Eye drops are the most commonly used medications in optometric practice. As a paraoptometric, you will handle, instill, and answer patient questions about ophthalmic drops every working day. From the diagnostic drops used during a comprehensive exam to the therapeutic drops prescribed for conditions like glaucoma, infections, and allergies, understanding the major categories of ophthalmic medications is essential knowledge for both your daily work and the CPO and CPOA certification exams.
This article provides an organized overview of the major ophthalmic drop categories. You do not need to memorize every brand name or precise pharmacokinetic detail for the paraoptometric exams, but you do need to understand the purpose of each category, why each type is used in specific clinical situations, and the general safety considerations that apply across all ophthalmic medications.
Think of this as your map of the territory. Subsequent articles in this series go deeper into individual categories such as mydriatics and cycloplegics, topical anesthetics, and allergy medications. Start here to build the framework, then explore the details.
Diagnostic Drops: Used During the Exam
Diagnostic drops are used in the office to help the doctor examine the eye or perform procedures. They are not prescribed for home use. As a paraoptometric, you will instill these drops frequently, often before the doctor even enters the room.
Mydriatics (Dilating Drops)
Mydriatics dilate the pupil so the doctor can examine the internal structures of the eye -- the lens, vitreous, retina, optic nerve, and blood vessels. Without dilation, the pupil is too small to allow a thorough view of the fundus. The most common mydriatic is phenylephrine 2.5%, a sympathomimetic that stimulates the dilator muscle of the iris. Tropicamide is also commonly used and provides both mydriasis and mild cycloplegia.
- Purpose: widen the pupil for fundus examination
- Common agents: phenylephrine, tropicamide
- Cap color: typically red or pink
Cycloplegics (Accommodation-Paralyzing Drops)
Cycloplegics temporarily paralyze the ciliary muscle, which prevents accommodation (the eye's ability to focus at near). This is essential for accurate refraction in children, who can accommodate strongly enough to mask their true refractive error -- especially hyperopia. Cycloplegics also produce mydriasis as a secondary effect. Cyclopentolate and atropine are the most commonly used cycloplegics.
- Purpose: relax accommodation for cycloplegic refraction
- Common agents: cyclopentolate, atropine, homatropine
- Also dilate the pupil (parasympatholytic mechanism)
Topical Anesthetics
Topical anesthetics temporarily numb the cornea and conjunctiva, allowing the doctor to perform procedures that would otherwise cause discomfort. They are used before Goldmann applanation tonometry, foreign body removal, gonioscopy, and certain other contact procedures. Proparacaine is the most commonly used agent because it produces the least stinging on instillation.
- Purpose: numb the eye for procedures
- Common agents: proparacaine, tetracaine
- NEVER prescribed for home use (causes corneal toxicity)
Fluorescein Dye
Fluorescein is a yellow-orange dye, not technically a drug, that is used to stain the tear film and corneal surface. Under cobalt blue light, fluorescein glows bright green. Areas where the corneal epithelium is missing (abrasions, ulcers, dry spots) take up the dye and appear as bright green patches. Fluorescein is also used to evaluate contact lens fit and to assess tear break-up time (TBUT) for dry eye. It is available as a drop or on strips that are moistened and touched to the conjunctiva.
- Purpose: visualize corneal defects and tear film quality
- Used with cobalt blue light on the slit lamp
- Often combined with benoxinate in tonometry strips
Therapeutic Drops: Prescribed for Treatment
Therapeutic drops are prescribed by the doctor for patients to use at home to treat eye conditions. As a paraoptometric, you need to understand what these drops do so you can answer basic patient questions, recognize drug names in the medical record, and understand why the doctor chose a particular medication. You will not prescribe these drops, but patients will ask you about them constantly.
Glaucoma Medications
The largest and most complex category of therapeutic drops. Multiple drug classes work by different mechanisms to lower intraocular pressure: prostaglandin analogs (latanoprost, travoprost) increase aqueous outflow, beta-blockers (timolol) decrease aqueous production, alpha-agonists (brimonidine) do both, carbonic anhydrase inhibitors (dorzolamide) decrease production, and Rho kinase inhibitors (netarsudil) increase trabecular outflow.
Cap color: often green (miotics/glaucoma), but varies by class
Anti-Infective Drops
Prescribed for bacterial, viral, or fungal eye infections. Antibiotics (fluoroquinolones like moxifloxacin, aminoglycosides like tobramycin, macrolides like erythromycin ointment) are the most common. Antivirals (trifluridine, ganciclovir gel) treat herpes simplex keratitis. Antifungals (natamycin) are used for fungal keratitis, which is uncommon but serious.
Prescribed based on the suspected or confirmed pathogen
Anti-Inflammatory Drops
Two main types: corticosteroids (prednisolone acetate, loteprednol, fluorometholone) are powerful anti-inflammatories used for uveitis and post-surgical inflammation, but carry risks of elevated IOP and cataract formation with prolonged use. NSAIDs (ketorolac, bromfenac, nepafenac) are less potent but do not carry the same steroid side effects and are commonly used after cataract surgery.
