3.1.10 Uses diagnostic drugs to aid ocular examination.

What are mydriatic drugs and what are the two pharmacological drug groups?

- Drawn from the two pharmacological drug groups:

• anti-muscarinics and sympathomimetic

How is the size of the pupil controlled?

The size of the pupil is controlled by two opposing muscles in the iris:

• Sphincter pupillae (miosis)

  • Activated by parasympathetic nerve supply via muscarinic receptors

• Dilator pupillae (mydriasis)

  • Activated by sympathetic nerve supply via adrenergic receptors

What should be checked before using mydriatic drugs?

• Check AC angles (Van Herick Grade 1-2 are considered a risk)

  • Women, hypermetropes and East Asian patients are most susceptible to narrow angles

• Advise possible after effects, who to contact in case of an adverse reaction, no driving, glare

What is the risk associated with dilation and what are the risk factors?

• Dilation has a risk of angle closure glaucoma

• Risk factors: small eyes or narrow anterior chamber angles (from VH)

What should be done if angle closure glaucoma is suspected?

• ACG normally occurs in the recovery phase from dilation

  • Bc the mid-dilated pupil is in close apposition to the anterior surface of the lens (‘pupil block’)

• If you suspect someone of ACG, monitor IOP every 30 mins

• If after 3 readings it hasn’t gone down then EMERGENCY REFERRAL

What are the characteristics of tropicamide?

Available in 0.5% or 1%, POM

• Mydriatic action in 25 minutes

• Recovery in 5 hrs

• Higher iris pigmentation requires higher concentration

• Cycloplegic effect peaks at 20 mins and recovers around 3hrs (variable)

What are the characteristics of cyclopentolate?

• Available in 0.5% or 1%, POM

• <3 not recommended

• 3 months to 12 years = 1 drop of 1%

• Allow 40 minutes before carrying out refraction

• Allow 50D for ciliary tonus

• Focusing returns within 6-12 hours

• Adverse reactions rare (hypersensitivity usually shows in facial and upper body rash within 4-6 hours)

Tropicamide side effects

Photophobia, dry mouth, headache, dizziness, allergic reaction, irregular heartbeat, nausea and vomiting

Cyclopentolate side effects

Photophobia, eye itching, puffy eyelids

Serious - neurological symptoms, tachycardia, difficulty urinating, severe allergic reaction

What should be recorded when using mydriatic drugs?

• You must write down the true information: Name, concentration, dose, batch number and expiry date

• Check the patient hasn't had any reactions to drops previously - and is written down

• Note that you have explained to the patient how long the drops take to work, how long they last, any symptoms they may get

• Explain what symptoms they can get in terms of a reaction to the drops and what to do, ensure you have noted a patient information leaflet about the drops given

What are anaesthetic drugs and how do they work?

• Either amide or ester local anaesthetics. They block sodium channels in nerve cells, preventing nerve signals of pain.

  • Onset 10–30 seconds

  • Duration 10–20 minutes

What are the common side effects and precautions of anaesthetic drugs?

• Mild stinging upon instillation

• Corneal epithelial erosions

• Delayed wound healing

• Allergic reactions (more common with ester-type agents)

Avoid usage in suspected open-globe injuries.

Useful for contact tonometry, pachymetry and foreign body assessment

What are the characteristics of oxybuprocaine?

Available as 0.4%, POM

• Ester-type anaesthetic

• Minimal stinging

• Low incidence of allergic reaction

What are the characteristics of lidocaine?

Available as 4% with 0.25% NaFl, POM

• Amide-type anaesthetic (more stable and longer-lasting)

• Slower onset compared to ester-based drops

• Deeper anaesthesia than oxybuprocaine

• Lower allergic reaction potential than all other anaesthetics

What should be recorded when using anaesthetic drugs?

• You must write down the true information: Name, concentration, dose, batch number and expiry date

• Check the patient hasn’t had any reactions to drops previously - and is written down

• Note that you have explained to the patient how long the drops take to work, how long they last, symptoms they may get

• Explain what symptoms they can get in terms off a reaction to the drops and what to do, ensure you have noted a patient information leaflet about the drops given