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OV2004 clinical skills > introduction to diagnostic drugs > Flashcards

introduction to diagnostic drugs Flashcards

1
Q

what are mydriatic drugs?

A

mydriatics are used to dilate (open up) the pupil

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2
Q

why is there an increased use of mydriatics in optometric practice?

A
  • expansion of co-management (shared care) schemes
    e. g. gluacoma schemes for primary open angle glaucoma
  • increase in professional negligence cases
    e. g. missed retinal detachment
  • better appreciation of the benefits of dilation
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3
Q

when to dilate ?

A
  • conditions e.g. diabetes, uveitis, pigmented fundus lension, suspected glaucoma, peripheral retinal degeneration, hypertension (high blood pressure), cataract, age-related macular degeneration, history of retinal detachment, history of metastatic cancer
  • symptoms e.g. flashes and floaters, new distortion, unexplained loss of vision , recent blunt force trauma
  • relevant family ocular history
  • small pupils, nystagmus, unsteady fixation
  • where stereoscopic view of retina is necessary
  • systemic medications with potential side effects
  • to get good fundus photograph
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4
Q

explain the benefits of pupil dilation?

A
  • ability of ophthalmoscopy to grade correctly diabetic retinopathy is more than 50% higher through a dilated pupil than through an undilated pupil
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5
Q

what are the mydriatics used by optometrists?

A
  • Tropicamide 0.5%
  • Tropicamide 1.0%
  • phenylephrine 2.5%

. all available in minims - single use plastic files

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6
Q

what the college of optometrists guidelines when using a drug?

A
  • optometrists should record the batch number and expiry date of drugs that are used in their professional practice
  • also record drug name, concentration and time instilled
  • this will facilitate verification that:
    . drug is in date
    . in the case of a drug recall- makes it easier to trace all patients who may have been affected
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7
Q

what are the 4Ds when it comes to drugs?

A

drug
dosage
date( expiry )
disposal

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8
Q

what are precautions to take before mydriasis ?

A
  • explanation to patient
    . why dilating, effects and duration
  • previous experience of dilation
  • medical history
    . phenylephrine: caution in patients with cardiovascular disease, hypertension
  • current medication
  • measurement of IOP
  • assessment of risk of angle closure
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9
Q

the impact of mydriatic drugs on IOP?

A
  • small risk of increasing IOP and inducing angle closure gluacoma when using mydriatic drugs?
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10
Q

why is there a small risk of increasing IOP and inducing angle closure gluacoma when using mydriatic drugs?

A
  • angle closure gluacoma occurs when angle of drainage becomes blocked
  • when dilating the pupil, there is a risk of blocking the drainage angle
  • the region around the black arrowhead shows the front surface of the iris that has come into contact with the trabecular meshwork
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11
Q

what is the risk of mydriasis provoking an acute ACG attack?

A

1 - Baltimore eye survey ( cross sectional study) dilated approx 5000 subjects

. used 1% tropicamide / 2.5% phenylephrine

. No ACG episodes

. later gonioscopy( more detailed way of assessing the anterior chamber angle) judged 20 of theses to be at high risk

2- another study - systematic review
. tropicamide used alone( 0.5% or 1.0%)
. zero cases in 3972 dilations

. all other dilating agents

  • 33 cases in about 600,00 dilations
  • or 1 in 18,020

. dilating patients with primary open angle gluacoma
- zero cases in over 1000 patients

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12
Q

what are other points to note regarding the risk of mydriasis provoking an acute ACG attack?

A
  • dilation facilitates evaluation of disc in cases of possible open angle glaucoma i.e. is useful to dilate these patients
  • if someone has a very narrow ( potentially occludable) angle, should refer anyway as at high risk attack of ACG at any time
  • if patient has suspect retinal detachment, wet AMD and you cannot obtain sufficient view, must either dilate, or refer on worst case scenario
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13
Q

what are different ways to assess risk of angle closure?

A
  • Van herick
  • flashlight test
  • smith’s slit-length method
  • methods using pachymeters
  • gonioscopy
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14
Q

what to advice patients regrading mydriasis ?

A

1- loss of acuity
because
. depth of focus worsen when dilate pupil
. drugs relax accommodation

2- glare problems
. patient may benefit from wearing sunglasses
. patient may wish to bring sunglasses with them to the examination

3- driving difficulties

4- recognition of symptoms of an acute ACG attack

5- give information sheet

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15
Q

what is the advice regarding driving after dilation?

A
  • patients should be given an information sheet, and recommended not to drive for the rest of the day
  • college of optometrists information sheet says that ‘ it is recommended that driving should be avoided whilst your vision is affected
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16
Q

what is topicamide ?

