Administration of drugs to eye

• Both local and systemic routes are available. Local routes include topical, subconjunctival and intravitreal.
• Choice of route of administration depends on location of disease (eg eyelids, ocular surface, anterior segment, posterior segment), pharmacology of drug (eg ability to penetrate cornea and blood-ocular barriers), potential for systemic side-effects and availability of drug preparations.
• Subconjunctival administration is reserved when topical application is not possible or the disease is not responding to topical therapy. Following topical anesthesia the drug is injected under the bulbar conjunctiva.
• Intravitreal injections are rarely performed.
• Systemic therapy is needed to reach therapeutic drug levels in the eyelids and posterior segment.

Topical drug preparations

• Drop and ointment forms exist and should be applied directly to the surface of the eye, eg lower conjunctival sac or cornea.
• Drops are easier to apply but have decreased ocular surface contact times nesessitating more frequent application.
• Ointments have prolonged corneal contact time, require less frequent application, have lubricating properties but can cause blurring of vision.
• Corneal penetration and intraocular delivery of topical drugs is variable. To penetrate the corneal epithelium and stroma the drug should have both lipophilic and hydrophilic properties.
• Most topical drug formulations contain preservatives such as benzaalkonium chloride. These can be irritating and epitheliotoxic.
• If more than one drug is to be applied, separate administration by >5 min.
• Topically applied drugs can have systemic effects, eg atropine Atropine , phenylephrine Phenylephrine and corticosteroids.

Anti-infective eye preparations

Anti-inflammatories

Mydriatics and cycloplegics

Antiglaucoma medications

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.

Other sources of information

• Ramsey I (2008) BSAVA Small Animal Formulary. 6th edn. British Small Animal Veterinary Association. ISBN 978 1 905319 11 4.
• British National Formulary (2008) 55th edn. BMJ Group and RPS Publishing.
• Petersen-Jones S & Crispin S (2002) BSAVA Manual of Small Animal Ophthalmology. 2nd edn. British Small Animal Veterinary Association. ISBN 0 905214 54 4.