Pharmacological action of eye @nursesoutlook

Pharmacological action of the eye

The penetration of the eye by drugs is restricted by two barriers, the epithelial membrane of the corner and the blood-aqueous humour barrier.the latter is formed by the endothelial of the vessels and the epithelium of the ciliary body.this ciliary barrier has some characteristics in common  with the blood Bra barrier,which is characterised by its right structure.

Drugs for treatment of eyes are usually  administered in three forms

1.topically on the surface of eye

2.by local injection

3.by systemic application

Among the 3 priority  is emphazised  for local application

Local application

Eye drops are usually administered into the conjunctival sac which has capacity of only .01ml.the volume of an eye drop is 0.05ml and therefore usually  4/5 of the volume leaks out immediately  after each closure of eyelid.

The installed drug will be diluted by the tear  fluid and the concentration is usually halved after 1/2 minute due to drainage through the nasolacrimal duct.
The systemic effects  of eye drops  may also occur after absorption from the nasal mucosa. By altering the composition of the diluents the contact time and hence also local absorption can be extended 4-7 times.