Ocular barriers to transscleral drug delivery, and, Pharmacokinetics of an episcleral implant

The eye presents several anatomic and physiologic barriers that pose a major challenge for targeted drug delivery. The primary causes of vision impairment and blindness result from posterior segment diseases and corneal diseases [1]. To tackle these sight-threatening diseases, a number of therapeutic methods have been investigated, ranging from topical eye drops to injections and implants. Thus, the development of effective delivery systems depends upon the understanding of how the ocular barriers affect the pharmacokinetics of drugs. In Part 1, investigation of the barriers to transscleral drug delivery was performed in a rabbit model, and the model demonstrated that the conjunctival lymphatic and blood vessels may be a predominant barrier to the delivery of triamcinolone acetonide to the vitreous. In Part 2, the pharmacokinetics of a cyclosporine episcleral implant for high-risk penetrating keratoplasties was also studied, and the implant was safe and effective at delivering therapeutic levels to the cornea and surrounding tissues.