9. Mydriatics, Cycloplegics & Mitosis 2 Flashcards
Mechanism of action of all cycloplegic drugs? And they act on?
Mechanism: Antimuscarinics
Act on: Ciliary muscle and iris sphincter- Relax ciliary muscle that will relax the accommodation.
Most common choice of cycloplegic drug in optometry is?
Cyclopentolate
Conc used for cyclopentolate?
0.5% and 1%- 1% used for children
What preservative is used in cyclopentolate bottles?
How to identify if solution has degraded?
Benzalkonium chloride
When solution degrades it turns brown.
Clinical use of cycloplegics?
Cycloplegic refraction
Typical dose of cyclopentolate used for 3-5 year old’s vs children over 12?
3-5: 1% with 5 minute intervals inbetween.
Over 12: 0.5% used.
Her conc in age 3-5 because they have strong accommodation that needs to be relaxed.
Pharmacokinetics of cyclopentolate
Onset: 30 minutes
Duration: Gradual recovery over 24 hours
How to avoid CNS effects?
Occlude nasal punctata by PXs after installing drops in
ADRs with cyclopentolate?
- CNS effect
- Disorientation
- Hallucination
- Rapid speech
- Uncontrolled limb movement
- Collapse
This effects are self-limiting.
Why is tropicamide preferred by Px’s?
Better recovery from blurred vision.
Tropicamide is not the choice of drug used for cycloplegic refraction, why?
It is unlikely to produce sufficient cycloplegia in children- it does not get rid of enough amplitude of accommodation.
Dose, onset and duration of tropicamide
Dose: 1% with 5min intervals
Onset: 30mins
Duration: 6 hours
Is homatropine available readily?
Ordered specifically, not readily avaiable.
Extra qualification needed to use this drug.
Dose, onset and duration of Homatropine?
Dose: 1%
Onset: 30-60mins
Duration: 1-2 days
Slow recovery, long dilation
What is residual accommodation?
Amount of accommodation left after cyclopic drug is put in the eye.
Homatropine is not useful for cycloplegic refraction, why?
Because it has long lasting effects
Relation between strength of cycloplegic drug ad residual accommodation?
Strong cycloplegic drug– small value of residual accommodation.
What is the tonus?
This is the resting state of ciliary effort and accommodation in pre-presbyopes.
Is ciliary muscle tonus part of the refractive error?
No
Can cycloplegics abolish the strength of tonus ?
Depends on the strength of the drug
How is an allowance made to the refractive error of ciliary muscle tonus allowance?
Why is this done?
ADJUSTMENT TO THE SPHERE:
Atropine: Subtract 1D
Homatropine & Cyclopentolate: Subtract none or 0.50D
Tropicamide : None
WHY: To take into account the resting tonus that is regained when effects of the drug have worn off.
Effect of cycloplegic drugs on muscle tonus?
Cycloplegic drugs temporarily paralysis ciliary muscles depending on how strong the drug is hence, allowance for the tonus is made to the spherical RX.
Tonus is dependent on?
The refractive error
What do miotic drugs do?
Constrict the pupil
