Mydriatics Flashcards
Why would you use mydriatics
- Enables a more
thorough
examination of the
eye: e.g. peripheral
crystalline lens,
vitreous, fundus - Facilitates a stereo
fundus
examination - For treatment e.g.
uveitis – stops iris
sticking to lens
What sort of patients would you use mydriatics on
- Patients at risk of retinal
detachment
–High myopia (>-5.00 D),
family history, trauma - Symptoms of….
–Unexplained vision
loss/visual fields
loss/disturbance
–Floaters, flashes, veils,
shadow - Screening
–Diabetics, high
myopia, prior to ocular
surgery - Inadequate fundus view
–Lens/media opacities
–Miotic pupils (less than
2mm)
What are the ideal properties of a mydriatic
- Rapid onset
- Adequate duration – long
enough to complete
investigation - Fast recovery
- No associated
- Cycloplegia
- Adverse effects
-Light reflex abolished - No rise in intraocular pressure
- Easily reversed in an emergency
What should you do before dilating the px
- Have a good reason to use the drug
- Explain procedure to px
- Px consent = issue written information
- Advise effects- glare, loss of stereo vision, driving, operating machinery
- Minimise risk of adverse reaction
- Check for contraindications
What is the 4 D drug test
-Drug
-Dosage
-Date
-Disposal
-And time instilled
Process of dilating px eyes
increasing the likelihood of causing systemic signs and symptoms)
What do you record when dilating pupils using mydriatics
- Drug name
- Drug strength
-Drug dosage
-Drug expiry date
-Drug batch number
-Time of instillation - E.G 1 drop 1% tropcamide instilled R & L at 4pm 08/14 FN3906
What are some contraindications of using mydriatics
- Known hypersensitivity to
drug - ask px - Iris clip IOLs – not common
- Narrow angles?
- Patient with symptoms
suggestive of sub-acute or
chronic closed angle
glaucoma (CAG) - Patient with diagnosed CAG
- Px using pilocarpine for
glaucoma treatment (constricts pupil which opens up drainage channels)= don’t want to use mydriatics in these px’s
What happens in closed angle claucoma
- Build up of pressure in anterior chamber
- Trabecular meshwork closed off - angle closed off
- Pupil block causing angle closure
Signs and symptoms of closed angle glaucoma
- Blurred vision
- Haloes
- Headache
- Painful
- Vomiting/nausea
-Photophobia
-Sudden increase in IOP ( usually >40mmHg) - Conjunctival hyperaemia
- Cloudy cornea
- Fixed mid-dilated pupil
-Closed angle
How can you minimise risk of CAG
-IOP – take pre and post dilation
–Significant rise in IOP/asymmetric rise –Monitor rises in IOP
–Refer to Eye Casualty if continues to rise
Check anterior angles
–Gonioscopy, Van Herrick, others
Existing symptoms?
–Ask if already has signs of angle closure e.g. haloes around lights, painful eye
Use of a miotic drug
–Not generally used in optometric practice
What are the pre dilation measurements
- Van Herrick
Van Herick’s Technique
- Used to estimate anterior chamber depth
- Microscope normal to corneal apex
- Illumination at 60 degrees to microscope
- Narrow slit beam 1mm
- Low magnification
- Compare width of anterior
chamber to width of corneal section
Examples of mydriatic drugs
Muscarinic antagonists/ antimuscarinic/anticholinergic:
- Tropicamide = most commonly used
- Cyclopentolate = rarely used as a mydriatic
- Atropine = only available to independent
prescribers, unlikely to be used as mydriatic
Sympathomimetic/ alpha agonist:
- Phenylepherine = used more in USA
Autonomic Nervous System pathways transmitter, receptor and muscle
Parasympathetic:
- Transmitter = Acetylcholine
- Receptor = Muscarinic
- Muscle = ciliary and sphincter
Sympathetic:
- Transmitter = Noradrenaline
- Receptor = Alpha
- Muscle = Dilator
Role of sympathetic pathway
‘fight or flight’
Role of parasympathetic pathway
Inhibits body from overworking
How does tropicamide cause dilation
- Inner circular muscle = iris sphincter muscle = pupillary constrictor
- Parasympathetic stimulation causes contraction of the iris sphincter muscle and constriction of the pupil
- This blocks Ach which causes dilation
How does Phenylephrine cause dilation
-Outer radial muscle = iris dilator muscle = pupillary dilator
- Sympathetic stimulation of the adrenergic receptors causes the contraction (shortening) of the iris dilator muscle and subsequently dilation of the pupil – ‘pretends’ to act as Noradrenaline
What is action of antimuscarinics
- Iris sphincter muscle is controlled by parasympathetic innervation
- Paralysis of parasympathetic nervous system inhibits the action of Ach liberated at postganglionic nerves
- This produces mydriasis, cycloplegia and reduced tear secretion hence dry eyes after instillation
What are other words for antimuscarinics
