicone band #240, Mira Inc., Uxbridge, MA, USA) was used as a stopper to expose the terminal 1 mm of the needle, which was confirmed with a caliper. The drug was injected with the needle perpendicular to the sclera 4 mm from the limbus with a sufficient pressure to create a dimple on the sclera. The eye was then hand cut to visualize the drug delivery site.
Results :
Our results show that using this approach, it is possible to use a custom-made 32-gauge needle (Figure 1) to inject triamcinolone formulation mixed with ICG into the SCS consistently with a circumferential spread to the back of the eye, as seen in microscopic images of cross-section of the human cadaveric eye at the site of injection (Figure 2). Also, the shorter needle length aided in triamcinolone delivery through the thin 32-gauge needle consistently, as per the Poiseuille’s equation.
Conclusions :
Our work confirms that this technique allows a minimally invasive method for precise and controlled delivery of triamcinolone via a thin hypodermic needle to the posterior segment successfully and reliably.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.