The 3 primary methods of administering medications to the eye are topical, local ocular (such as under the conjunctival tissue or into the vitreous portion of the eye), and systemic (given by mouth or injection). The most appropriate method of administration depends on the area of the eye to be medicated.
Drugs Used to Treat Glaucoma
Topical medications, such as gels or solutions containing prostaglandins, miotics (drugs that cause the pupil to contract), beta-blocking adrenergics, and topical carbonic anhydrase inhibitors (a type of diuretic), are the primary drugs for treatment of glaucoma, but these are often supplemented with drugs taken by mouth or injection.
Osmotic diuretics are used for the emergency treatment of sudden and severe glaucoma. Osmotic diuretics are used to reduce the pressure in the eye by reducing fluid buildup. Oral carbonic anhydrase inhibitors are also used in the treatment and management of short-term glaucoma. They reduce the amount of fluid within the eye.
Drugs Used to Treat Infectious Disease
Treatment of infectious diseases that affect the eyes will depend on the organism that causes the disease. Viral diseases (such as feline herpesvirus keratitis and conjunctivitis) can usually be treated with topical antiviral drugs. If topical treatment does not work, oral or injectable antiviral drugs may be required.
Antibacterial drugs may be given topically, orally, or by injection for most bacterial or protozoal infections. If inflammation is severe, topical corticosteroids or other anti-inflammatory drugs given by mouth or by injection may be helpful in reducing pain and inflammation.
Dogs and cats diagnosed with fungal infections affecting the eye require systemic treatment—that is, treatment with a drug that is distributed to all parts of the body. Along with systemic antifungal drugs, topical and systemic anti-inflammatory drugs and topical mydriatics and cycloplegics are needed to control pain in the eye.
Drugs Used to Treat Wounds or Trauma
All penetrating wounds of the eye should be considered infected and treated with systemic, broad-spectrum bactericidal antibiotics. Antibiotic treatment lasts for at least 14 to 21 days.
Penetrating eye trauma causes severe inflammation, so it is also treated with nonsteroidal anti-inflammatory drugs. These drugs are given intravenously or by mouth. Because treatment of eye injuries with these drugs may cause adverse effects on the digestive system, veterinarians often prescribe additional drugs to limit these effects, such as H2-blockers or proton pump inhibitors.
Drugs Used to Treat Inflammation
Many infectious and noninfectious diseases cause inflammation within the eye (such as inflammation of the optic nerve or uvea). Irreversible damage and blindness may result if not caught early. Both topical and systemic corticosteroids and nonsteroidal anti-inflammatory drugs are used to control inflammation, depending on the cause.