Diagnostic Drugs for Optometrists: Mydriatics, Cycloplegics, Anaesthetics and Stains
Last updated: November 2026
RPC Rounds for Optometrists · B.Optom study guide
Optometrists use a small set of diagnostic drugs every day: drops to dilate the pupil, to paralyse accommodation, to numb the cornea and to stain the surface. Each is safe when used correctly, but each has contraindications and rare serious effects you must recognise.
Mydriatics (dilate the pupil)
| Drug | Action | Use and timing | Cautions |
|---|---|---|---|
| Tropicamide 0.5–1% | Antimuscarinic (blocks the sphincter); weak cycloplegic | Routine dilation; maximum at about 20–30 minutes; lasts about 4–6 hours | Rarely triggers angle closure in narrow angles |
| Phenylephrine 2.5% (10% rarely) | Alpha-agonist (stimulates the dilator) | Added to tropicamide for better dilation, especially dark irides | Avoid 10% in heart disease, hypertension, infants; can raise blood pressure |
| Combined drops | Tropicamide plus phenylephrine | Faster, larger dilation | As above |
Cycloplegics (paralyse accommodation)
| Drug | Recovery | Main use |
|---|---|---|
| Cyclopentolate 0.5–1% | About 24 hours | Cycloplegic refraction in children and young adults |
| Atropine 0.5–1% | 7–14 days | Maximum cycloplegia (esotropia, high hyperopia); also amblyopia penalisation and uveitis |
| Homatropine 2% | 1–3 days | Uveitis; rarely refraction |
See cycloplegic refraction for technique and dosing in children.
Before dilating: safety checks
- Estimate the angle (van Herick or a torch shadow test); be careful in hyperopes over about 50 and those with a history of haloes or angle closure.
- Warn about blur and glare for about 4–6 hours and advise not to drive until vision returns; provide sunglasses.
- Ask about iris-clip lenses, allergies and heart disease (phenylephrine). Record the drug, strength, time and eye.
- If angle closure occurs after dilation (pain, haloes, red eye, high IOP), it is an emergency: refer at once. Reversing with pilocarpine is no longer routinely recommended after tropicamide-induced mydriasis.
Topical anaesthetics
| Drug | Onset and duration | Notes |
|---|---|---|
| Proxymetacaine (proparacaine) 0.5% | About 20 seconds; lasts 10–20 minutes | Least stinging; store in a fridge |
| Oxybuprocaine (benoxinate) 0.4% | Similar | Often combined with fluorescein for tonometry |
| Tetracaine (amethocaine) 0.5–1% | Stings more; longer | Used in procedures |
| Lidocaine 4% (with fluorescein) | Quick | Also used in combinations |
Never give anaesthetic drops for the patient to take home: repeated use causes toxic keratopathy and non-healing ulcers. Warn the patient not to rub the eye until sensation returns. Anaesthetics also slightly reduce tear production and affect TBUT and Schirmer results.
Diagnostic dyes
| Dye | Use |
|---|---|
| Fluorescein (strips or minims; 2% solution) | Staining, TBUT, applanation tonometry, RGP fit, Seidel test; stains soft lenses, so remove them first and wait before reinserting |
| Lissamine green | Conjunctival and corneal staining in dry eye |
| Rose bengal | Similar to lissamine green but stings; less used now |
| Fluorescein sodium IV and indocyanine green | Angiography by ophthalmologists (risk of anaphylaxis) |
Rules for safe use
- Use single-use minims where possible to avoid contamination (especially fluorescein, which can harbour Pseudomonas in multi-dose bottles).
- Check the drug name and expiry before instilling; cap colours (AAO) help but are not a substitute for reading the label.
- Punctal occlusion for 1–2 minutes reduces systemic absorption, important in children.
- Use only the drugs your registration and local regulations allow, and record consent and use.
Practical pearls
- Use tropicamide plus phenylephrine 2.5% for dark brown irides: tropicamide alone often gives poor dilation in Indian eyes.
- Always give the patient sunglasses and a written note of when dilation will wear off.
- If you ever see a patient using anaesthetic drops at home, stop them and refer: toxic keratopathy can blind.
Where students slip
- Dilating a patient with a very shallow anterior chamber without assessing the angle.
- Using phenylephrine 10% in infants or patients with heart disease.
- Putting fluorescein in with soft contact lenses in place.
Test yourself: flip cards
Quick quiz
Related: Dilating Eye Drops: Why Your Pupils Are Widened, Blur and Driving, Cycloplegic Refraction and Refracting Children: Drugs, Technique and Prescribing, Ocular Pharmacology: High-Yield Guide for Residents, Anterior Segment Examination for Optometrists: Grading Scales (Efron, CCLRU), Staining and van Herick, AAO Eye Drop Cap Colour Codes: All 13 Drug Classes. Back to the optometry curriculum.
Key sources
- Bartlett JD, Jaanus SD. Clinical Ocular Pharmacology. 5th ed. Butterworth-Heinemann; 2008
- College of Optometrists (UK). Guidance: use of drugs in optometric practice
- Pandit RJ, Taylor R. Mydriasis and glaucoma: exploding the myth. A systematic review. Diabet Med. 2000;17:693-699
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