Ophthalmic Drugs Flashcards
Describe the sphincter pupillae muscles
Ring of smooth muscle fibres around the pupil that, when contracted constricts the pupil. Part of the parasympathetic system.
The sphincter pupillae muscles are part of which system?
Parasympathetic system with ACh as the neurotransmitter
Describe the dilater pupillae muscles
Thin layer of myoepithelium that extends from iris root to sphincter pupillae and when contracting allows for the pupil to dilate. Part of the sympathetic system.
The dilater pupillae muscles are part of which system?
Part of the sympathetic system. Noradrenaline as the neurotransmitter
What does the PNS do in relation to the eye?
Supplies the sphincter pupillae and ciliary muscle and constricts the pupil. It allows for accommodation.
What does the Sympathetic nervous system do in relation to the eye?
Supplies the dilator pupillae within the iris and dilates the pupil
What is the neurotransmitter in the PNS?
ACH is released from the nerve and binds to ACh receptors on the post-synaptic membrane.
Acetyl cholinesterase (enzyme) terminates the signal.
This is for nerve to nerve or nerve to muscle
What is the neurotransmitter involved in the sympathetic nervous system?
Noradrenaline
What is a parasympathomimetic drug?
It mimics ACh meaning it causes the action potential to be higher.
As it also is an agonist to the PNS it further increases the action potential
What is a parasympatholytic drug?
It’s an anti-muscarinic meaning that it blocks ACh and thus stops the action potential of the parasympathetic innervation (ACh) and thus is an antagonistic
What is a sympathomimetic drug?
Mimics noradrenaline in the sympathetic nervous system and so is an agronomic
What is a sympatholytic drug?
Blocks noradrenaline
What are the 4 names of ophthalmic drugs called?
Cycloplegic drugs, Mydriatic drugs, Miotic drugs and Local Anaesthetics
What are cycloplegic drugs?
They’re parasympatholytic meaning that they inhibit ACh and thus cause temporary paralysis of the ciliary muscle, no accommodation occurs (cycloplegia) and causes pupil dilation (mydriasis) because the sphincter muscle is inhibited.
When are cycloplegic drugs used?
For refraction in children and in myopia studies and are used to check the fundus
What are the 3 cycloplegic drugs?
Cyclopentolate, Atropine and Tropicamide
What is cyclopentolate?
It’s a cycloplegic drug that is the gold-standard for cycloplegia. It is faster-acting, non-toxic and doesn’t last long. It cannot be used for children <3mo but for between 3mo-12yo use 1% and then in >12yo use 0.5% quantities
What is atropine?
It’s a cycloplegic drug that comes from deadly nightshade. It is used in 1% quantities.
What is tropicamide?
It’s a cycloplegic drug that is most often used when wanting to dilate the pupil to check the fundus. it can also be used in refraction where there are allergies to cyclopentolate or atropine. Used in 0.5% or 1% quantities.
What are mydriatic drugs?
Causes mydriasis which is dilation of the pupil as it is a sympathomimetic which means it enhances the action of Noradrenaline in the sympathetic system and so causes the enhancement of the dilator pupillae.
When are mydriatic drugs used?
In adults for fundus exams.
Why would we use mydriatic drugs instead of cycloplegics?
Cycloplegic drugs all are mydriatic drugs (cause dilation of the pupil) but sometimes we want mydriasis without significant cycloplegia
What are the mydriatic drug?
Phenylephrine. It’s a sympathomimetic and agonist and not to be used in anyone with high blood pressure. it almost always uses 2.5% as the 10% version can impact the cardiovascular system.
What would we do if we wanted maximum mydriasis?
Use a sympathomimetic and an anti-muscarinic/parasympatholytic
What are miotic drugs?
They’re parasympathomimetic drugs meaning that they block the parasympathetic system ACh and so leads to miosis.
It can cause accommodative spasm and it opens the trabecular meshwork and improves aqueous drainage.
What are miotic drugs used in?
Previously used in glaucoma but this is rare now. Some now use as presbyopia correction by utilising the pinhole effect of the constricted pupil
What is an example of a miotic drug?
Pilocarpine Hydrochloride
What are local anaesthetics used in?
