Diagnostic Drugs Flashcards
what are mydriatics
used to dilate the pupil
why is there an increase in the use of mydriatics
- expansion of co management
- increase in professional negligence cases (eg ret detach missed)
- better appreciation of benefits of dilation
when to dilate
- conditions eg diabetes, uveitis, pigmented fundus lesion, suspect glauc, ht, amd, history of ret detach or metastatic cancer
- symptoms eg flashers, floaters, new distortion, unexplained loss of vision, recent blunt trauma
- relevant family ocular history
- small pupils, nystagmus, unsteady fixation
- systemic meds with potential side effects
mydriatics used by optoms
-tropicamide 0.5%
-tropicamide 1%
phenylephrine 2.5%
- all available in minims - good as its single use so sterile, and bad as generates plastic waste
college of optom guidelines when using any drug
- record the batch number, and expiry date of the drug
- record drug name, conc and time instilled, how many drops you put in each eye
- this facilitates verification that drug is in date, and in the case of a drug recall it makes it easier to trace all pxs who might have been affected
precautions before mydriasis
- explanation to px - why dilating, effects and duration
- previous exp of dilation
- medical history eg phenylephrine caution in px with cv disease and htn
- current meds
- measurement of iop
- assessment of risk of angle closure
what is acute closure glaucoma
= anterior chamber angle which aqueous flow through gets blocked
acute attack of acg = v painful red eye, cornea becomes hazy, can feel like a bad headache
- mydiratic drugs may cause increased risk of acute attack of acg
other points to note in the risk of mydriasis provoking an acute acg attack
- dilation facilitates evaluation of disc in cases of possible open angle glauc = useful to dilate these pxs
- if someone has a very narrow angle, should refer anyway as at high risk of acg attack at any time
- if px has suspected ret detach, wet amd etc and you cant obtain sufficient view, must either dilate
assesment of risk of angle closure
-van herick
-gonioscopy - contact method requires corneal anaesthesia
flash light test - not used
advice to px regarding mydriasis
- loss of acuity
- glare problems - px may benefit from wearing sunglasses
- driving diffs
- recognition of symptoms of an acute acg attack
- give info sheet
- give written and verbal info
tropicamide
- affects/ blocks parasynmpathetic system
- an anti muscarinic drug which causes mydriasis by relaxing the sphincter muscle of the iris and cycloplegia by relaxing the ciliary muscle
- onset of action = approx 10-30mins
- max effect = within approx 20-40 mns
- recovery to normal = approx 4-9hrs
- v few allergic reactions
- risk of acg in predisposed eye
pheylephrine
- mimics symp system
- a sympathomimetic drug which causes myriasis by dilating the dilator muscle of the iris
-mydriasis not complete - light reflex not abolished - can still get pupillary light reflexes
- may be used in combination w tropicamide in pxs who are diff to dilate
-onset of action = approx 10-30mins
max effect = approx 30-90mins
-recovery to normal = approx 5-12hrs
-contra indicated in conditions including vascular htn and long standin insulin dependent diabetes - should be used with caution in any diabetic, longstanding bronchial asthma and cerebral arteriosclerosis
cycloplegics
- used to produce or partial paralysis of ciliary muscle ie accom is disabled
- used if there are indications of fluctauting or excessive accom during refraction
- used mainly in kids when their accom is unstable making ret unreliable
- young latent hypermetropes (someone acc hyperopic but because theyre constantly accomodating you dont notice it)
- tropicamide and cyclopentolate is more effective at disabling accom in young people
cyclopentolate
- an anti muscarininc 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 mydriasis
- onset of action = 10-30mins
- max effect = approx 20-60mins
- recovery to normal = within 24hrs
- available in minims 0.5 and 1
- tend to use 1% minims in under 12s and 0.5% in kids aged 12 and over
- also consider iris colour
- more likely to get cns effects w cyclopentolate than w tropicamide
effect of iris colour (applies to all mydriatics and cycloplegics)
- drug binds with melanin on the iris and is slowly released
- in dark irides this leads to slower onset of action and longer duration of action
- applies to all mydriatics
