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Eye disease and therapeutics > Mydriatics > Flashcards

Mydriatics Flashcards

1
Q

Why would you use mydriatics

A
  • 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
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2
Q

What sort of patients would you use mydriatics on

A
  • 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)
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3
Q

What are the ideal properties of a mydriatic

A
  • 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
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4
Q

What should you do before dilating the px

A
  • 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
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5
Q

What is the 4 D drug test

A

-Drug
-Dosage
-Date
-Disposal
-And time instilled

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6
Q

Process of dilating px eyes

A

increasing the likelihood of causing systemic signs and symptoms)

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7
Q

What do you record when dilating pupils using mydriatics

A
  • 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
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8
Q

What are some contraindications of using mydriatics

A
  • 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
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9
Q

What happens in closed angle claucoma

A
  • Build up of pressure in anterior chamber
  • Trabecular meshwork closed off - angle closed off
  • Pupil block causing angle closure
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10
Q

Signs and symptoms of closed angle glaucoma

A
  • Blurred vision
  • Haloes
  • Headache
  • Painful
  • Vomiting/nausea
    -Photophobia
    -Sudden increase in IOP ( usually >40mmHg)
  • Conjunctival hyperaemia
  • Cloudy cornea
  • Fixed mid-dilated pupil
    -Closed angle
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11
Q

How can you minimise risk of CAG

A

-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

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12
Q

What are the pre dilation measurements

A
  • Van Herrick
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13
Q

Van Herick’s Technique

A
  • 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
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14
Q

Examples of mydriatic drugs

A

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

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15
Q

Autonomic Nervous System pathways transmitter, receptor and muscle

A

Parasympathetic:
- Transmitter = Acetylcholine
- Receptor = Muscarinic
- Muscle = ciliary and sphincter

Sympathetic:
- Transmitter = Noradrenaline
- Receptor = Alpha
- Muscle = Dilator

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16
Q

Role of sympathetic pathway

A

‘fight or flight’

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17
Q

Role of parasympathetic pathway

A

Inhibits body from overworking

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18
Q

How does tropicamide cause dilation

A
  • 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
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19
Q

How does Phenylephrine cause dilation

A

-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

20
Q

What is action of antimuscarinics

A
  • 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
21
Q

What are other words for antimuscarinics

A
  • Muscarinic antagonist
  • Anticholinergic
22
Q

What is action of sympathomimetics

A
  • 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 –
23
Q

wHWhat sort of drugs is in

A
24
Q

What sort of drugs is in Sympathomimetic pathway t

A

Adrenergic drugs

25
Q

What type of drug is Phenylephrine

A

A selective alpha 1 –adrenergic receptor activator acting on the iris dilator muscle

26
Q

What is the trasnmitter in sympathetic nervous system

A

Noradrenaline

27
Q

What muslce is controlled by parasympathetic nervosus system

A

Iris sphincter

28
Q

Features of tropicamide

A

*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

29
Q

Features of phenylephrine

A

*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

30
Q

How is tropacimade available

A

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

31
Q

What is POM

A

Prescription only medicine

32
Q

When is 1% tropicamide used and what can that cause

A
  • For darker irides
  • But will also lead to an increased cycloplegic effect
33
Q

Who should you avoid using tropicamide in

A
  • Pregnancy – avoid if possible, but better than using Phenylephrine.
  • Women who are using Tropicamide must not breast- feed.
34
Q

Side effects of tropicamide

A

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 )

35
Q

How is phenylephrine available what form

A
  • P medicine = pharmacy
    Single use:
    • Minims (Bausch & Lomb) 2.5%
      -Phenylephrine HCL 10% phenylephrine HCL
    • Store at 25°C, protect from light
36
Q

Who shouldnt you use 10% phenylephrine in and why

A
  • 10% Phenylephrine is contraindicated in children and the elderly (>65 years)
  • Because of the increased risk of systemic toxicity.
37
Q

Who is Phenylephrine less effective on

A

Highly pigmented eyes

38
Q

What can Phenylephrine cause in eye

A

-Widening of palpebral aperture
- Blanching/whitening of the conjunctiva – vasoconstriction of conjunctival blood vessels

39
Q

What can Phenylephrine cause in eye

A

-Widening of palpebral aperture
- Blanching/whitening of the conjunctiva – vasoconstriction of conjunctival blood vesselsWw

40
Q

What test is used to differentiate between Scleritis and Episcleritis

A

If eye white or red after putting tropicamide in

41
Q

Contraindications of Phenylephrine- who do you need to be careful for

A
  • 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
42
Q

Side effects of Phenylephrine

A

Ocular:
- Transient stinging
- Transient blurring
- Photophobia
- Lid retraction
- Conjunctival allergic reaction
- Punctate keratitis
General- body:
■Palpitations
■Tachycardia
■Cardiac arrhythmias
■Hypertension
■Headaches

43
Q

What are synergestic combinations

A
  • Use of two or more substances to provide an effect greater than the sum of their separate effects
44
Q

Example of synergestic combinations and why use it

A
  • 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
45
Q

Features of mydriasert

A
  • 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
46
Q

Other mydriatic drugs

A

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

Eye disease and therapeutics (9 decks)

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