7.1 Topical ophthalmic medications & drug classes

Topical Ophthalmic Medications and Drug Classes

Topical medications are the backbone of eye care, and the certified ophthalmic technician must understand what each drug class does, why it is prescribed, and how it is instilled. Most ophthalmic drugs are delivered as drops or ointments applied directly to the ocular surface, where the tear film and cornea act as gatekeepers for absorption. A working knowledge of drug classes lets the technician anticipate physician orders, reinforce patient education, and recognize dangerous interactions.

Glaucoma medications

Glaucoma therapy lowers intraocular pressure (IOP) either by decreasing aqueous production or by increasing aqueous outflow.

• Prostaglandin analogs (latanoprost, bimatoprost, travoprost) increase uveoscleral outflow. They are first-line, dosed once nightly, and carry teal/turquoise caps. Side effects include iris and periocular hyperpigmentation and eyelash growth.
• Beta-blockers (timolol, betaxolol) reduce aqueous production; caps are yellow or blue. Because they are absorbed systemically, they can cause bradycardia and bronchospasm, so always ask about asthma, COPD, and heart block.
• Alpha-2 agonists (brimonidine, apraclonidine) both reduce production and increase outflow; caps are purple.
• Carbonic anhydrase inhibitors (CAIs) (dorzolamide, brinzolamide) decrease production; caps are orange. Oral acetazolamide is the systemic form.
• Cholinergic (miotic) agents (pilocarpine) increase trabecular outflow and constrict the pupil; caps are dark green.

Diagnostic and surgical agents

• Mydriatics and cycloplegics dilate the pupil (and, for cycloplegics, relax accommodation) so the physician can examine the fundus. Phenylephrine, tropicamide, cyclopentolate, and atropine all carry red caps.
• Topical anesthetics (proparacaine, tetracaine) numb the cornea for tonometry, foreign-body removal, and gonioscopy. Onset is 15-20 seconds and duration 10-20 minutes. They are never dispensed for home use because repeated dosing is toxic to the corneal epithelium.
• Vital dyes, chiefly sodium fluorescein, stain areas of epithelial defect and are essential for applanation tonometry and Seidel testing. Fluorescein fluoresces green under cobalt-blue light and can permanently stain soft contact lenses, so lenses are removed first.

Therapeutic drops

• Antibiotics (fluoroquinolones, aminoglycosides, polymyxin combinations) treat bacterial conjunctivitis and keratitis and provide surgical prophylaxis; caps are tan/brown.
• Corticosteroids (prednisolone, dexamethasone, loteprednol) suppress inflammation after surgery or uveitis; caps are pink. Steroids raise IOP in responders and can worsen herpetic or fungal infection, so they demand physician oversight.
• NSAIDs (ketorolac, nepafenac, bromfenac) control pain and cystoid macular edema without the IOP risk of steroids.
• Artificial tears and lubricants relieve dry eye; preservative-free formulations are preferred for frequent dosing.

Quick-reference: class, action, example, cap color

Instillation technique and systemic absorption

Correct technique maximizes the dose reaching the eye and minimizes side effects:

1. Verify the correct patient, drug, eye (right, left, or both), and concentration.
2. Wash hands and avoid touching the dropper tip to the eye or lashes.
3. Have the patient tilt the head back and look up; gently pull down the lower lid to form a pocket in the inferior fornix.
4. Instill a single drop. The conjunctival sac holds only about 7-10 microliters, far less than one drop, so extra drops are wasted and increase systemic exposure.
5. Have the patient close the eyes gently for one to two minutes.
6. Apply punctal occlusion, light pressure over the lacrimal sac at the inner canthus, to block nasolacrimal drainage. This keeps the drug on the eye and reduces absorption through the vascular nasal mucosa, the main route of systemic side effects such as timolol-induced bradycardia.

When multiple drops are ordered, wait at least five minutes between different medications so the first is not washed out, and instill drops before ointments. Teach patients that brief stinging is normal and that suspensions like brinzolamide must be shaken before use for an accurate dose.

Drops, ointments, and combination products

Ointments and gels last longer on the eye and are useful at bedtime or for young children who blink drops away, but they blur vision, so they are usually reserved for nighttime dosing. When both a drop and an ointment are ordered, the drop goes first because an ointment would form a barrier that blocks absorption of a later drop. Combination products simplify regimens and improve adherence: fixed-combination glaucoma drops (for example, a beta-blocker paired with a CAI or an alpha-agonist) deliver two IOP-lowering mechanisms in one bottle, and antibiotic-steroid drops treat infection and inflammation together after certain procedures.

Storage, preservatives, and safety checks

Several practical points protect patients. Most drops contain the preservative benzalkonium chloride, which can irritate the ocular surface with frequent use, so preservative-free single-use vials are preferred for patients dosing more than four to six times daily. Some drops, such as certain prostaglandins, require refrigeration until opened. Always check the expiration date and discard opened multidose bottles per the label, typically within 28 days. Finally, confirm that the patient is not allergic to a class before instillation, and never assume the strength: a 10% phenylephrine label differs dramatically in risk from 2.5%, and reading the concentration aloud is a simple safeguard against a serious dosing error.