In understanding how much of an artificial tear or a prescription eye drop actually reaches its target tissue, it is helpful to appreciate the significant obstacles to drug penetration that the eye presents.
The average size of a topical drop is 50 µL and is dropped into a 30 µL “reservoir,” ie, the ocular surface. There is some spillage and nasolacrimal drainage. Tearing and blinking cause dilution and increase the spillage and nasolacrimal clearance.
The volume of the tear film is 7 µL to 10 µL; it turns over at (Read more...)