This review examines drug delivery across the blood-retinal barrier (BRB) for posterior-segment diseases, proposing a shift from a barrier-centric to a 'biological gateway' framework that integrates inner/outer BRB transport mechanisms, route-specific delivery strategies, and emerging drug delivery platforms.
The authors synthesize evidence across delivery routes (systemic, intravitreal, suprachoroidal, subretinal) and platforms—including sustained-release implants, port-based systems, gene therapies, hydrogels, polymeric/lipid carriers, biomimetic systems, inorganic nanomaterials, and stimulus-responsive platforms—showing how material properties, pharmacokinetics, and BRB biology collectively determine drug localization and efficacy.
As a narrative review, it does not perform a systematic literature search or meta-analysis, limiting the strength of any comparative conclusions. No original clinical or experimental data are presented, so findings depend entirely on the quality of cited primary sources.
Clinicians designing or selecting posterior-segment therapies should consider BRB transport mechanisms (not just barrier restriction) alongside delivery route and formulation properties to optimize drug exposure and durability. Emerging platforms such as suprachoroidal delivery, refillable port implants, and stimulus-responsive carriers offer new options for sustained retinal drug levels beyond repeated intravitreal injections.
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