Pharmacology

Pharmacology is 6% of the exam: diagnostic and therapeutic medications, how they are instilled, and their side effects. The assistant puts in diagnostic drops, records every drug the patient uses, teaches drop technique, and notices side effects early. Choosing and prescribing a drug is the physician's job.

Name stems are fast clues — -olol (beta blockers, such as timolol), -prost (prostaglandin analogs, such as latanoprost), -caine (anesthetics, such as proparacaine), -floxacin (fluoroquinolone antibiotics). Learn each drug by its generic name.

Cap colors — a standard color code marks the caps of many eye drops: red for mydriatics and cycloplegics, yellow or blue for beta blockers, teal for prostaglandin analogs. Color is only a cross-check; the label is read every time.

Forms — solutions are clear; suspensions look cloudy and are shaken before each drop, or the amount of drug varies. Gels and ointments stay on the eye longer but blur vision, so ointment is often used at bedtime.

Routes — most eye drugs are topical. Some are taken by mouth (acetazolamide), given into a vein (fluorescein for angiography, mannitol in an angle-closure attack), or injected into the eye by the physician (intravitreal injections; see the Surgical Assisting guide).

Mydriatics and cycloplegics (red caps) — a mydriatic dilates the pupil; a cycloplegic also paralyzes accommodation, the eye's focusing. A miotic, such as pilocarpine, does the opposite and constricts the pupil.

Standard adult dilation pairs tropicamide + phenylephrine — sphincter blocked and dilator stimulated at once, so the pupil opens wider and faster than with either drop alone. When atropine is ordered for a small child, the lowest effective strength, punctal occlusion, and teaching parents the warning signs are standard. The Refractometry guide covers the cycloplegic refraction itself.

Topical anesthetics — proparacaine and tetracaine: onset in seconds, duration 10–20 minutes, long enough for tonometry, gonioscopy, and minor procedures. Never dispensed to patients — repeated use melts corneas, and the numbness hides the damage as it happens. For tonometry, anesthetic goes in before or with the fluorescein; the Tonometry guide covers the no-rubbing warning.

Stains — fluorescein highlights epithelial defects (green under cobalt blue) and draws the applanation mires; IV fluorescein runs angiography, whose expected effects and reactions are in the Ophthalmic Imaging guide. Soft contact lenses come out first and stay out until the dye has cleared, because fluorescein stains them. Lissamine green and rose bengal stain devitalized cells — the dry-eye workup dyes. Rose bengal stings; lissamine green is gentler.

Check every time — the right patient (confirm identity, such as name and date of birth), the right drug and strength (read the label, then the expiration date), the right eye, and the right time. Diagnostic drops go in only on the physician's order or the office protocol.

Allergies first — confirm allergies before any drop, every visit, and record the reaction along with the drug. A past reaction to a drop, a preservative, or a drug class (such as sulfa before a carbonic anhydrase inhibitor) reaches the physician before the drop does.

Record it — the drug and strength, which eye, the time, and your initials. A drop in the wrong eye or the wrong patient goes to the physician at once and is documented per office policy, because some drops are risky in certain eyes: a dilating drop can close a narrow angle.

Tests come first — acuity, pupils, keratometry, and optical biometry are measured before any drop or dye, and any manifest refraction or visual field ordered that day comes before dilation.

Screen before dilating — dilating an eye with a narrow drainage angle can set off acute angle closure. Always screen for shallow anterior chambers per protocol and document pupil status before dilating; the Pupil Assessment guide covers the pupil exam. In the penlight screen, light from the temple side is aimed across the eye, parallel to the iris: a deep chamber lets it light the whole iris, while in a shallow one the iris bows forward and a shadow falls across its nasal side. It is only a rough screen; a deep-looking chamber does not rule out a narrow angle. A shallow-looking chamber, a past angle-closure attack, or a chart note warning against dilation goes to the physician, who decides who is dilated and with what.

Warning signs — eye pain, redness, halos around lights, headache, nausea, or vomiting in the hours after dilation can mean angle closure. Near blur alone is expected; blur with pain or halos is not. The patient calls at once, or goes to an emergency department if the office is closed, and the physician hears about it now.

Dilation counseling — near blur and light sensitivity for roughly 4–6 hours after routine dilation, longer after cyclopentolate or atropine. Sunglasses help, driving may be difficult, and a driver should be arranged when possible.

The same steps serve the clinic and the patient's home; the Ophthalmic Patient Services and Education guide covers teaching them.

Teach punctal occlusion to limit systemic absorption (especially beta blockers, and atropine in children).

Bottle discipline — the tip is sterile until it touches anything; date bottles per policy; discard expired or contaminated stock. Contaminated diagnostic bottles have caused clinic outbreaks. Recap at once, never top off an old bottle from a new one, and never wipe a tip with a finger. Store each drug as its label directs (some need refrigeration), and discard a clear solution that turns cloudy or changes color, whatever its date. The Microbiology guide covers fluorescein and shared-drop risks.

The assistant recognizes classes, mechanisms, and red-flag interactions; the physician prescribes. Each class lowers pressure by slowing aqueous production, helping aqueous drain out, or both (the General Medical Knowledge guide traces the drainage routes).

Emergencies — in acute angle closure the physician may add oral/IV acetazolamide and hyperosmotics (mannitol) to crash the pressure while definitive care is arranged.

At the workup — record when each glaucoma drop was last used (the Tonometry guide explains why), and note a miotic such as pilocarpine before pupils and fields are tested, because a small pupil changes both.

Antibiotics — erythromycin ointment for lid disease, minor surface infections, and prophylaxis, including newborns; fluoroquinolone drops for serious bacterial keratitis. Recognize, don't prescribe. Antibiotics do not treat viruses or fungi: herpes simplex needs an antiviral, and fungal keratitis an antifungal.

Steroid drops — powerful and double-edged: IOP spikes in steroid responders, posterior subcapsular cataract with time, and fuel for herpetic and fungal infection. Physician-managed with monitoring; refill requests get routed, never rubber-stamped. Many are suspensions, so shake before each drop.

NSAID drops — ketorolac and similar drugs ease pain and inflammation, often around cataract surgery, without a steroid's pressure and cataract risks. Long use on a damaged cornea can slow healing and, rarely, let it break down, so a surface that is not healing goes to the physician.

Allergy drops — itching is the hallmark symptom; dual-action antihistamine/mast-cell stabilizers (olopatadine) treat now and prevent later. Rubbing the eyes makes allergy worse.

Artificial tears — drops, gels, and ointments; frequent dosers and severe dry eye do better preservative-free; benzalkonium chloride (BAK) irritates with heavy use.

Reactions — red, itchy, swollen lids after a new drop can be an allergy to the drug or its preservative; tell the physician. After any drug or dye, hives, facial swelling, wheezing, or lightheadedness can mean anaphylaxis: activate the emergency protocol (see the General Medical Knowledge guide).

The systemic connection runs both ways — drops drain through the nasolacrimal duct into the bloodstream (hence punctal occlusion), and systemic drugs mark the eye: hydroxychloroquine (retinal screening), tamsulosin (floppy iris at surgery), anticoagulants (bleeding risk), steroids by any route (cataract, pressure rise).

Be ready to name each diagnostic drop's job, recall that dilating drops wear red caps, explain the tropicamide-phenylephrine pairing, pick the drop for a child's cycloplegic refraction, list the checks before any drop, screen for a shallow chamber, name the angle-closure warning signs, describe drop and ointment technique, decode the name stems, match glaucoma classes to their mechanisms and side effects, recognize the risks of steroids, anesthetics, phenylephrine, beta blockers, and atropine in children, and keep a bottle safe.