Noncomeal ocular absorption

In a study by Schoenwald et al., the conjunctival/scleral pathway yielded higher iris-ciliary body concentrations for all compounds evaluated with the exception of lipophilic rhodamine B (33). Romanelli et al. demonstrated the absorption of topical ocular bendazac into the retina-choroid via the conjunctival-scleral pathway (34). Noncomeal absorption was influenced more by physicochemical properties of the drag than characteristics of the formulation, whereas conversely transcomeal absorption could be influenced more by characteristics of the formulation. 

Routes of absorption that lead to the removal of drag from the precorneal area, and do not result in direct ocular uptake, are referred to as nonproductive. These noncomeal pathways, which are in parallel with comeal absorption and include conjunctival uptake and drainage via the nasolacrimal duct, lead to systemic absorption by way of conjunctival blood vessels in the former case and removal through the nasal mucosa and gastrointestinal tract in the latter. As discussed, drag can penetrate the conjunctiva, and, via the sclera, enter the eye however, blood vessels within the conjunctiva can also lead to systemic absorption. 

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