7.1.2. Uses appropriate diagnostic drugs to aid refraction. Flashcards
Indications of cycloplegic drugs
- Cycloplegic refraction
- Children with unexplained poor VA
- Children with poor stereopsis
- Children with an esophoria or manifest esotropia to indicate if fully accommodative
- Children with over or underactive accommodation
- Children of parents with high hypermetropia or squint
- Dilating the pupil in anterior uveitis, for alleviation of ciliary spasm following corneal abrasion
- Penalisation therapy in amblyopia
Contraindications
Hypersensitivity to cyclopentolate or any component of the preparation.
Contraindicated in patients with confirmed or suspected angle closure in whom an acute attack may be precipitated.
Cautions
Children (age 3 months to 12 years): for cycloplegic refraction: one drop of 1% solution to each eye. Observe for 45 minutes after instillation. DO NOT do in infants under 3 months
Darkly pigmented irises are more resistant to pupillary dilation and caution should be taken to avoid overdosage.
Multidose aqueous preparations contain benzalkonium chloride and should not be used when soft contact lenses are worn. Contact lenses should be removed prior to application and the patient should wait at least 15 minutes before re-insertion.
There are no adequate well-controlled studies of cyclopentolate in pregnant women. Cyclopentolate should not be used in pregnancy unless the benefit clearly outweighs the risk to the developing fetus. It is not known whether cyclopentolate is excreted in breast milk, thus it should be used with caution during breast-feeding.
Interactions
The effect of antimuscarinic agents may be enhanced by the concomitant administration of other drugs with antimuscarinic properties, such as amantadine (antiviral), some antihistamines, butyrophenones, phenothiazines and tricyclic antidepressants.
Use & Supply
POM: For use and supply by all optometrists.
- Available preparations
Mydrilate: eye drops, 0.5% cyclopentolate hydrochloride (Intrapharm Laboratories Ltd)
Mydrilate: eye drops, 1.0% cyclopentolate hydrochloride (Intrapharm Laboratories Ltd)
Single use (preservative-free) - Minims Cyclopentolate: eye drops, 0.5% cyclopentolate hydrochloride (Bausch & Lomb UK Ltd)
Minims Cyclopentolate: eye drops, 1% cyclopentolate hydrochloride (Bausch & Lomb UK Ltd)
Classification & Mode of Action
Antimuscarinic
Cyclopentolate blocks the receptors in the muscles of the eye (muscarinic receptors). These receptors are involved controlling the pupil size and the shape of the lens. Cyclopentolate thus induces relaxation of the sphincter of the iris and the ciliary muscles. When applied topically to the eyes, it causes a rapid, intense cycloplegic and mydriatic effect that is maximal in 15 to 60 minutes; recovery usually occurs within 24 hours.
Sideeffects (Ocular & Systemic)
- Ocular sideeffectstransient stinging
transient blurring
photophobia
raised intraocular pressure
conjunctival hyperaemia
conjunctival oedema. - Systemic sideeffectsCNS disturbances - (ataxia - less balance & coordination, incoherent speech, restlessness, hallucinations, hyperactivity, and disorientation) - toxicity reaction!!
dry mouth
flushing
tachycardia
urinary symptoms e.g. retention
gastrointestinal symptoms. - How to reduce systemic absorptionSystemic absorption may be reduced by compressing the lacrimal sac at the medial canthus during - and for 2–3 minutes after - instillation of the drops.
Storage
Store below 25°C (Mydrilate at 2–8°C).
Protect from light.
How long does drug affect last/work?
Takes 30-40 minutes to work & lasts up to 24 hours
How to carry out the procedure
- Must get VCG from guardian if child & child doesn’t have capacity to consent
- Explain why you are doing the procedure. Assessor may ask you to explain how you would say it to a child
- Explanation:
- “Young children like Max have a very good ability to adjust the focus of their eyes compared to adults, almost like a camera coming in & out of focus”
- “In Max’s case, the focussing power of his eyes keeps changing, making it difficult to get an accurate reading of his prescription”
- “What I’d like to do is use some eye drops prevent this from happening as easily. These drops may cause Max to be more light sensitive, he might notice things up close being more blurred & his pupils will be bigger”
- “The side effects generally last for a few hours & the drug can take up to 24 hours to fully leave his system”
- “I’ve got a leaflet for you to read in regards to what to expect. Has Max had any bad reactions to eyedrops previously or have any allergies?”
- “Will all that being said, are you OK with me using the drops?”
Cycloplegic Refraction
- If px not accommodating then don’t need them to look at distance target like normal ret. They can look at the light from your ret if needed
- Worth retting one meridian then the other with no trial frame or working distance. Subtract WD at the end to both meridians then transpose.
- For example: +3.00 x 90 / +5.00 x 180 WD = 50cm = +2.00D
- Subtract WD = +1.00 x 90 / +3.00 x 180
- Tranpose = Most positive as sphere = +3.00
- Difference of powers as cyl = -2.00
- Axis is of most positive meridian = 180
- Therefore answer is = +3.00/-2.00 x180
How do you know the drug has worked?
- Max pupil dilation. If unequal between eyes then unequally used cyclo
- Stable ret reflex. If they stare at the ret light and it isn’t stable then cyclo not deep enough
Random: What are the potential sideeffects of Atropine?
Blind as a bat (paralysis of accommodation)
Dry as a bone (inhibition of sweat glands and salivary glands)
Red as a beetroot (dilatation of skin blood vessels)
Mad as a hatter (CNS effects, hallucinations and ataxia)
CNS effects occur only in advanced stages of atropine poisoning, milder effects occur at
an earlier stage, so the patient will be thirsty, hot and dry, have a dry mouth, and they
will have an increased heart rate.
The patient must be taken to casualty IMMEDIATELY.
