5 - Mydriatics Flashcards
why do we use mydriatics
more thorough examination
- examination of crystalline lens, vitreous + fundus
- for treatment of eye conditions e.g uveitis, stops iris sitcking to lens
when to use
- when px is at risk of retinal detatchment, high myopia, history, trauma
- symptoms such as unexplained vision loss/ field disturbance, flashes/floaters. shadows
- screening for diabetes
- inadequate fundus view
ideal properties of mydriatic
- rapid onset
- adequate duration
- fast recovery
- no associated cyclopegia or side effects
- light reflex abolished
- no rise in IOP
- easily reversed in emergency
prior to dilation?
- good reason
-explain procedure - px consent
- issue written info + adverse effects
- check for contraindications
- record 4D’s
general contraindications
- known hypersensitivity to drug
- narrow angles
- symptoms of CAG or diagnosed with CAG
- px using pilocarpine for glaucoma treatment
what is the risk associated with tropicamide (low)
Blurred vision
Sudden increase in IOP (usually >40mmHg)
Haloes
Headache
Painful
Vomiting/nausea
Conjunctival hyperaemia
Cloudy cornea
Fixed mid-dilated pupil
Closed angle
Photophobia
Emergency — know what to do
how to minimise risk of CAG in 4 ways
- IOPs pre and post dilation
- Check anterior angles
- Existing symptoms?
- Use of a miotic drug (not usually used in practice)
2 categories of mydriatic drugs
- muscarnic antagonists (antimuscarinics/anticholinergic)
- sympathomimetic (alpha agonist)
- muscarnic antagonists
**-block acetylcoA on muscarinic receptors **
tropicamide - most common
- cyclopentalate - rarely used as mydriatic
- atropine - only availbile for IP
- sympathomimetic
phenylephrine - more used in USA
enhancing noradrenalin effects on alpha1 adrenoreceptors
Autonomic nervous system refresher
what is the inner circular muscle
iris sphincter muscle (pupillary constrictor)
what is the role of the iris sphincter muscle in inducing mydriasis
parasympathetic stimulation causes contraction of the iris sphinctor muscle
and contraction of the pupil
blocking Ach causes dilation = tropicamide
what is the outer circular muscle
iris dilator muscle (pupillary dilator)
role of iris dilator muscle in inducing mydriasis
sympathetic stimulation of the adrenergic receptors causes the contraction of the iris dilator muscle and subsequently dilation of the pupil
- pretends to act as noradrenaline ; phenylephrine
anti muscarinic action
- iris sphincter muscle is controlled by parasympathetic innervation
- paralysis of parasympathetic nervous system inhibits the action of ACH released at post ganglionic nerves
- produces
- mydriasis
- cycloplegia
- reduced tear secretion
Sympathomimetic action
neurotransmtter is noradrenalin -neurohumeral transmitter at most sympathetic post ganglionic neuro-effector junctions except sweat glands + vasodilator fibres on skeletal muscle
what receptors does noradrenalin have
- mainly alpha 1 receptors in dilator pupillae muscle
- alpha 1 excitatory, alpha 2 inhibitory
- beta 1 excitatory beta 2 inhibitory
what receptor is phenylephrine
selective alpha 1 adrenergic. acting on the iris dilator muscle
differences between tropicamide and phenylephrine
tropicamide - P or POM?
POM for use and supply by all optoms
single use minims
(Bausch & Lomb) 0.5%
Tropicamide HCL 1.0% Tropicamide HCL Store below 25°C
multi dose containers
Multi-dose containers
Mydriacyl (Alcon) 0.5%
Tropicamide HCL (Alcon) 1.0%
Store 2 - 8°C (room temp)
protect from light
1% for dark irides, but will also lead to an increased cycloplegic effect
Pregnancy- avoid if possible but better than using phenylephrine
women who are using tropicamide must not breast feed
side effects of tropicamide
- transient stinging/blurring
- photophobia
- raised IOP (possibly)
after prolonged administration:
- irritiation
-oedema
- hyperaemia
- conjunctivitis
general body: dry mouth: kids
phenylephrine - P or POM
P
phenyl ephrine : single or multi use
single use
- Single use Minims (Bausch & Lomb) 2.5%
- Phenylephrine HCL 10%
- Phenylephrine HCL
- Store at 25°C, protect from light
