Ocular Pharmacology and Medication Administration
Routes and instillation
Topical drops are the mainstay. Wash hands, have the patient look up, pull the lower lid down to form a cul-de-sac, instill one drop without touching the tip to the eye or lashes, and apply punctal occlusion for 1 to 2 minutes. Wait 5 minutes between different drops. Shake suspensions. Ointments blur vision and are typically used at bedtime.
Drug classes and cautions
Anesthetics such as proparacaine 0.5% are for examination only and never dispensed for home use. Mydriatics: tropicamide 1% (short-acting), cyclopentolate 1%, atropine 1%, and phenylephrine 2.5% (avoid 10% in the elderly). Beta-blockers such as timolol are contraindicated in asthma and used cautiously with bradycardia or heart block. Alpha agonists such as brimonidine cause fatigue and are avoided in young children. Carbonic anhydrase inhibitors are sulfonamides. Prostaglandins cause iris darkening and eyelash growth.
Worked example
A patient with moderate persistent asthma is prescribed timolol 0.5% twice daily. Beta-2 blockade can precipitate bronchospasm, so the drug should be avoided; a prostaglandin analog or dorzolamide is preferable. Ask about wheeze and inhaler use before starting any beta-blocker.
Traps
Touching the dropper tip to the eye. Not asking about sulfa or preservative allergies. Failing to warn about stinging, blur, or systemic effects. Not documenting medication, concentration, and frequency.