Cap color: tan or brown for steroids
Allergy Drops
Treat ocular allergy symptoms (itching, redness, tearing). Antihistamines block histamine receptors for fast relief. Mast cell stabilizers prevent the allergic response but must be used consistently. Combination drops (olopatadine/Pataday, ketotifen/Zaditor) provide both immediate and preventive action and are the most popular. Some are available over the counter.
OTC options make these commonly asked-about drops
Dry Eye Treatments
Range from simple artificial tears (over-the-counter lubricants that supplement the tear film) to prescription immunomodulators. Cyclosporine (Restasis, Cequa) and lifitegrast (Xiidra) reduce inflammation on the ocular surface and increase tear production over time. Artificial tears come in preserved (multi-use bottles) and preservative-free (single-use vials) formulations.
Patients often ask which artificial tears are best
Other Therapeutic Drops
Additional categories include hyperosmotic drops (sodium chloride 5% for corneal edema), decongestants (naphazoline -- used sparingly due to rebound redness), and newer specialty drops like low-dose atropine for myopia control in children. The field continues to evolve with new agents entering the market regularly.
Decongestants should not be used long-term
Cap Color Conventions
The ophthalmic industry developed cap color coding to help distinguish drug categories at a glance. While these conventions are widely followed, they are not legally mandated, and some manufacturers use different colors. Never rely on cap color alone to identify a drop -- always read the label. That said, knowing the general conventions is useful in practice and is tested on certification exams.
Red / Pink
Mydriatics (dilating drops) such as phenylephrine, tropicamide, cyclopentolate
Green
Miotics and glaucoma drops such as pilocarpine, timolol
Tan / Brown
Corticosteroid drops such as prednisolone acetate
White
Multiple categories; not specific to one drug class
Yellow
Beta-blockers (some manufacturers)
Turquoise / Teal
Prostaglandin analogs (some manufacturers)
Exam Tip
The CPO and CPOA exams may test cap color conventions, but they also test whether you know that cap color alone is not a reliable identification method. The correct answer is always to read the drug name and concentration on the label. Cap color is a helpful quick reference, not a substitute for proper identification.
Practice pharmacology questions for your exam
Opterio covers ophthalmic drops, drug classes, and clinical procedures with AI-powered explanations for every answer.
The Paraoptometric's Role with Ophthalmic Drops
As a paraoptometric, you occupy a critical position in the ophthalmic drop workflow. You are the person who prepares drops, instills them, documents their use, and often fields patient questions. Here is what you need to know about your specific responsibilities.
Preparation and Verification
Before instilling any drop, verify the correct drug, concentration, and target eye against the doctor's order. Check the expiration date on the bottle. Look at the solution -- it should be clear (unless it is a suspension like prednisolone that requires shaking). If the bottle has been contaminated (tip touched a surface), it should be replaced.
Allergy Check
Always verify the patient's allergy status before instilling any drop. Check the medical record and ask the patient directly. Pay special attention to sulfa allergies (relevant for some glaucoma drops), preservative sensitivities (especially benzalkonium chloride), and any history of adverse reactions to dilation drops.
Knowing Onset Times and Durations
You need to know approximately how long it takes for each diagnostic drop to reach full effect so you can time things properly. Tropicamide takes about 20-30 minutes for full dilation. Cyclopentolate needs 30-60 minutes for full cycloplegia. Proparacaine works within 15-20 seconds but lasts only 15-20 minutes. Timing dilation appropriately keeps the clinic running smoothly.
Documentation
Document every drop instilled: the drug name, concentration, which eye (OD, OS, or OU), the time, and who instilled it. Documentation protects the patient (the doctor needs to know what was given and when) and protects you (it proves proper procedure was followed). Many practices use templates or drop logs for this purpose.
Patient Education
Patients will ask you about their prescribed drops -- what they are for, how to use them, and what side effects to expect. You should be prepared to explain the general purpose (for example, that glaucoma drops lower eye pressure to protect the optic nerve) without overstepping into medical advice. Always direct specific medication questions to the doctor.
General Safety Principles
Sterility
The tip of an eye drop bottle must never touch the eye, eyelashes, fingers, or any other surface. Contact with these surfaces introduces bacteria into the bottle and can lead to contamination and potential infection. Hold the bottle 1-2 cm above the eye when instilling drops. If the tip touches anything, notify the doctor -- the bottle may need to be discarded.
Expiration Dates
Check expiration dates regularly. Expired drops may lose efficacy or, worse, the preservative system may break down, allowing microbial growth. Most multi-dose drop bottles also have an in-use expiry (typically 28 days after opening for prescribed drops) separate from the printed expiration date. Office drops should be checked at the start of each day.
Narrow Angle Screening
Before instilling any mydriatic or cycloplegic drop, the patient's risk for angle-closure glaucoma must be assessed. Dilation in a patient with narrow angles can precipitate acute angle closure -- a medical emergency. Many offices screen for this using the van Herick technique on slit lamp or by reviewing the patient's history. Always follow your office protocol for pre-dilation assessment.