Table 1.

Comparison of various routes of ocular drug administration

Delivery routes	Advantages	Disadvantages	Diseases Treated
Topical	High patient compliance, self-administration, noninvasive nature	Corneal barrier, dilution and efflux, low bioavailability, high dosing	Conjunctivitis, keratitis, uveitis, episcleritis, scleritis, blepharitis
Subconjunctival and transscleral administration	Anterior and posterior drug delivery, ideal for depot formation	Choroidal and conjunctival circulation increase toxicity subconjunctival hemorrhage	Glaucoma, AMD cytomegalovirus retinitis,
Intracameral administration	Reduce corneal and systemic side effects. topical steroid use; high anterior chamber drug concentration	Toxic endothelial cell destruction syndrome and toxic anterior segment syndrome	Anesthesia, inflammation, endophthalmitis, pupil dilation
Intravitreal injection	Direct delivery to the vitreous humor and retina, BRB avoidance, high bioavailability and acute dosing	Poor patient compliance, invasiveness, drug toxicity, retinal detachment, cataract endophthalmitis, hemorrhage	AMD, central/branched retinal vein occlusion, diabetic macular edema, cytomegalovirus retinitis
Retrobulbar injection	Selective delivery to both anterior and posterior segments, avoidance of corneal and conjunctival barriers, long duration of action, a site for depot formulations	Poor patient compliance, invasiveness, drug deposition,compliances including pain, bleeding, infection, scarring, eyeball or optic nerve damage	Anesthesia
Systemic administration	High patient compliance	Blood ocular barriers, low bioavailability, systemic toxicity caused by high dosing	Scleritis, episcleritis, cytomegalovirus retinitis