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
Describe the similarities and differences of using phenylephrine vs tropicamide to dilate
