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

Range of pupil diameters

Day light: 2.5 - 4.0 mm

Extremes: 1.3 - 10 mm

Anisocoria - unequal diameters.

The Pupil - Characteristics

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)

Pupil Responses

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 mid-dilated 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

Congenital abnormalitiesAniridia - 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.

abnormalities of the Shape:

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

ConstrictedSluggishly reactive due to

Glycogen infiltration of spincterAutonomic denervationArteriosclerosis of radial iris vessels

Pupil in diabetes

Acquired structural abnormalities

Pseudoexfoliation syndrome :

Abnormal reflexUnilateral 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

ABCDD

Efferent Pupillary Defect DDx

Adie’s pupilBotulismCN III lesionDirect traumaDrugs

• Adie’s pupil( later )

• Botulism

– Botulinum toxin binds irreversibly to presynaptic neuron.

– Peripheral & cranial nerve Produces an exotoxin inhibiting ACh release

Occular signsPtosisExtraoccular palsiesMarkedly fixed & dilated pupils

Occular symptoms of botulismDiplopiaBlurred visionPhotophobia

CN III lesionVascular lesionAneurysmNeoplasmTrauma InflammatoryInfiltrative lesionCavernous sinus lesion

Direct traumaDamage to the nerve endingsDamage to the iris sphincter muscle

DrugsAnticholinergics

Atropine, scopolamine, hyoscyamineIpratropium 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 PupilDilated 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, light-near 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 TestDemonstrates 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 SyndromeThis syndrome is the clinical opposite of Horner syndrome. It represents oculosympathetic overactivity unilateral mydriasis, lid retraction, apparent exophthalmos, and conjunctival blanchingSeen 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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