Pharmacology in Ophthalmology

Pharmacology in Ophthalmology

• Table of Contents: Includes topics like anatomy of the eye, treatment options, pharmacokinetics, eye lubricants, medications for eye exams, glaucoma management, ocular therapies, and immunomodulators.

Anatomy of the Eye

• Structures: The slides feature diagrams illustrating the internal structures of the eye, including the conjunctiva, palpebra, ciliary body, anterior/posterior chambers, cornea, lens, vitreous chamber, retina, optic nerve, optic disc, choroid, and sclera.

• Blood-ocular Barriers: Explains how the blood-ocular barriers complicate drug penetration. Shows separate diagrams of the corneal barrier, blood aqueous barrier, vitreal barrier, tear film barrier, and blood retinal barrier.

Treatment Options

• Local Application: Solutions, suspensions, lipids, and oil emulsions are used for frequent application to the cornea. Conjunctival implants or therapeutic contact lenses can offer prolonged release.

• Injections: Subconjunctival depot injections allow for slow, continuous absorption; intracameral injections (anterior or posterior) target the aqueous or vitreous humor, and retrobulbar injections target the retrobulbar space. Intravitreal or suprachoroidal implants are also possible.

• Other Considerations: Eye washes with 0.9% NaCl saline solution aid in removing eye discharge. Gel formulas are often better for surgery to prevent dry eye, with medication like pilocarpine directly stimulating the lacrimal gland.

Topic Ocular Treatment Specifications

• Restraint: Physical restraint is always necessary during application.

• Administration Frequency: Frequent administration is often needed (more so for eye drops than eye ointments).

• Local Action: The advantage is high local drug concentration and rapid action, but ocular toxicity poses a risk. Conjunctiva, sclera, cornea, and the anterior chamber commonly benefit.

Pharmacokinetics

• Blood-ocular Barriers: These are complex, protective mechanisms that complicate the delivery of drugs to the interior of the eye; the resistance to the absorption and corneal penetration is reduced or eliminated in cases where the corneal or conjunctival epithelium is compromised .

• Eye Complexity: The eye is complex with a specialized vascular system for nourishment, maintaining intraocular pressure, and nourishing the receptors.

Eye Drops vs. Eye Ointments

• Solutions and Suspensions: Diagrams show examples of eye drops (Cefenicol® CA 5 mg/ml, chloramphenicol etc) and ointments (Ophthalon®, chloramphenicol etc)

Lubricants and Moisturizers

• Eye Wash: Uses neutral saline solution (0.9% NaCl) to clear particles and discharge.

• Dry Eye Treatment: Veterinary formulas are better than human products, to treat dry eye and keratoconjunctivitis because of the lack of the disease in humans. For surgery gel formulas are better.

Glaucoma

• Aqueous Humor Production and Drainage: The anatomy and flow of aqueous humor (diagram featured) and the implications for glaucoma (diagram featured) are presented.

• Therapeutic Options: Options for decreasing eye pressure include reducing aqueous humor production and increasing drainage.

Parasympathomimetic Drugs (Miotics)

• Direct-acting: Pilocarpine and Carbachol are examples used for pupil constriction and increasing drainage, decreasing intraocular pressure and for treating glaucoma.

• Indirect-acting: Demecarium Bromide, Ecothiophate, and Physostigmine directly affect the receptors and cause myosis by affecting cholinergic receptors.

Prostaglandin Analogs

• Increased Outflow: In intraocular pressure, these drugs increase uveoscleral aqueous humor outflow.

• Mechanism Unknown: Results in rapid intraocular pressure reduction, but the precise mechanism remains unclear.

Reducing Aqueous Humor Production

• Carbonic Anhydrase Inhibitors: They inhibit the production of aqueous humor. These are used in humans to treat open-angle glaucoma or secondary glaucoma and used adjuvants to beta-adrenergic drugs or as a sole therapy.

Sympatholytic Drugs

• Selective α-antagonists: Used for regulating post-operative intraocular pressure, but seldom used due to unwanted side effects.

• Selective β-antagonists: Useful in combination with other drugs for treating glaucoma; timolol, levobunolol, carteolol, metipranolol, and betaxolol are examples.

Ocular Anti-inflammatories

• NSAIDs/NSAID-like compounds: NSAIDs are used for reducing inflammation and providing pain relief - specifically for allergic conditions like conjunctivitis.

• Corticosteroids: Used for reducing inflammation, but carries significant side effects and should not be used with abrasions, ulcers or corneal herpes infections.

Ocular Antibiotics and Antivirals

• Anti-inflammatories: Effective to various corneal conditions and used for surgery and infections. Antibiotics and antivirals (Acyclovir, Valacyclovir, Famciclovir, Trifluridine, or Idoxuridine) target various fungal or herpes infections.

Antifungal Drugs

• Types for infections: Natamycin, Povidone-iodine, Amphotericin B, Itraconazole, and Miconazole are examples.

Immunomodulators

• Cyclosporine: Used for treating immune-mediated eye diseases like keratoconjunctivitis sicca. Intraocular implants are available which provide long-lasting treatment.

This quiz covers essential pharmacology concepts as they relate to ophthalmology. Topics include anatomy of the eye, treatment options, pharmacokinetics, and various ocular therapies. Test your knowledge on medications for eye exams and glaucoma management.