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OV3017 Eye Disease > 5 - Mydriatics > Flashcards

5 - Mydriatics Flashcards

1
Q

why do we use mydriatics

A

more thorough examination
- examination of crystalline lens, vitreous + fundus

  • for treatment of eye conditions e.g uveitis, stops iris sitcking to lens
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2
Q

when to use

A
  • 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
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3
Q

ideal properties of mydriatic

A
  • rapid onset
  • adequate duration
  • fast recovery
  • no associated cyclopegia or side effects
  • light reflex abolished
  • no rise in IOP
  • easily reversed in emergency
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4
Q

prior to dilation?

A
  • good reason
    -explain procedure
  • px consent
  • issue written info + adverse effects
  • check for contraindications
  • record 4D’s
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5
Q

general contraindications

A
  • known hypersensitivity to drug
  • narrow angles
  • symptoms of CAG or diagnosed with CAG
  • px using pilocarpine for glaucoma treatment
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6
Q

what is the risk associated with tropicamide (low)

A

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

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7
Q

how to minimise risk of CAG in 4 ways

A
  1. IOPs pre and post dilation
  2. Check anterior angles
  3. Existing symptoms?
  4. Use of a miotic drug (not usually used in practice)
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8
Q

2 categories of mydriatic drugs

A
  1. muscarnic antagonists (antimuscarinics/anticholinergic)
  2. sympathomimetic (alpha agonist)
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9
Q
  1. muscarnic antagonists
A

**-block acetylcoA on muscarinic receptors **
tropicamide - most common
- cyclopentalate - rarely used as mydriatic
- atropine - only availbile for IP

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10
Q
  1. sympathomimetic
A

phenylephrine - more used in USA

enhancing noradrenalin effects on alpha1 adrenoreceptors

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11
Q

Autonomic nervous system refresher

A
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12
Q

what is the inner circular muscle

A

iris sphincter muscle (pupillary constrictor)

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13
Q

what is the role of the iris sphincter muscle in inducing mydriasis

A

parasympathetic stimulation causes contraction of the iris sphinctor muscle
and contraction of the pupil

blocking Ach causes dilation = tropicamide

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14
Q

what is the outer circular muscle

A

iris dilator muscle (pupillary dilator)

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15
Q

role of iris dilator muscle in inducing mydriasis

A

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

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16
Q

anti muscarinic action

A
  • 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
17
Q

Sympathomimetic action

A

neurotransmtter is noradrenalin -neurohumeral transmitter at most sympathetic post ganglionic neuro-effector junctions except sweat glands + vasodilator fibres on skeletal muscle

18
Q

what receptors does noradrenalin have

A
  • mainly alpha 1 receptors in dilator pupillae muscle
  • alpha 1 excitatory, alpha 2 inhibitory
  • beta 1 excitatory beta 2 inhibitory
19
Q

what receptor is phenylephrine

A

selective alpha 1 adrenergic. acting on the iris dilator muscle

20
Q

differences between tropicamide and phenylephrine

A
21
Q

tropicamide - P or POM?

A

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

22
Q

side effects of tropicamide

A
  • transient stinging/blurring
  • photophobia
  • raised IOP (possibly)

after prolonged administration:
- irritiation
-oedema
- hyperaemia
- conjunctivitis

general body: dry mouth: kids

23
Q

phenylephrine - P or POM

A

P

24
Q

phenyl ephrine : single or multi use

A

single use

  • Single use Minims (Bausch & Lomb) 2.5%
  • Phenylephrine HCL 10%
  • Phenylephrine HCL
  • Store at 25°C, protect from light
25
Q

who is 10% phenylephrine not recommended for

A

children + elderly due to increased risk of systemic toxicity

26
Q

what is phenylephrine less effective on

A

highly pigmented eyes

27
Q

phenylephrine may cause widening of palpebral aperture OR

A

blanching of the conjuncitva
- vasoconstriction of conjuncitval blood vessels

28
Q

what are the contraindications of phenylephrine

A
  • medication - cardiovascular problems, depression
  • thyrotoxicosis
  • insulin dependant diabetes
  • asthma
  • pregnancy/lactation
  • use of pilocarpine
29
Q

ocular side effects of phenylephrine

A
  • transient stinging/blurring
  • photophobia
  • lid retraction
  • conjunctival allergic reaction
  • punctate keratitis
30
Q

general body side effects of phenylephrine

A
  • palpitaitons
    -tachychardia
  • cardiac arhythmias
    -hypertension
    -headaches

drug gains access to systemic blood supply

31
Q

what are some Synergistic combinations

A

Combinations of antimuscarinic and sympathomimetics can be considered (e.g. Tropicamide 0.5% and Phenylephrine 2.5%)

  • lower conc of anti muscarinic used = less cyclo effect
32
Q

What is mydriasert

A

POM
- insoluble insert
- contains phenylephrine and tropicamide
- gradual release
- surgical conditions
- in adults insert up to 2 hours before procedure
- remove within 30 mins of mydriasis

33
Q

cyclopentolate is a

A

anti muscarinic

  • cycloplegia
34
Q

homatropine is a

A

antimuscarnic

  • mydriatic effect commences in 10-20 mins,
  • both light and accommodative reflexes absent
  • recovery can take up to 3 days

OV3017 Eye Disease (19 decks)

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