L4 Mydriatics, Cycloplegics and Miotics Flashcards
how is mydriasis achieved?
stimulation of the dilator muscle (mainly alpha receptors)
paralysis of the sphincter muscle
How is dilation achieved through the SYMPATHETIC AND
PARASYMPATHETIC division?
SYMPATHETIC: ACTIVATED
PARASYMPATHETIC: DEACTIVATED
what is an example of a Adrenergic agonist / Sympathomimetic drug? what are 3 ocular side effects?
Phenylephrine (1 gtt 2.5% sol)
* Takes longer to reach max action: ~20-60 mins, does not affect accom
side effects:
*widening of palpebral aperture
– alpha receptors are present in the Muller muscle
- blanching of the conjunctival blood vessels,BV constricts
– alpha receptors are present in conj bv. - Accom effect??
what are 2 other clinical uses of phenylephrine? 4 precautions?
Other clinical uses:
* Breaking posterior synechiae
* Diagnostic test for Horner’s syndrome
precautions:
* Cardiac disease
* Hypertension
* Arteriosclerosis
* Hyperthyroidism (hypersensitivity)
Sympathomimetic Drugs
what is an example of a Cholinergic Antagonists/ Parasympatholytic /Anti muscarinic drug? what is the onset, recovery and how can it be reversed?
Tropicamide (1 gtt 0.5% or 1.0 % sol)
(NOTE: 1% solution can be used for highly pigmented iris.)
- Rapid in action: 15 mins
- Recovery ~ 2hrs
- Can be reversed c/2% pilocarpine (M agonist)
what are 2 precautions of tropicamide?
- Down’s syndrome (hypersensitivity)
- Brain Disorders
what are the 4 steps we must take prior to dilation?
- Estimate angle of anterior chamber
- Shadow test
- Van Herick technique
- Gonioscopy - Perform IOP check (tonometry) before & after dilation
- Have an appropriate miotic available
- History
* Episode of angle closure
– Must be taken to ensure that patient has NOT had
angle closure before.
* Known allergy to drug
* Presence of glaucoma (treated with miotics)
* Systemic drugs
* Systemic diseases, health condition
7 Signs & Sxs of AACG
- Blurry vision
- Nausea + vomiting
- Pain
- Ciliary flush
- Elevated IOP
- Fixed semi-dilated pupil
- Corneal edema
4 contraindications for mydriatics?
- A narrow angle or closed angle
- iris supported IOL
- subluxated crystalline lens or IOL
- Hx suggesting angle closure glaucoma
NOTE:
Each mydriatic would have individual contraindications
what is a common combination of dilating drugs?
Common combination:
* Tropicamide (0.5%) + Phenylephrine (2.5%)
May be indicated in:
– elderly pxs
– diabetic pxs
what are cycloplegics? why are not all cycloplegics mydriatics even though they cause pupil dilation?
All cycloplegics are antimuscarinic agents.
* Therefore, all cycloplegics cause
mydriasis….but not all mydriatics are
cycloplegics. because *Cycloplegics block postsynaptic muscarinic
receptors in the iris & ciliary body.
3 common cycloplegics, their max action and they recovery
- cyclopentolate (0.5-1.0%)
Repeat 5 mins between drops
– Max action: 20-30 mins
– Recovery: 12-24 hrs - Atropine (0.5-1.0%)
– Max action: 1 day
– Recovery: 7-10 days - Tropicamide (1.0%)
– Max action: 20-30 mins
– Recovery: 6 hrs
4 traits of atropine poisoning?
- Blind as a Bat
– Effect on accommodation - Dry as a Bone
– Inhibition of sweat gland - Red as a Beetroot
– Dilation of blood vessel(??) - Mad as a Hatter
– CNS effects : hallucinations, confusion
4 uses of cycloplegics?
- For when a px cannot relax the accommodation sufficiently.
– Binocular vision anomalies eg:squints
– Latent hyperopia
– Children < 6 yrs of age - Treatment of myopia
- Treatment of amblyopia
- Treatment of uveitis: relaxes ciliary muscle spasm & prevents posterior synechiae
2 Advantages of cycloplegics
- Associated mydriasis
– facilitates examination of fundus, DFE - Bruckner test, test red reflex