Ocular Pharmacology and Pharmaceutical Agents
Core concepts
Know the major drug classes and their mechanisms: mydriatics and cycloplegics (tropicamide, cyclopentolate, atropine, phenylephrine), topical anesthetics (proparacaine, tetracaine), antibiotics and fluoroquinolones, corticosteroids and NSAIDs, anti-allergy agents (antihistamines, mast-cell stabilizers), and glaucoma medications (prostaglandin analogs, beta-blockers, alpha agonists, carbonic anhydrase inhibitors, rho kinase inhibitors). Understand onset, duration, and adverse effects, including systemic absorption through the nasolacrimal duct and the value of punctal occlusion.
Traps
Questions test duration differences: tropicamide is short-acting, cyclopentolate intermediate, atropine long-acting. Phenylephrine dilates without cycloplegia. Beta-blockers are contraindicated in asthma and heart block. Prostaglandin analogs cause iris darkening and eyelash growth. Remember that topical anesthetics are for procedures, not chronic use, because of corneal toxicity.
Worked rule of thumb
Before instilling a mydriatic, ask about angle-closure risk and asthma. Use the "duration ladder" for cycloplegics: tropicamide (hours), cyclopentolate (about a day), atropine (up to a week or more). Apply punctal occlusion for one to two minutes after instillation to reduce systemic absorption.