cycloplegic refraction By Dr Abid ..pptx

Cyclopegic refraction by Dr abid

1. Cycloplegic refraction

2. What is cycloplegia It is paralysis of the ciliary muscle of the eye, resulting in the loss of accommodation Accommodation is the ability of the lens to change its refractive power to view the near object. It is brought about by the contraction of the cillary muscles.

3. Normal Process Acetylcholine(Ach ) stimulate the ciliary muscles →Contraction →accommodation. Ach stimulate the iris sphincter →Contraction →Miosis After Cycloplegic drugs Ach muscarinic action is blocked . This leads to relaxation of cillary muscles Causes inhibition of iris sphincter contraction →pupil dilates

4. Cholinergic receptor

5. Parasympathetic system in the eye

6. Cycloplegic are drugs that paralyze the ciliary muscles and cause relaxation of accommodation. Once the ciliary muscles are relaxed, the anterior zonules stretch, and posterior zonules lose tension leading to thinning of the lens. This allows the eye to be relaxed and helps in focusing on distance . Cycloplegic drugs are the anticholinergic agents that block acetylcholine's muscarinic action in ciliary muscle receptors. This inhibits the cholinergic stimulation of the iris sphincter and ciliary muscles, allowing relaxation of accommodation and inhibiting the accommodative power of the eye . The various cycloplegic agents are atropine sulfate, homatropine hydrobromide , cyclopentolate hydrochloride, and tropicamide.

7. cycloplegic refraction Children and adolescents have strong accommodative capacity which can mask hyperopia or introduce a Pseudo- myopic shift in measurements. Cycloplegia is necessary to accurately assess their refractive status. Remains the gold  standard for determining refractive errors in children, and it is achieved by using pharmacologic agents that temporarily paralyze the ciliary muscle. Active accommodation in children is the primary source of error in measurements , M any studies on the pediatric population have shown that a lack of cycloplegia may result in an overestimation of myopia and an underestimation of hyperopia .

8. Indication For pediatric patients with S trabismus A mblyopia A nisometropia S uspected latent hyperopia The Refractive Errors also notes that near-vision should be assessed before cycloplegia in patients with high hyperopia or presbyopia, to capture any accommodation-dependent component.

9. Infants & young children → Atropine (strong accommodation, high hyperopia risk ). School children → Cyclopentolate (most widely used ). Quick clinic exam → Tropicamide.

10. Atropine Sulphate Anticholinergic drug. Mechanism of Action: Competitive inhibitor of acetylcholine at muscarinic receptors . Acts on structures innervated by post-ganglionic parasympathetic fibers. Causes paralysis of sphincter pupillae (→ mydriasis) and ciliary muscle (→ cycloplegia). non-selective muscarinic antagonist most potent mydriatic and cycloplegic agent Topical ophthalmic drops/ointment available in 0.01%, 0.5%, 1%, and 3% concentrations. Clinical Use in Refraction: For cycloplegic refraction, 1% atropine ointment is applied as a morning dose for 3 days .

11. Cyclopentolate Hydrochloride Anticholinergic drug. Formulations: A vailable in 0.5% and 2% strengths , 1% (commonly used). Mechanism of Action: Blocks muscarinic receptors at the sphincter pupillae and ciliary muscle. Produces mydriasis and cycloplegia . Pharmacological Features: Onset: Cycloplegia occurs within 30–45 minutes of instillation. Administration: One drop, repeated after 10-20 minutes . Duration: Effect lasts 6–18 hours (shorter than atropine). Tonus Allowance: A correction of 0.75 D is subtracted from the retinoscopy value to compensate for residual accommodation. Cyclopentolate is widely preferred for cycloplegic refraction in children because of its faster onset and shorter duration compared to atropine.

12. Tropocimide Anticholinergic drug. Formulations: Available in 0.5% and 1% sterile ophthalmic solutions . Mechanism of Action: Blocks muscarinic acetylcholine receptors of the sphincter pupillae and ciliary muscle. Causes mydriasis and, in higher strength, cycloplegia . Onset: Fast acting. 0.5% preparation: Produces mydriasis with minimal cycloplegia . 1% preparation: Produces mydriasis and significant cycloplegia . Duration : Short-acting compared to atropine and cyclopentolate. Effect on Iris Pigmentation: Pupillary dilatation is less affected by iris color (works well even in dark irides ). Clinical Uses: Diagnostic mydriasis (fundus examination). Cycloplegia for refraction (short-acting). Pre- and post-operative mydriasis (e.g., cataract surgery, laser procedures ). Clinical Note: Tropicamide is commonly used because of its powerful mydriatic effect, rapid onset, short duration, and low side effect profile .

13. Agent Selection & Strength Atropine remains the strongest cycloplegic and is especially used in cases of accommodative esotropia to reveal full hyperopic error. Because of its prolonged action and greater side effects, atropine is less commonly used routinely. Cyclopentolate 1% is widely considered a standard balance of efficacy and safety for routine pediatric cycloplegia. Tropicamide 1% may be used in children without strabismus or high hyperopia; some studies show similar final cycloplegic refraction when using tropicamide, with shorter recovery time. In dark-iris patients or cases needing deeper blockade, adding atropine or repeating doses may be necessary .

14. Contraindication P atients with the shallow anterior chamber close angle-closure glaucoma history of allergy or hypersensitivity to any component of drugs S ystemic anticholinergic drugs receiver Atropine gets absorbed systemically through the lacrimal sac and thus should be avoided in children as far as possible

15. It is advisable to compress the lacrimal sac for a minute after topical application to prevent systemic absorption. Though uncommon, few local side effects reported with atropine include, the allergic reaction of lids and conjunctiva, crusting of lid margins, and dryness of periocular skin.

16. Frequency & Follow-up Repeat cycloplegic refraction at intervals, especially during ocular developmental years. The frequency depends on age, change in refractive error, and presence of amblyopia or strabismus. For children < 3 years, refraction may be repeated every 6 months; for older children, annually, unless there is rapid refractive change. Reassess alignment, binocular vision, and vision following optical correction (especially in strabismus / amblyopia) at each visit.

17. Feature Atropine Cyclopentolate Tropicamide Class Anticholinergic (muscarinic blocker) Anticholinergic (muscarinic blocker) Anticholinergic (muscarinic blocker) Available strengths 0.01%, 0.5%, 1%, 3% (drops/ointment) 0.5%, 1%, 2% 0.5%, 1% Onset of action Slow (hours) Moderate (30–45 min) Fast (20–30 min) Duration Very long ( 7–14 days ) Intermediate ( 6–18 hrs ) Short ( 4–6 hrs ) Cycloplegia strength Very strong (maximum) Moderate to strong Mild (mainly at 1%) Mydriasis strength Strong Strong Strong (but shorter lasting) Tonus allowance 0.50 D 0.75 D ~0.25 D or negligible Main uses - Cycloplegic refraction in young children with high accommodation- Amblyopia penalization- Uveitis (prevent synechiae) - Routine cycloplegic refraction in children- Diagnostic cycloplegia - Fundus examination (short mydriasis)- Short cycloplegia when needed- Pre- & post-operative dilation Advantages Strongest, reliable cycloplegia Faster & shorter than atropine, safer in children Fast, short, low side effects, iris-color independent Disadvantages Very long recovery, risk of toxicity, not convenient Can cause stinging, transient irritation, occasional CNS effects in kids Weak cycloplegia (not reliable for full refraction in kids)