Cycloplegic Refraction Flashcards
What is the mechanism of cycloplegic drugs?
Cycloplegic drugs are anti-muscarinic agents that block the muscarinic actions of acetylcholine (parasympathetic NS) in the iris and ciliary body
Provide cycloplegic (loss of accommodation) and Mydriasis (pupillary dilation)
What are the 5 commone cycloplegic agents?
Atropine
Homatropine
Scopolamine
Cyclopentolate (0.5% and 1.0%)
Tropicamide (0.5% and 1%)
Wha are 4 scenarios in which we would perform a cycloplegic refraction?
Patient unable to fixate steadily
Ocular deviations (esotropia) that appear to be accommodation in origin
Much (>1D) more plus power (or less minus) found on retinoscopy than subjective refraction
Amplitude of accommodation does not fall within normal limits for the patients ages
Rx does not fix symptoms
Apparent amblyopia
Latent hyperopia
Pseudomyopia
How can we distinguish a pseudomyope from a hyperope?
Appears to be myopic but isn’t
Blurry vision at the end of the day or after prolonged near work
What are some advantage of cycloplegic refraction?
Makes latent refractive errors manifest
Allows refractive assessment without any accommodation fluctuation
Avoids off axis retinoscopy errors
Allows dilated Fundus exam
What are some disadvantages of cycloplegic refraction?
Lens changes shape
Increased aberrations from dilated pupil on retinoscopy (must consider central reflex)
Mydriasis may include angle closure leading to increased intra-ocular pressure
With atropine, possibly of systemic poisoning on young children
Photophobia, decreased DV or NV
Allergy
Difficulty in deciding what to prescribe
What is considered to be an adequate cycloplegia?
Adequate cycloplegia is generally defined as an amplitude of accommodation of less than 2D
What acronym can be used for cycloplegic agents?
The car has sped away
(Shortest to longest onset)
What is the onset and duration for atropine solution?
3-6 hrs
10-18 days
What is the onset and durations for Homatropine?
30-60 min
24-48 hours
What is the onset and duration of scopolamine?
30-60 min
Up to 7 days
Why is the onset and duration of cyclopentolate?
20-45 min
8-24 hours
What is the onset and duration of tropicamide?
20-30 min
4-8 hours
What are 3 pre-dilation precaution that but be taken in all adults and co-operative pediatric patients?
History (Have they ever been dilated before? Family glaucoma?)
Tonometry
Assessment
How many drops are given for adults and teens dilation?
2 drops 5 min apart
