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Pupil

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Information about Pupil
Health & Medicine

Published on March 3, 2014

Author: hindalshawadify

Source: slideshare.net

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Pupil

• The pupil is an rounded opening located in the center of the iris that allows light to enter the retina. • Its function is to control the amount of light entering the eye and it does this via contraction (miosis) and dilation (mydriasis) under the influence of the autonomic nervous system

The Pupil - Characteristics  Range of pupil diameters  Day light: 2.5 - 4.0 mm  Extremes: 1.3 - 10 mm  Anisocoria - unequal diameters.

Pupil Responses  Light:  Direct: light in OD right pupil constricts  Indirect (consensual): light in OD left pupil constricts  Near response: pupils constrict for near vision (due to accommodation and convergence)  Sensory/emotional  Drugs with autonomic actions:  Miotics: activate sphincter (PS) or block dilator (S)  Mydriatics: activate dilator (S) or block sphincter (PS)

Abnormal pupil • Congenital defects (e.g. coloboma, aniridia and polycoria, corectopia, congenital horners syndrom ) •Trauma : mydriasis or sphincter rupture D shaped pupil in irridodyalisis and surgical trauma. •Inflammatory: iridocyclitis miosis, Irregular narrow pupil, Festooned pupil (effect of mydriatics in presence of posterior synechiae). •Angle closure glaucoma: A fixed vertically oval middilated pupil in association with severe pain, a red eye, a cloudy cornea and systemic malaise suggests acute which warrants immediate referral.

Systemic : Diabetis narcotics(morphine, pethidine) cause miosis. mydriatics and miotics. Abnormal reflex

abnormalities of the Shape: Congenital abnormalities Aniridia - this is a bilateral condition arising from the abnormal neuroectodermal development secondary to genetic mutation. It is associated with glaucoma and a number of serious, systemic abnormalities.

Coloboma :

(corectopia, ectopia pupillae) Ectopic (Misplaced) Pupils: Isolated ectopic pupils may be inheritant the pupils may be displaced in any direction the pupils is frequently associated with ectopia lentis, congenital glaucoma, microcornea, ocular coloboma, and high myopia. Ectopic pupils also occur in some patients with albinism and some patients with Axenfield Rieger anomaly. acquired corectopia may occur in patients with severe midbrain damag, ICE syndrome , posterior polymorphous corneal dystrophy.

Polycoria and Pseudopolycoria: In true polycoria, the extra pupil or pupils are equipped with a sphincter muscle that contracts on exposure to light. This is an extremely rare congenital condition. This pseudopolycoria is passive constriction, distortion, or even occlusion of the accessory pupil when the true pupil is dilated (More commonly, pseudopolycoria occurs as an acquired disorder from direct iris trauma including surgery, photocoagulation, ischemia, or glaucoma or as part of a degenerative process such as the ICE syndrome

Irregular pupil in a case of iridocyclitis

Angle closure glaucoma

Pupil in diabetes Constricted Sluggishly reactive due to Glycogen infiltration of spincter Autonomic denervation Arteriosclerosis of radial iris vessels

Acquired structural abnormalities Pseudoexfoliation syndrome :

Abnormal reflex Unilateral light-near dissociation - afferent conduction defect, Adie pupil, herpes zoster ophthalmicus, aberrant regeneration of the third cranial nerve. Bilateral - neurosyphilis, diabetes, myotonic dystrophy, Parinaud dorsal midbrain syndrome.

Light reflex: Absolut afferent pupillary defect. RAPD ( relative afferent pupillary defect) • RAPD seen in optic nerve & retinal diseases with extensive retinal damage

Efferent Pupillary Defect DDx A B C D D

Efferent Pupillary Defect DDx Adie’s pupil Botulism CN III lesion Direct trauma Drugs

• Adie’s pupil( later ) • Botulism – Botulinum toxin binds irreversibly to presynaptic neuron. – Peripheral & cranial nerve Produces an exotoxin inhibiting ACh release

Occular symptoms of botulism Diplopia Blurred vision Photophobia Occular signs Ptosis Extraoccular palsies Markedly fixed & dilated pupils

CN III lesion Vascular lesion Aneurysm Neoplasm Trauma Inflammatory Infiltrative lesion Cavernous sinus lesion

Direct trauma Damage to the nerve endings Damage to the iris sphincter muscle

Drugs Anticholinergics Atropine, scopolamine, hyoscyamine Ipratropium bromide (nebulizer)

To differantiate: In afferent (sensory) lesions, the pupils are equal in size. Anisocoria (inequality of pupillary size) implies disease of the efferent (motor) nerve, iris or muscles of the pupil.

