Accessing the Suprachoroidal Space for Therapeutic Delivery

Safety and Efficacy of Suprachoroidal Injection of Triamcinolone in Treating Macular Edema Secondary to Noninfectious Uveitis

Introduction 

One of the leading causes of blindness throughout the world is uveitis, which predominantly results in the feared complication of macular edema. We report the safety and efficacy of suprachoroidal injection of triamcinolone acetonide in the treatment of macular edema secondary to noninfectious uveitis. 

Methodology 

This prospective, nonrandomized interventional study was conducted at Layton Rahmatullah Benevolent Trust (LRBT) Eye Hospital, Lahore, from August 2019 till July 2020. All individuals older than 18 years, nonpregnant females with a central macular thickness of >320 µm were included. Those patients with uncontrolled diabetes, immunodeficiency, or any other disease mandating systemic corticosteroid use were excluded. All patients had a detailed ocular exam one week before the treatment, and 0.1 ml of triamcinolone acetonide 40 mg/ml was injected using a 30-G hollow needle into the suprachoroidal space. After the injection, an eye patch was applied and the patient was observed for three hours. All data were documented in a preformed proforma. 

Results

A total of 30 patients were included in the study with a mean age of 38.1 ± 9.48 years. Statistically significant differences were found between central macular thickness at presentation and at one and three months of the procedure, i.e., 569.60 ± 170.396, 266.77 ± 73.127, and 208.27 ± 37.292 µm, respectively. A similar difference was observed when comparing visual acuity at baseline to visual acuity at one and three months of the procedure (p < 0.001). 

Conclusion 

The current study indicates that a single dose of suprachoroidal injection of triamcinolone acetonide for the treatment of macular edema secondary to uveitis is safe and efficacious. No rise in intraocular pressure (IOP) was observed during the study period. Significant improvements in central macular thickness and visual acuity as well as tolerability and safety of the treatment were seen in our study. Further larger-scale studies are needed to ascertain the long-term benefits of the suprachoroidal triamcinolone acetonide.

Collagenase injection into the suprachoroidal space of the eye to expand drug delivery coverage and increase posterior drug targeting

Injection into the suprachoroidal space (SCS) allows drug delivery targeted to sclera, choroid, and retina. Here, we studied SCS injection formulated with collagenase to expand drug delivery coverage and increase posterior drug targeting within SCS by breaking down collagen fibrils that link sclera and choroid in the SCS. When 1 μm latex microparticles were injected with a collagenase formulation using microneedles into the SCS of rabbit eyes ex vivo and incubated at 37 °C for 4 h, microparticle delivery coverage increased from 20% to 45% and enhanced posterior drug targeting. Collagenase concentration was optimized to 0.5 mg/mL to maximize expanded posterior delivery and minimize tissue damage. Effects of collagenase injection within SCS increased and then plateaued 4 h after injection. Simultaneous injection of collagenase and microparticles had a greater effect on expanded delivery in the SCS compared to sequential injection. Collagenase injection into the SCS of rabbit eyes in vivo was also effective to expand delivery and was generally well-tolerated, showing transiently lowered IOP, but no apparent lasting adverse effects on ocular tissues such as sclera, choroid, and retina, as determined by analyzing histology, sclera tensile strength, and fundus imaging. We conclude that addition of collagenase during SCS injection can expand drug delivery coverage and increase posterior drug targeting.

Medical and Surgical Applications for the Suprachoroidal Space

In recent years, advances in ocular imaging, drug delivery, and ophthalmic surgery have allowed for better visualization and access to the suprachoroidal space. Although previously considered as only a potential space, the suprachoroidal space may serve as a route for drug delivery to the posterior pole, an egress for glaucoma drainage devices, a location for temporary buckling, and a site for prosthesis implantation. Drugs delivered to the suprachoroidal space may achieve higher concentrations in the retina while minimizing exposure to anterior segment tissues, potentially reducing risks of glaucoma or cataracts. Finally, advanced multimodal imaging now allows not only a better understanding of the physiology of the suprachoroid, but also in vivo monitoring of pathologies and drug delivery to the suprachoroidal space. Here, we discuss the newest developments in the medical and surgical applications of this space with potential.