Mydriatics, Cycloplegics and miotics Flashcards
why may mydriatics be used in medicine?
-pupil dilation
-ophthalmologists may use them in inflamed eyes and anterior uveitis treatment
give 3 factors that affect effectiveness of mydriatics
-drug, dose and contact time
-patient age
-iris colour
name 2 mydriatics
phenylephrine and tropicamide
what is the mechanism of action for phenylephrine? How does it work?
sympathomimetic
by acting as a direct alpha1-adrenergic agonist causing the iris dilator to contract
what is the mechanism of action of tropicamide and how does it work?
anti muscarinic
by acting as a direct anti muscarinic antagonist causing iris sphincter to relax
what is the onset and duration of phenylephrine?
50-60 minute onset
2-18hr duration
what is the onset and duration of tropicamide?
50-30 minute onset
2-18hr duration
what are the 2 ways phenylephrine is avaliable?
- MINIMS Preservative-free single dose eye
drops in 2.5% or 10% - Phenylephrine 10% in multidose bottle
what are the two ways tropicamide is avaliable?
- MINIMS in 0.5% or 1 %
- Mydriacil 1 % bottle
what drug combines phenylephrine and tropicamide and in what quantities?
Mydriasert: Phenylephrine 5.4mg +
tropicamide 280 micrograms
gives a slow release and gets instilled into the conjunctival sac. Advantage is its preservative free and doesnt need a large dose to take effect. This drug is not often used in optometry.
who might not be able to have mydriatics?
-pregnant patients
-soft CL wearers
what patients should you not use mydriatics on?
-those with known cases of hypersensitivity
-cases of known angle closure
-exceptionally narrow angles
-those with iris mounted IOLs
what should you warn patients of before instilling tropicamide?
-it stings on instillation
-causes blurred vision for up top 24hrs after
-glare
what patients might you not use phenylephrine on?
those with:
-known cardiac disorders
-history of stroke or very high BP
-type I diabetics
-taking adrenergic agonists or monoamine oxidase inhibitors
-pregnancy
what is the difference between mydriatics and cycloplegics?
mydriatics are dilating drugs that affect the iris sphincter or dilator whereas cycloplegics are drugs that affect the ciliary body by relaxing it hence reducing the ability to accommodate so some mydriatics will cause cycloplegia whereas all cycloplegics cause mydriasis
what are miotics?
drugs that cause pupil constriction
what is the mechanism of action for all cycloplegics?
anti-muscarinic so cholinergic antagonist
when may you use cycloplegics?
-cycloplegic refraction
-suspected accommodative esotropia
what are the 4 cycloplegics in order of strongest to weakest
1.atropine
2.homatropine
3.cyclopentolate
4.tropicamide
what are the 2 formulations of atropine
minims 1%
bottles 1%
whats the onset and duration of atropine?
onset = 30mins to several hours
duration = gradual recovery over 24 hours to 1 week
how should you use atropine 1% drops?
1 drop morning and evening for 2 days prior to examination and then 1 drop on the morning of the exam
what can you use atropine for apart from as a dilator?
-uveitis treatment
-treatment of myopia
-treatment of amblyopia
how can atropine be used for uveitis treatment?
-by relaxing ciliary muscle spasms relieving the pain associated with inflammation
in turn causing pupil dilation which prevents posterior synechiae
what are the adverse drug reactions (ADRs) of atropine?
- Dry throat (thirst)
- Decreased sweating
- Dry skin, flushing
- Tachycardia (racing pulse)
- Constipation, death, etc. etc.
what is the formulation of cyclopentolate?
- Minims 0.5% and 1%
- Bottles “Mydrilate” 0.5% and 1%
+ benzalkonium chloride (preservative)
how do you use cyclopentolate?
a total of 2 drops of 1% cyclopentolate with a 5 min interval between them
what is cyclopentolate used for?
cycloplegic refraction
what is the onset and duration of cyclopentolate?
- Onset : 30 mins
- Duration: gradual recovery
over 24 hours
what are the adverse reactions of cyclopentolate
“CNS effects”
* disorientation
* hallucinations
* rapid speech
* uncontrolled limb movements
* collapse
who has tropicamide been suggested to be used on?
- myopic adult refractive surgery patients (Hofmeister et al. 2005 J
Cataract Refract Surg 31:694-700) - non-strabismic infants aged 4-7 months (Twelker & Mutti 2001 Optom
Vis Sci 78:215-22)
why is tropicamide unlikely to produce sufficient cycloplegia in children?
because children have high amounts of residual accommodation
how do you use tropicamide?
two drops of 1% solution with a 5-min interval between each drop
what is the onset and duration of tropicamide
- Onset: 30 min
- Duration: 6 hrs
on instillation of homatropine, when does maximum cycloplegia occur how long is duration
Maximum cycloplegia occurs in 30–60 minutes and may last
1–2 days
what is ciliary muscle tonus?
the normal resting state of ciliary effort and accommodation in pre presbyopes
what adjustment do you need to make for ciliary muscle tonus in cycloplegic refraction using atropine?
Subtract 1.00 Dioptre
what adjustment do you need to make for ciliary muscle tonus in cycloplegic refraction using homatropine and cyclopentolate?
subtract 0.50D or none
what adjustment do you need to make for ciliary muscle tonus in cycloplegic refraction using tropicamide
subtract none
what are the 3 possible mechanisms of action for miotics?
-direct cholinergic agonist
-indirect cholinergic agonist
-adrenergic antagonist
what is the formulation of pilocarpine?
-minims 2%
-bottles 1% 2% and 4%
what is the onset and duration of pilocarpine 1%
-10 mins maximal at 30 mins
-duration 6 hrs
what are mitoics used for?
-reversal of mydriasis
-emergency management of acute closed-angle glaucoma
-long term glaucoma
whats pilocapine’s mechanism of action and how does it work?
-direct acting cholinergic agonist
- opens spaces within trabecular meshwork
- increase in rate of aqueous humour outflow from the eye
- expands the Schlemm canal
IOP gets reduced by stimulation and contraction of ciliary muscle
what are the side effects of pilocarpine ?
-spasm of accommodation due to direct stimulation of the ciliary muscle making it intolerable in patients under 40
-pupil miosis due to direct stimulation of iris sphincter muscle
-frontal headache
-chance of pupil block and subsequent angle closure
-retinal detachment risk
-systemic side effects
how can pilocarpine trigger retinal detachment?
- Chronic contraction of ciliary muscle places traction on vitreous and retina
- Increases risk of retinal tear and subsequent detachment
what patients does pilocarpine put at risk of pupil block or angle closure?
patients with narrow AC angle and/or a thick nuclear sclerotic
crystalline lens
what patients should you be careful of giving pilocarpine to?
- Known hypersensitivity
- Uveitis
- Iris-mounted IOLs
- History of iridectomy or retinal detachment