Adie’s Tonic Pupil Dilated pupil; poor light response; better near response Due to ciliary ganglion disease or short ciliary initially paralyzes sphincter pupillae and may paralyze ciliary muscle, causing failure of accommodation Gradually accommodation returns (more fibers from ciliary ganglion innervate near than light response) Pupil sphincter response returns more slowly, and remains sluggish to light and more responsive to near (accommodation) Usually unilateral Response tonically to dilute pilocarpine due to denervation hypersensitivity

Dynamic Anisocoria - Adie’s Tonic Pupil (OD) Adie’s Pupil - room light Poor direct response

Dynamic Anisocoria - Adie’s Tonic Pupil (OD) Poor consensual response Better near response

Dynamic Anisocoria - Adie’s Tonic Pupil (OS) Immediately after prolonged near fixation dilation lag (OS) Eventually left pupil fully redilates Hypersensitive response to pilocarpine (parasympathomimetic)

Parinaud syndrome • Bilateral mid-dilated pupils that react poorly to light but constrict normally with convergence (i.e., not tonic). Associated with eyelid retraction, supranuclear upgaze paralysis, and convergence retraction nystagmus. An MRI should be performed to rule out pinealoma and other midbrain pathology.

Argyll Robertson pupil • Causes • neurosyphilis, DM, encephalitis, MS and alcholism. • ch: • Asmall irregular pupil , anisocoria, lightnear dissociation: light reflex absent &near is normal, poor dilatation in dark and mydriatics

Raeder’s Syndrome • Unilateral headache (cluster) or facial pain in distribution of trigemial nerve • Ptosis • Miosis • Conjunctival hyperemia

Horner’s Syndrome (Oculosympathetic Paresis)

Congenital Horner’s Syndrome

Pharmacologic Evaluation

Cocaine test • Produces pupillary dilation by preventing reuptake of norepinephrine • Cocaine 10% (2 drops, 5 minutes apart) • In order to act it require functioning oculosympathatic pathway. • Dilate normal pupil only

Mechanism of action

Apraclonidine test • α2 agonist with significant α1 effect • Apraclonidine produces significant dilation of the affected pupil, but the normal pupil will fail to respond

Hydroxyamphetamine Localizing Test • Dilates the pupil only in presence of endogenous norepinephrine. • 2 drops of 1% hydroxyamphetamine 2 days after cocaine test.

• Indirect-acting receptor agonist – Forces norepinephrine from sympathetic nerve terminal • localization of Horner’s syndrome lesion – Mydriasis central or preganglionic – No mydriasis postganglionic

Requires postganglionic be intact

Adrinaline 1:1000 test In both eye: • In preganglionic lesion→ both pupil not dilate because adrinaline is destroyed by amine oxidase • In postganglionic lesion → Horner`s pupil will dilate because amine oxidase is absent.

Dilatation Lag Test Demonstrates impaired sympathetic response of the affected pupil with flash photography.series of 3 photographs were taken. • The first was in room light with added light in one eye from a penlight. • The second photograph was taken in darkness, 4 to 5 seconds after the lights were turned off. • the third, in darkness 10 to 12 seconds after the lights were extinguished. Horner’s pupil will lag behind in dilation, especially at 4-5 seconds

Dilatation Lag Test

Pourfour de Petit Syndrome This syndrome is the clinical opposite of Horner syndrome. It represents oculosympathetic overactivity unilateral mydriasis, lid retraction, apparent exophthalmos, and conjunctival blanching Seen after trauma, brachial plexus anesthetic block or other injury, and parotidectomy

Hutchinson’s pupil • Useful in assessment of head injuries • Stage1 : Ipsilateral pupil (on the side of head injury shows contraction due to irritation, Contralateral (normal) pupil – normal • Stage2 : Ipsilateral pupil shows dilatation due to paralysis , contralateral pupil constricts (irritation spreads to normal side)

Stage3 : Both pupils dilate. Stage of bilateral paralysis. To assess pupil repeatedly is important, therefore mydriatics should be avoided in case of head injuries

Conclusions

abnormally constricted pupil – Unilateral use of a miotic. – Iritis: Eye pain, redness, and anterior chamber cells and flare. – Horner syndrome:miosis ptosis anophthalmos. – Argyll Robertson pupil:acc reflex preserved. – Long-standing Adie pupil: The pupil is initially dilated, but over time may constrict. Hypersensitive to pilocarpine 0.125%. – Pontine hge.

Abnormally dilated pupil – Iris sphincter muscle damage from trauma: Torn pupillary margin or iris transillumination defects seen on slit-lamp examination. – Adie (tonic) pupil. – Third nerve palsy. – Unilateral exposure to a mydriatic. – Coma.

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