Cycloplegic Refraction Flashcards
What are the common used cycloplegic agents?
- Atropine
- Homatropine
- Scopoalamine
- Cyclopentolate (0.5% and 1.0%)
- Tropicamide (0.5% and 1%)
What are cycloplegic drugs?
Anti-muscarinic agents which block the muscarinic actions of acetylcholine (PNS) in the iris and ciliary body.
Accordingly, they produce cycloplegia (loss of accommodative function) and mydriasis (pupillary dilation)
What is scopoalamine also used for?
Motion sickness
What is atropine also used for?
To control myopia
In which situations should you cycloplege?
- Pt can’t fixate steadily ie: Kids
- Ocular deviations (ESOtropia) since that is accommodative in origin
- More plus power found on retinoscopy than subjective refraction
- Amplitude of accommodation does not fall within normal limits for patient’s age
- Symptoms from refraction that aren’t eliminated by Rx
- Ambylopia
- Latent Hyperopia
- Pseudomyopia
What is latent hyperopia?
Hyperopia masked by accommodation
What is pseudomyopia?
Too much time accommodating then you can’t relax it
Ie: Studying
What are the possible symptoms from refraction that aren’t eliminated by Rx?
Transient blurring
Horizontal Diplopia
Head aches after near work
What are disadvantages of cycloplegic refraction?
- Increased aberrations from dilated pupil on retinoscopy essential to consider only the central part of the reflex
- Difference between shape of crystalline lens under cycloplegia and that under natural viewing conditions
- Atropine poisioning
- Angle closure -> Increased IOP
- Photophonia
- Decreased near function or distance for hyperopes
- Allergy
What is adequate cycloplegia defined as?
Amp of accommodation <2D
What is the time of onset and duration of atropine?
Onset: 3-6hrs
Duration: 10-18days
What is the time of onset and duration of Homotropine?
Onset: 30-60 min
Duration: 24-48 hrs
What is the time of onset and duration of scopoalamine?
Onset: 30-60min
Duration: 7 days
What is the time of onset and duration of Cyclopentolate?
Onset: 20-45min
Duration: 8-24hrs
What is the time of onset and duration of Tropicamide?
Onset: 20-30mins
Duration: 4-8hrs