Applanation Tonometry which is the measurement of intraocular pressure, involves a prove onto the cornea
OR
used in Gonioscopy to view the anterior chamber
OR
used in the forced duction test
How are local anaesthetics used?
May be instilled prior to other drops as they reduce the stinging of cycloplegic drops, increase the effectivity of anti-muscarinic and patients must not rub eyes after as they scratch the corneal as unable to feel corneal sensations
How does iris pigmentation affect certain drugs?
It can take longer to dilate the eyes/achieve cycloplegia in individuals with brown irises as the iris can absorb some of the drug molecules opposed to going to the muscle site (Lovasik, 1986).
Either the dark pigment cells bind to the drug which reduces drug uptake OR the anterior limiting layer of the iris is formed of chromatophores in darker eyes this is thicker and more compact so may block drug uptake.
In a case history what do you need to take before administering an ophthalmic drug?
1) Current and previous general health issues
2) Current medications
3) Allergies
4) Whether they’ve had drops before and any adverse reactions to this
What information do you need to provide a patient if administering them ophthalmic drugs?
1) Effect of drops/ointment
2) Side effects (minor)
3) Adverse reactions & where to go if they occur
4) Provide leaflets if available
5) That if using drops/ointment at home then to stop taking them if side effects occur
E.g. mydriatic drugs may be troublesome for a child due to the amount of light.
How do we administer drops? Step-by-step
1) Wash hands
2) Gently pull down lower lid
3) If an adult, encourage them to look up
4) Drops into lower central fornix
5) Gently press on the tear duct area (punctual occlusion) as wanting to stop systemic absorption into the tear duct
6) Wipe away excess drops to prevent child getting drops on hands and putting fingers in mouth
7) Wash hands
How do we administer ointment (oculentum)? Step-by-step.
1) Wash hands
2) Gently pull down lower lid
3) Squeeze approx. 0.5cm of ointment into lower central fornix
4) Massage lids gently
5) Wipe away excess ointment
6) Don’t allow child to rub eye and put fingers in mouth
7) Wash hands
Why is ointment good in the night by less so during the day?
Good for long-lasting effects at night but it reduces VA
What do we need to write in our notes?
1) Drugs used
2) Dosage
3) If instilled in the clinic we need to ask which eye and what time
4) If instilled at home we need to give clear instructions, let them know which eye(s), when, how frequent and when to stop
5) Report any errors or near misses
Parasympathomimetic do what to the dilator, ciliary muscle and sphincter muscle?
Dilator - no effect
Ciliary Muscles - Enhances. Ciliary spasm, painful and blurred vision
Sphincter - Enhances (miosis)
LOOK AT SLIDES
Parasympatholytics/Anti-mucolytics do what to the dilator, ciliary muscle and sphincter muscle?
Dilator - no effect
Ciliary muscle - Blocks = lens wont change shape as ciliary muscle wont contract and thus results in cycloplegia (removal of accommodation)
Sphincter - Blocks = mydriasis (as the dilator isn’t affected and so has unopposed actions) and cycloplegia
Sympathomimetic’s do what to the dilator, ciliary muscle and sphincter muscle?
Dilator - Enhances (mydriasis as the dilator is the strongest over the ciliary and sphincter as it’s enhanced) Accommodation isn’t affected as it doesn’t affect the PNS.
Ciliary Muscle & Sphincter - No effect
Sympatholytic’s do what to do the dilator, ciliary muscle and sphincter muscle?
Dilator - Blocks = miosis as the sphincter muscle is unopposed
Ciliary Muscle & Sphincter - No effect
Which drug would you use in a 13yo for refraction and fundus media check?
0.5% Cyclopentolate
Which drug would you use in a 6mo for refraction and fundus and media check?
1% Cyclopentolate
Which drug would you use for a 3yo with very dark eyes for refraction?
Local anaesthetics first and then 20 mins later 1 drop of cyclopentolate, then 20 minutes after do examination
OR maybe start 1 drop cyclopentolate, wait 20 minutes and do another drop if it didn’t work
OR straight to atropine and wait a few hours
Which drug would you use for a 43yo for a fundus and media check?
Sympathomimetic - Phenylephrine (be aware of blood pressure history and general health with Pheny)
