Treatment of diseases of the posterior segment of the eye such as choroidal neovascularization presents a major challenge in ophthalmology. The posterior segment of the eye, including the retina, macula, and optic nerve, is difficult to access due to the recessed location within the orbital cavity.
Current drug delivery techniques to access the posterior segment of the eye include intra-vitreal injections, peri-ocular injections (i.e., subconjunctival, subtenon, or juxtascleral), and intra-vitreal implants. Drug delivery by injection into the suprachoroidal space is another technique that has recently been proposed in the treatment of posterior segment disease. The suprachoroidal space provides a potential route of access from the anterior region of the eye to the posterior region.
The iScience Surgical Ophthalmic Microcannula, or iTrack (iScience Surgical Corporation, Menlo Park, CA) is designed to access ocular structures such as schlemm's canal, subretinal space, vitreous cavity, and the suprachoroidal space. The iTrack received 510(k) clearance from the U.S. Food and Drug Administration on June 22, 2004 as a flexible microcannual for atraumatic cannulation of spaces in the eye such as the anterior chamber and posterior segment, for infusion and aspiration of fluids during surgery, including saline and viscoelastics. The microcannula incorporates an optical fiber to allow transmission of light to the microcannula tip for surgical illumination and guidance.
There is inadequate evidence regarding the clinical utility of supracoroidal injection of pharmacologic agents for the treatment of any ophthalmologic condition. Clinical outcome studies published in the peer-reviewed medical literature are needed to determine the value of this drug delivery method in the management of patients with diseases of the posterior segment of the eye.
In a pilot study, Rizzo et al (2012) evaluated the safety, feasibility, and preliminary effectiveness of suprachoroidal drug delivery with a microcatheter for the treatment of severe subfoveal hard exudates (SHE) in retinal vasculopathies. A total of 6 eyes of 6 patients with central or branch retinal vein occlusion or diffuse diabetic macular edema accompanied by massive refractory SHE underwent a single treatment with bevacizumab and triamcinolone administered to the submacular suprachoroidal space via a microcatheter introduced at the pars plana and advanced posteriorly. The main outcome measures included best-corrected visual acuity, vascular leakage, macular thickness, extent of SHE, and complications. Mean follow-up was 12 months; 3 eyes had central retinal vein occlusion, 1 had branch retinal vein occlusion, and 2 had chronic diabetic macular edema. Best-corrected visual acuity improved by greater than or equal to 2 lines in 4 eyes and remained stable in 2 eyes. At 1 month to 2 months post-procedure, SHE was almost completely resolved in all eyes and macular edema was significantly reduced. There were no surgical or post-operative complications. The authors concluded that suprachoroidal infusion of drugs can be effective in reabsorbing massive SHE. The findings of this pilot study needs to be validated by well-designed studies.
Tetz et al (2012) examined the safety and feasibility of using a microcatheter for drug delivery in the suprachoroidal space in eyes with advanced, exudative, age-related macular degeneration (ARMD) unresponsive to conventional therapy. A unique microcatheter was used to deliver a drug combination consisting of bevacizumab and triamcinolone to the submacular suprachoroidal space. A total of 21 eyes of 21 patients with choroidal neovascularization (CNV) secondary to advanced, exudative ARMD were followed over a 6-month post-procedure period. The microcatheter was successfully and atraumatically inserted into the suprachoroidal space of all eyes. No serious intra-operative or postoperative complications including suprachoroidal hemorrhages were encountered. Post-surgically, complications consisted of 1 eye experiencing a transient elevation in intra-ocular pressure at 3 months, which was medically controlled, and 2 eyes (10.5 %) with an apparent increase in nuclear sclerotic cataracts. The authors concluded that suprachoroidal drug administration was achieved without serious complication using a novel microcatheter. They noted that direct drug delivery to the choroid can potentially increase local tissue drug levels and drug effectiveness for the treatment of ARMD and other diseases associated with CNV. These preliminary findings need to be validated by further studies.