Principles of therapeutics.

This research article discusses the different methods of administering therapeutic drugs for diseases of the anterior segment (front part) of the eye, including topical application, the use of drug-delivery devices, subconjunctival and retrobulbar injections, as well as systemic administration, and the scenarios where these methods are best utilized.

Topical Administration and Drug-Delivery Devices

• For treating diseases of the anterior (front) segment of the eye, the preferred method of drug administration is usually the topical application of medication. However, this method typically results in short-lived drug levels, which means that repeated, frequent therapy or continuous perfusion (the flow of a drug solution into an organ or a tissue) is often necessary to maintain therapeutic drug concentrations.
• If frequent treatment is not feasible, the article suggests that topical therapy could be supplemented with a drug-delivery device such as a collagen shield or a contact lens. These devices can help to maintain the necessary drug levels over a longer duration.

Subconjunctival and Retrobulbar Injections

• Subconjunctival injections – which involve delivering medication under the thin membrane (conjunctiva) covering the front of the eye – can also be used to furnish an effective level of drug treatment. These injections are particularly recommended for medications that have low solubility and thus exhibit poor penetration of the cornea (the clear, outer layer at the front of the eye).
• Retrobulbar injections – which see drugs administered to the back of the eye, behind the eyeball – are rarely prescribed. They are primarily used for regional anesthesia to numb the area for certain eye procedures.

System Approach and Intraocular Injections

• Drugs can also be administered systemically – for example, orally or by injection – when there’s a need for anti-inflammatory therapy. Nevertheless, it may be challenging to achieve the needed therapeutic levels of antibiotic agents specifically in the eye due to the present blood-eye barrier which prevents certain substances from entering the eye.
• In severe instances where a high level of a drug is required inside the eye, intraocular injection might be necessary. This method involves an injection directly into the eye and can help bypass the blood-eye barrier in order to achieve higher concentrations of the therapeutic drug within the eye.