Mydriatics Flashcards
What is the purpose of mydriatics?
Pupil dilation
(also treats anterior uveitis)
What can the effectiveness of mydriatics be influenced by?
Increased age - smaller pupil won’t dilate as much
Iris colour - darker irides have slower responses
Drug type, dose, contact time
What are the mechanisms of mydriatics?
Sympathomimetic (direct alpha-1 adrenergic agonist)
Antimuscarinic (direct muscarinic antagonist)
What is the mechanism of phenylephrine?
Sympathomimetic
Direct agonist to dilator muscle - mimics norepinephrine and binds with receptors on adrenergic receptor making dilator contract
What is the mechanism of tropicamide?
Antimuscarinic
Antagonist to cholinergic muscarinic receptor, blocks Ach from binding at cholinergic receptor making sphincter relax
What is the dose for phenylephrine?
1-2 drops, 2.5%, 5 min interval if instilling more
What is the dose for tropicamide?
1-2 drops, 0.5%/1%, 5 min interval if instilling more
What is the onset and recovery for phenylephrine?
Onset: 50-60 mins
Recovery: 2-18 hours
What is the onset and recovery for tropicamide?
Onset: 5-30 mins
Recovery: 2-18 hours
What are the contraindications for phenylephrine?
Cardiac disorders
V high BP
Stroke history
T1 diab
Pregnancy
Already taking adrenergic agonists or monoamine oxidase inhibitors
What are the contraindications for mydriatics?
Known hypersensitivity
Known angle-closure
Narrow angles
Iris-mounted IOLs
Which patients should you take caution with when using mydriatics?
Pregnant patients
CL wearers (contamination)
What advice should you give to patients receiving tropicamide drops?
Stings on instillation
Blurred vision for a few hours - unable to drive
Bring sunnies as it can make things brighter and experience more glare
