cyclo refraction.dider
TRANSCRIPT
Syed Mohammed Didarul Alam
B.Sc in optometry (B.Optom)Faculty of Medicine
Institute of Community Ophthalmology
University of Chittagong
CYCLOPLEGIC REFRACTION
What is Cycloplegia?
• Cycloplegia means paralysis of the ciliary muscle which inhibits the accommodative power of the eye by blocking the action of the ciliary muscle.
• The best way to obtain paralysis of accommodation is to use cycloplegic drugs.
Principle of cycloplegic refraction
• Determination of total refractive error during temporary paralysis of ciliary muscles as an instillation of cycloplegic drugs & it is objective methods which is also known as wet retinoscopy
History
• Donders – 1864 “ Anomalies of accommodation and refraction of the eye”
• cyclopegics have been 1st used since middle of the 19th century to relax the accomodaton for the assesments of refractive error
• In 1950 atropine sulfate & homatropine hydrobromide are the cycloplegics choice.
Cycloplegic drugs
• Atropine sulphate• Homatropine• Tropicamide• Cyclopentolate HCl• Scopolamine HBr
Relax accomodation & inhibits the accommodative power of the eye
Inhibits the cholinergic stimulation of iris sphincter and ciliary muscle
Block the action of acetylcholine in CM receptors ( muscarinic)
Cycloplegic drugs ( anticholenrgic)
Cholinergic receptors• found in the iris sphincter and
the ciliary body. • It is of the muscarinic type also
found in the skeletal muscles. • Five sub types of muscarinic
receptors(M1-M5) • The muscarinic agonist action at
the receptor constricts the pupil & contracts the ciliary muscles.
• The inhibition causes pupillary dilatation & paralysis of accommodation
Indication for cycloplegic refraction
• Pediatric age group • Suspect and/or manifest strabismus (especially esotropia)• Accommodative esotropia• Intermittent esotropia• Infantile esotropia• Excessive accomodation• Suspected latent hyperopia• Suspected pseudomyopia• High Hypermetropia
Indication for cycloplegic refraction
• Significant anisometropia • Suspected accomodative anomalies• Uncooperative/noncommunicative patients• Variable and inconsistent end point of refraction • Amblyopic children• Psychiatric patient• Asthenopia • Cerebral palsy • Suspected malingering and hysterical patients
Contraindication
• Shallow anterior chamber with close angle
• Narrow angle glaucoma• Systemic anti-cholenergic
drugs receiver
Gauri S Shrestha, M.Optom, FIACLE
Selection and use of specific cycloplegic agents
Agent [C%] Dosage Max cycloplegic-effect
Duration of effect
Residual accom
Atropine sulfateHomatropine
0.5%,1%
2%
1D TID 3 days1D TID
3-6 hrs
1hrs
2-3 weeks
1-3days
Negligible
Negligible
Scopolamine HBR
0.25% 1D TID 60 mins 1-3 days Negligible
Cyclopentolate HCL
0.5%(birth- 3yr), 1%(>3yrs)
1D TID 30-45 mins
24 hrs minimal
Tropicamide HCL
0.5%, 1% 1D TID 20-30 mins
4-8 hrs moderate
Atropinization
• Natural alkaloid (Atropa belladonna)• Commercially available as the sulphate
derivative in 1% solution or 1% ointment• 1 Dosage TID- 3 days• Max cycloplegic effect within 3-6 hours• Recovery 2-3 weeks
Mode of action
• Act as antagonist of the muscarinic acetylcholine receptors
• Dampens the action of the parasympathetic nervous system
• Resulting cycloplegic & mydriatics effec
Clinical use
• Excessive accomodating children• suspected latent hyperopia• accommodative esotropia• Treatment of amblyopia- • Treament of uveitis,keratitis
Atropine may lead to complications• Fever• Dry mouth • Decrease Sweating• Decrease bronchial
secretions• Allergic reactions
of the eyelids and conjunctiva.
• Elevation of IOP• tachycardia• Convulsions &• even death
Homatropine
•One tenth as potent as atropine. •Shorter duration of mydriasis and
cycloplegia. •It is not the drug of choice for the
cycloplegic refraction because of its prolonged mydriatic and cycloplegic action.
Side Effect
• include incoherent Speech• Hallucinations• disorientation• psychosis &• visual disturbances.
cyclopentolate
• cyclopentolate 0.5% are used as opposed to 1% for infants
• This is because drug absorption through the conjunctival epithelium and skin is more rapid in infants compared to adults due to immature metabolic enzyme systems in neonates
• Faster onset of action and shorter duration of effect. • Cycloplegia occurs in 30-45 minutes of instillation• 1 drop & repeated within 5 min• 0.75D will be subtracted from retinosopic findings
Side Effect
Occular• Lacrimation • blurred vision• Hallucinations
Systemico Ataxia o Disorientationo Disturbance in
speech o Restlessness
Procedure
• Reduce the room illumination• The patient asked to look at the retinoscopic
light• Then neutralize the primary meridians &
neutralize the Refractive Error
What does our practice say?
• Advise atropine cycloplegic refraction invariably in the children younger than 3 years
• Advise atropine cycloplegic refraction in esotropic children (accommodative type) up to 4 years
• After 4 years, advise cyclopentolate cycloplegic refraction up 25-30 years
• Above 30 years, check amplitude and lag of accommodation, then advise cycloplegic refraction
– If full cycloplegia has been achieved then normal tonus of the CM will also relaxed & it will reach 3/4D & due to CM tonus 1D should subtracted
– In Myopia it is not necessary to subtracted but in hyperopia it is necessary.
Spectacle prescribing
• Prescribing spectacle from cycloplegic finding is an art rather precise science
• How to prescribe spectacle? – Concept of emmetropization is necessary– Esotropic children younger than 4 years, full
refractive correction(maximum plus) is prescribed–With older children, amount of plus can be reduced
till fusion is maintained
Post mydriatic treatment (PMT)
•Assessment of the finding of cyclorefraction by subjective means after the effect of cycloplegia is eliminated.
•If atropine is used ciliary tonus should be subtracted.
•Not necessary in the case of cyclopentolate.
References
• Primary Care Optometry• Clinical Procedure Of Optometry• Clinical Ophthalmology- Jack J Kanski• American Academy of Optometry (AAO)• Pediatric Ophthalmology & Strabismus - AOA• Internet