- Muscarinic antagonist
- Anticholinergic
What is action of sympathomimetics
- Noradrenaline is the transmitter in the sympathetic system
- Neurohumoral transmitter at most sympathetic
postganglionic neuro-effector junctions
Exceptions
*Sweat glands
*Vasodilator fibres on skeletal muscle - Alpha and beta receptors
*Mainly alpha 1 receptors in dilator pupillae muscle
*Alpha 1 excitatory, alpha 2 inhibitory
*Beta 1 excitatory, beta 2 inhibitory NB –
wHWhat sort of drugs is in
What sort of drugs is in Sympathomimetic pathway t
Adrenergic drugs
What type of drug is Phenylephrine
A selective alpha 1 –adrenergic receptor activator acting on the iris dilator muscle
What is the trasnmitter in sympathetic nervous system
Noradrenaline
What muslce is controlled by parasympathetic nervosus system
Iris sphincter
Features of tropicamide
*Mydriasis ~ 15 mins
*Recovery 8-9 hours
*Light reflex absent
*Induces a mild cycloplegic effect
*May cause rise in IOP but likely to be transitory
*Few contraindications
Features of phenylephrine
*Slower action ~30mins *Lasts approx. 12-24 hours
*Light reflex retained *Accommodation retained
*Less likely to produce rise in IOP as sector mydriasis
*Numerous contraindications
How is tropacimade available
POM for use and supply by all optometrists
Single use
- Minims (Bausch & Lomb) 0.5%
-Tropicamide HCL
-1.0% Tropicamide HCL Store below 25°C
Multi-dose containers
-Mydriacyl (Alcon)
-0.5% Tropicamide HCL (Alcon) 1.0%
-Tropicamide HCL (Alcon) Store 2 - 8°C, protect from light
What is POM
Prescription only medicine
When is 1% tropicamide used and what can that cause
- For darker irides
- But will also lead to an increased cycloplegic effect
Who should you avoid using tropicamide in
- Pregnancy – avoid if possible, but better than using Phenylephrine.
- Women who are using Tropicamide must not breast- feed.
Side effects of tropicamide
Ocular
*Transient stinging
*Transient blurring
*Photophobia
*Raised IOP?
*After prolonged
administration = Irritation, Hyperaemia, Oedema Conjunctivitis
General- body
*CNS effects Dry mouth = reported in children (blue
eyes )
How is phenylephrine available what form
- P medicine = pharmacy
Single use:- Minims (Bausch & Lomb) 2.5%
-Phenylephrine HCL 10% phenylephrine HCL - Store at 25°C, protect from light
- Minims (Bausch & Lomb) 2.5%
Who shouldnt you use 10% phenylephrine in and why
- 10% Phenylephrine is contraindicated in children and the elderly (>65 years)
- Because of the increased risk of systemic toxicity.
Who is Phenylephrine less effective on
Highly pigmented eyes
What can Phenylephrine cause in eye
-Widening of palpebral aperture
- Blanching/whitening of the conjunctiva – vasoconstriction of conjunctival blood vessels
What can Phenylephrine cause in eye
-Widening of palpebral aperture
- Blanching/whitening of the conjunctiva – vasoconstriction of conjunctival blood vesselsWw
What test is used to differentiate between Scleritis and Episcleritis
If eye white or red after putting tropicamide in
Contraindications of Phenylephrine- who do you need to be careful for
- Medication- cardiovascular problems (e.g. Anti hypertensives, Tachycardia)
- Medication-depression (e.g. Monoamine oxidase inhibitors, Tricyclic antidepressants)
- Thyrotoxicosis = excess of throid hormone
- Insulin dependent diabetes Asthma
- Pregnancy/lactation-may cause transient fetal hypoxia
- Use of pilocarpine
- Older px = pupil block
- Young px = accommodative spasm
Side effects of Phenylephrine
Ocular:
- Transient stinging
- Transient blurring
- Photophobia
- Lid retraction
- Conjunctival allergic reaction
- Punctate keratitis
General- body:
■Palpitations
■Tachycardia
■Cardiac arrhythmias
■Hypertension
■Headaches
What are synergestic combinations
- Use of two or more substances to provide an effect greater than the sum of their separate effects
Example of synergestic combinations and why use it
- Combinations of antimuscarinic and sympathomimetics can be considered (e.g. Tropicamide 0.5% and Phenylephrine 2.5%)
- Allows lower concentrations of antimuscarinic to be used = less cyclo effect
Features of mydriasert
- POM
- Insoluble ophthalmic
insert - Contains phenylephrine and tropicamide
- Gradual release
- Used pre-operatively and
diagnostically - In adults-insert up to max. 2 hours before procedure. Remove within 30 mins of mydriasis and within 2hrs of application
Other mydriatic drugs
Cyclopentolate (antimuscarinic)
- Used to be available in 0.1%
- Cycloplegic effect
Homatropine (antimuscarinic)
- Mydriatic effect commences in 10-20 mins - Maximal mydriasis 30-40 mins
- Both light and accommodative reflexes absent - Recovery can take up to 3 days
