Ocular Drug Delivery System

Last updated: October 2026

Delivering drugs effectively to the eye is difficult — tear dilution, blinking, nasolacrimal drainage, and the blood-ocular barriers all work against topical and systemic therapy reaching their target. This has driven a wave of newer sustained-release systems designed specifically to solve the adherence and frequency problem.

Traditional delivery routes

• Topical (drops/ointments) — most common, but poor bioavailability (much of the dose is lost to tear turnover and drainage); adherence is a genuine, underappreciated problem — studies show a large proportion of patients self-administer drops incorrectly, and non-adherence to glaucoma drops after surgery is common
• Subconjunctival/sub-Tenon injection — bypasses some corneal barrier limitations, useful for anterior segment and some periocular disease
• Intravitreal injection — the standard route for modern retinal therapeutics (anti-VEGF agents, corticosteroids) — direct, effective, but requires repeated injections, which itself became the impetus for sustained-release alternatives
• Systemic (oral/IV) — limited posterior segment penetration due to the blood-retinal barrier; reserved for specific indications (e.g., systemic antivirals, immunosuppressants for uveitis)

Current sustained-release systems (an active area)

• Intravitreal implants — biodegradable (e.g., dexamethasone implant for macular edema/uveitis) or non-biodegradable, releasing drug over months rather than requiring repeated injections
• Port Delivery System — a refillable, scleral-fixated intravitreal implant (FDA-approved 2021) providing continuous release of an anti-VEGF agent over months, refilled via periodic in-office exchange rather than monthly injections — a meaningful step toward reducing treatment burden for chronic retinal disease
• Intracanalicular inserts — small, biodegradable rods placed in the lacrimal punctum/canaliculus, releasing medication (e.g., a corticosteroid) over weeks — used for sustained anti-inflammatory delivery after ocular surgery without relying on patient drop compliance
• Sub-conjunctival/intracameral sustained-release implants — e.g., a bimatoprost intracameral implant for glaucoma, offering months of IOP-lowering effect from a single administration, aimed squarely at the adherence problem with daily glaucoma drops
• Drug-eluting contact lenses and punctal plugs — still largely in development, but an active research area for anterior segment sustained delivery

Why this matters

The shift toward sustained-release systems is driven by a well-documented adherence problem — a large proportion of glaucoma and post-surgical patients do not use topical drops as prescribed. Removing the dependence on daily patient action, even partially, is now a major direction for ophthalmic drug development, not just a niche innovation.