A
  • an anti-muscarinic drug which causes mydriasis by relaxing the sphincter muscle of the iris and cycloplegia by relaxing the ciliary muscle
  • blocks the parasympathetic nervous system
  • onset action = approx 10 to 30 minutes
  • maximum effect=within approx 20 to 40 minutes
  • recovery to normal= approx
    4-9 hours
17
Q

how likely is an allergic reaction after tropicamide?

A
  • very few allergic reactions
  • only isolated adverse systemic reactions reported
    . CNS effects can occur with cyclopentolate
  • risk of ACG in predisposed eye
  • be careful of possible interactions with other anti-muscarinics
18
Q

what is phenylephrine ?

A
  • a sympathomimetic drug which causes mydriasis by stimulating the dilator muscle of the iris
  • mydriasis is not complete
  • light reflex is not abolished
  • may be used in combination with tropicamide in patients who are difficult to dilate
  • onset of action= approx 10 to 30 minutes
  • maximum effect= within approx 30 to 90 minutes
  • recovery to normal = approx 5 to 12 hours
19
Q

what are cycloplegics ?

A
  • drug used to produce ‘cycloplegia’

. paralysis or partial paralysis of ciliary muscle i.e. accommodation is disabled

20
Q

when is cycloplegics mostly used?

A
  • used if there are indications of fluctuating or excessive accommodation during refraction
  • used mainly in children when their accommodation is unstable, making retinoscopy unreliable
  • young latent hypermetropes
  • tropicamide and cyclopentolate are both cyclopegic agents, but cyclopentolate is more effective at disabling accommodation young people
21
Q

what is cyclopentolate?

A
  • an anti-muscarinic drug ( like tropicamide ) which causes cycloplegia by relaxing the ciliary muscle ( and mydriasis by relaxing the sphincter muscle of the iris)
  • used widely for cycloplegia , not as a mydriatic
  • consider iris colour

. onset of action = approx 10 to 30 minutes
. maximum effect = within approx 20 to 60 minutes
. recovery to normal = within 24 hours

22
Q

what is cyclopentolate available in ?

A
  • available in minims 0.5% and 1.0%

- tend to use 1% minims in under 12s and 0.5% in children aged 12 and over

23
Q

what are side effect of cyclopentolate?

A
  • more likely to get CNS effect with cyclopentolate than with tropicamide
24
Q

what are the effects of iris colour ( applies to all mydriatics and cycloplegics) ?

A
  • drug binds with melanin on the iris and is slowly released
  • in dark irides contain more melanin this leads to
    . slower onset of action
    . lower duration of action
  • this applies to all mydriatics
25
Q

what are local anaesthetics ?

A
  • used to anaesthetise the cornea and conjunctiva
26
Q

what are the two groups of local anaesthics?

A
  • ocular local anaesthetics ( ester type )

- ocular local anaesthetic ( amide typer )

27
Q

what are ocular local anaesthetics ( ester type)?

A
  • tetracaine ( amethocaine ) hydrochloride 0.5%
  • oxybuprocaine hydrochloride ( benoxinate ) 0.4%
  • proxymetacaine hydrochloride 0.5%
  • all are available in minims
28
Q

what is ocular local anaesthetics ( amide type)?

A
  • lidocaine 4%
  • may be used in case of previous toxic reaction to ester anaesthetics
  • all available in minims
29
Q

what are the characteristics of ocular local anaesthetics ?

A
  • complete anaesthesia within 1 minute ( usually 20 seconds)
  • sting on instillation
  • time for recovery of sensitivity is very variable
  • warn px no to rub eyes during this time
  • may cause a toxic reaction - check for staining before leaving
30
Q

what is the discomfort scale of local anaesthetic or saline control?

A
  • proxy stings less than ametha and benox
31
Q

what the effects of prior instillation of a local anaesthetic ?

A
  • corneal penetration of any other drug is increased
    . some optoms. instil a local anaesthetic before instilling tropicamide ( or phenylephrine ) to dilate the pupil
    . this gives a quicker response and can lead to a bigger pupil
32
Q

what is fluorescein?

A
  • used in:
    . contact applanation tonometry
    . contact lens fitting
    . assessing corneal damage
  • up until recently all optometrists used fluorets
33
Q

what is the availability of flurorets ?

A
  • in march 2013 bausch and lomb stopped the production of fluorets
    . flurorets were licensed as a medicine in UK
    . fluorescein minims are still available. But:
  • expensive
  • shorter shelf life
  • availability problem
  • fluorescein is available in paper strip from CE-marked as medical device (e.g. Bio-glo)

OV2004 clinical skills (12 decks)

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