Comparison of various routes of ocular drug administration: benefits and obstacles (Gaudana et al., 2010)
| Route | Benefits | Obstacles | Diseases/Disorders Treated |
|---|---|---|---|
| Topical | Patient compliance is high; self-administration and noninvasive nature | Corneal barrier difficult to penetrate; dilution and efflux via tears is high | Conjunctivitis, keratitis, uveitis, episcleritis, scleritis, blepharitis |
| Intravitreal | Direct delivery to retinal and vitreal structures; drug has high bioavailability | Patient compliance low; risk of retinal detachment, hemorrhage, development of endophthalmitis or cataracts | AMD, BRVO, CRVO, DME, CMV retinitis |
| Sub-Tenton | Relatively noninvasive, decreased risk of comorbidity compared with intravitreal delivery, maintains high vitreal drug levels | Retinal pigment epithelium is a barrier; subconjunctival hemorrhage, chemosis | DME, AMD, RVO, uveitis |
| Posterior juxtascleral | Advantageous for drug depository; avoids intraocular damage, and macula can sustain drug level for 6 mo | Retinal pigment epithelium barrier, and surgical procedure required; | AMD, risk of endophthalmitis |
| Systemic/oral | Promotes patient compliance, noninvasive mode of delivery | Retinal and blood-aqueous barriers; low bioavailability leading to systemic toxicity | Scleritis, episcleritis, CMV retinitis, posterior uveitis |
| Intracameral | Reduces systemic and corneal side effects vs. topical steroid use; high anterior chamber drug concentration | Toxic endothelial cell destruction syndrome and toxic anterior segment syndrome pose major risks to patients | Anesthesia, prevention of endophthalmitis, inflammation, pupil dilation |
| Subconjunctival | Anterior and posterior delivery method, ideal for depot formation | Choroidal and conjunctival circulation of therapies increases toxicity | Glaucoma, CMV retinitis, AMD |
| Retrobulbar | Minimal IOP involvement, ideal for high local anesthetic administration | Respiratory arrest, retrobulbar hemorrhage, globe perforation | Anesthesia |
BRVO, branched retinal vein occlusion; CMV retinitis, cytomegalovirus retinitis; CRVO, central retinal vein occlusion; IOP, intraocular pressure.