METHODS OF LOCAL APPLICATION OF DRUGS
a. Application to corneal surface
b. Sub-conjunctival route
c. Retrobulbar route
d. Direct injection into the aqueous or vitreous
A. Application to corneal surface
The drug through this route must fulfil the necessary criteria for passing the corneal barrier to penetrate into the eye.
Formally, the drug delivery kinetics, passing through this route, can be devided in two parts.
(b) Subconjunctival Route
This route including injection under the bulbar conjunctiva used to achieve high concentrations of drug in the anterior chamber. Antibiotics, steroids, mydriatics can be given by this route.
Subconjunctival injections are painful, so this route is used only in severe cases of ocular inflammation or infection of the anterior segment.
(C) Retrobulbar Route
Drugs can be delivered to the back of the orbit by retro-bulbar injections.
This is the route for local anaesthesia in Ocular Surgery.
Steroids may also be injected by this route to reduce optic nerve or posterior segment inflammation.
(D) INTRACAMERAL ADMINISTRATION
Intracameral administration involves placing drug directly into the anterior chamber of the eye. This is most commonly associated with cataract extraction, IOL implantation and Phacoemulsification during which a viscoelastic substance is injected into the anterior chamber to protect the corneal endothelium. Antibiotics are not routinely injected into the anterior chamber as there is significant risk of complications as well as drug toxicity.
(E) INTRAVITREAL ADMINISTRATION
The intravitreal injection is primarily reserved as a last effort to save eye with severe acute infection or intraocular inflammation.
Intravitreal antibiotics is the treatment of choice for endophthalmitis. Intravitreal liquid silicone is used for the treatment of complicated Retinal Detachment.
Recently intravitreal ganciclovir has been used with success in treating cytomegaloretinitis in patient with AIDS.
OPTOMETRY-SHARP VISION
Optometrist