Mydriatics Flashcards
Why do we use mydriatics?
Field of view doing techniques such as direct is small and so a midriatic can be used to increase this.
- 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 are indications that we should dilate to have a view of the fundus?
• Patients at risk of retinal detachment:
Those with –High myopia (>-5.00 D), family history of retinal detachment , trauma
•Or if they present with any of the following symptoms:
–Unexplained vision loss/visual fields loss/disturbance
–Floaters,
- flashes,
- veil of vision/curtain
- shadows
- for screening purposes for diabetics
- Inadequate fundus view –Lens/media opacities –Miotic pupils (less than 2mm)
What are the 4Ds when using a drug?
State the Druge, Dose , Date , Disposal
What should you do prior to inserting a mydriatic?
Explain procedure
Px consent: • Issue written information Advise effects- glare, loss of stereo vision, driving, operating machinery
Minimise risk of adverse reaction
Check for contraindications
How do you insert a mydriatic?
Ask the patient to look up:
- Pull down lower lid
- Instil one drop into lower conjunctival sac
- Occlude puncta – avoids drug draining into the nasolacrimal duct thereby (i) reducing the effectiveness of the drug in the eye and (ii) increasing the likelihood of causing systemic signs and symptoms)
- Record drug, strength, dosage, expiry date, batch number and time of instillation
What are contrandications for using a mydriatic?
Known hypersensitivity to drug e.g. px hypersensitive to tropicamide
- 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)
What are signs and symptoms of a closed angle glaucoma attack?
Sudden red eye- conjunctival hyperemia
Sudden increase in IOP
Cloudy Cornea
Fixed mid-dialted pupil
Closed angle
Blurred vision
Haloes
Headache
Painful
Vomiting/nausea
How can we minimise the likelihood of a closed angle glaucoma attack?
Take pressures before and after dilating - so we are acc aware the IOP is rising and can treat sooner.
Check anterior angles
Use a miotic drug?
When would we refer in regards to pressures following a mydriatic?
If there is a significant rise in pressures that does not fall.
If there is an asymetric rise in pressures between eyes.
Give four examples of mydriatics
Tropicamide
Cyclopentolate
Atropine
phenylephrine
Give examples of muscarinic mydriatics
Tropicamide –Most commonly used
Cyclopentolate –Rarely used as a mydriatic
Atropine –Only available to independent prescribers –Unlikely to be used as mydriatic
Give an example of a sympathomimetic mydriatic
Phenylepherine –Used more in USA
How does tropicamide work?
It is a muscarinic antagonist - it blocks acetyl choline getting to muscarinic receptors in the parasympathetic branch of the autonomic nervous system - specifically on the ciliary and sphincter muscles.
How does phenylephrine work?
In the sympathetic branch of the autonomic nervous system - it mimicks noradrenaline on alpha receptors on the dilator muscle.
Describe how the iris muscles work to either dilate or constrict the pupil - describing the different branches of the autonomic nervous system each muscle falls under
What effect does inhibition of the parasympathetic nervous system cause?
mydriasis cycloplegia reduced tear secretion
What are the two types of receptors in the sympathetic nervous system and which one does phenylephrine work on?
Alpha and beta receptors •Mainly alpha 1 receptors in dilator pupillae muscle
Phenylephrine is a selective alpha 1 –adrenergic receptor activator acting on the iris dilator muscle
Describe the similarities and differences of using phenylephrine vs tropicamide to dilate
What doses does tropicamide come in?
0.5% and 1% minims
as well as multi-dose containers
On whom do we use 1% tropicamide and what side effect does this also cause?
1% sometimes used for darker irides, but will also mean also lead to an increased cycloplegic effect
What is the guidance regarding pregnancy and dilation?
Pregnancy – avoid if possible, but better to use tropicamide than phenylephrine
What is the guidance regarding tropicamide and breast feeding?
Women who are using Tropicamide must not breastfeed
What are the ocular side effects of tropicamide?
- Transient stinging
- Transient blurring
- Photophobia
- Raised IOP?
- After prolonged administration:
Irritation Hyperaemia Oedema Conjunctivitis
What are the systemic side effects of using tropicamide?
•CNS effects Dry mouth Reported in children (blue eyes,
What does is phenylephrine available in?
2.5 and 10% minims.
Why is the use of 10% phenyl ephrine contraindicated in children and over 65s?
because of the increased risk of systemic toxicity.
True or False - phenylephrine is less effective on highly pigmented eyes
True
True or False- phenylephrine causes blanching of the conjunctiva – vasoconstriction of conjunctival blood vessels
True - and in a non mydriatic application this can be useful for determining between scleritis and episcleritis
What are contraindications for using phenylephrine?
Medication- cardiovascular problems (e.g. Anti hypertensives, Tachycardia)
Medication-depression (e.g. Monoamine oxidase inhibitors, Tricyclic antidepressants)
Thyrotoxicosis
Insulin dependent diabetes
Asthma
Pregnancy/lactation-may cause transient fetal hypoxia
Use of pilocarpine–> Older px = pupil block Young px = accommodative spasm
What are ocular side effects of phenylephrine?
Transient stinging Transient blurring Photophobia Lid retraction Conjunctival allergic reaction Punctate keratitis
What are systemic side effects of phenylephrine?
■Palpitations ■Tachycardia ■Cardiac arrhythmias ■Hypertension ■Headaches
Why do we have to be careful of drug interactions?
Synergistic combinations - Use of two or more substances to provide an effect greater than the sum of their separate effects
What is a mydriasert?
New high tec meidcine :
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
Is cyclopentolate a mydriatic?
yES
What dose is cyclopentolate available in and what other effect does it have other than dilating?
It acts as a cycloplegic - blocking accommodation - 0.1%
Describe homatropine
It is an anti-muscarinic
Mydriatic effect commences in 10-20 mins
Maximal mydriasis 30-40 mins
Both light and accommodative reflexes absent
Recovery can take up to 3 day
