Pupil

Dr Mohamed Alzein

Ass Prof @ Sebha Medical School

Sebha University, Sebha Libya

Normal pupilVaries with:

• Age,

• Person to person

• emotional state

• Level of alertness

• Degree of

accommodation

• Ambient room light.

Normal diameter: 3-4

mm.

• small (infants, &

elderlies).

• large (childhood &

middle-aged).

• Balance between

sphincter & dilator.

• Supranuclear control

(frontal & occipital).

Normal pupil• Hippus: responses to

respiration.

• Physiological (essential) anisocoria: 20-40% of GP.

• Mydriatics & cycloplegics work more on blue eyes > brown.

• Constriction: activation of circular sphincter pupillae (parasympathetic).

• Dilatation: contraction of the radiating dilator pupillae (sympathetic).

• Near response:Convergence, ↑ Accommodation, Miosis

Pupillary Light

reflex pathways

• Light reflex: Afferent arc: retina ON 20% OC (axons from nasal retina cross, axons from temporal retina remain uncross) OTbrachium of superior colliculus before LGN pretectal nuclei (50% IL & 50% CL via posterior commisure) 1st order neuron Edinger Westphal nucleus –pupiloconstrictor nucleus – 2nd order neuron.

Pupillary Light

reflex pathways

• Efferent arc: join with

somatic motor IIICN

fibers in brainstem on

its medial side-

preganglionic

ciliary ganglion

ciliary nerves –post-

ganglionic sph

pupillae.

Sympathetic nervous system

• Hypothalamus

ciliospinal center of

Budge in C8

sympathetic chain

superior cervical

(stellate) ganglion

sympathetic plexus of

ICA ophthalmic

artery ciliary

ganglion ciliary

nerves dilator

pupillae.

Near Response pathway

• Retina occipital cortex occipito-

bulbar pathway modify EOM

EWN III CN.

• Anisocoria: Physio or Patho (efferent

defect or local iris pathology).

• APD: Swinging flashlight test.

Miosis• Bright illumination

• Sleep

• Old age,

• Forced lid closure,

• Iritis,

• Pontine lesion,

• sympathetic chain lesion,

• Miotics (sympatholytics, parasympathomimetics

• Narcotics X pethidine.

Mydriasis

• Poor illumination

• Emotional stimuli

• Pain

• Mydriatics (sympathomimetics, & parasympatholytics)

• III CN disturbances ( ICP with tentorial coning)

• Trauma

• Toxic

• Infective conditions-botulism & diphtheria.

Pupillary Light reflex

Pupillary Light reflex- RAPD

Afferent Pupillary Defect

• RAPD:

Unilateral ↓Va sine RAPD:

• Refractive error

• Cloudy media

• Amblyopia

• Hysteria

• Malingering

• Macular lesion

• Chiasmatic lesion.

RAPD sine ↓Va:

• Lesion of brachium of superior colliculus (thalamic hg).

Amaurotic pupillary defect:

• in severe unilat retinal or optic nerve dz…..

Pupillary Light reflex- APD

Pupillary reflexes

Pupillary Light-Near Dissociation

• Light stronger > Near response as miotic, the reverse is known as light-Near Dissociation

• Causes: APD, CG & MB lesions, CNS syphilis, DM, chr alcoholism, encephalitis, MS, CNS deg. dz, MB tumors & infarcts, Lesion at periaqueductal gray matter of MB.

Argyl-Robertson Pupil (ARP)

• C/F: Pupil size < 3 mm (miotic), light reaction absent, accommodation reaction present (ARP), bilateral, irregular eccentric & dilate poorly with mydriatics-iris atrophy,

• Incomplete: slow response to light

• unilateral

• Causes: CNS syphilis + tabes dorsalis /general paresis, DM, chr alcoholism, encephalitis, MS, CNS deg. dz, MB tumors. Lesion at periaqueductal gray matter of MB.

Tonic pupil• C/F: L – N D, slow contraction of sphincter

to near stimulation –abnormal constrictor

mechanism, segmental iris constriction

Vermiform movements of edge.

• Acute stage : pupillary dilatation.

• Adie’s syndrome : Tonic pupil with absent

deep tendon reflexes.

Tonic pupil

• Damage to ciliary ganglion or short ciliary nerves (30 nn for Near response , 1 n for light reflex) by trauma or inflame… 0.1% Pilo test constriction (denervation hypersensitivity), if normal it is not affected.

• Coccaine drops diltation. Dilates slowly in dark & promptly to mydriatcs. young girls.

• Bilateral tonic pupils autonomic neuropathy.

Horner’s syndrome

Lesions of the sympathetic pathway:

• Central (post hypothalamus Br stem

C8-T2),

• Preganglionic (SC SCG) &

• Post-ganglionic SCG Carotid plexus Va

orbit) Muller’s muscle & Iris dilator.

Horner’s syndrome

C/F:

• Meiosis

• Ptosis

• Anhydrosis: absence of

facial & nuchal sweating

IL

• Heterochromia irides

(cong. Melanocyte

immaturation bluer

iris).

Horner’s syndrome

• Etiology;

• Central:

Brainstem infarct (Stroke)

Lateral medullary infarction (Wallenburg Syndrome)

Syringomyelia

Cervical cord tumor

Tabes dorsalis

Lyme dz

Vertebral artery dissection

Horner’s syndrome

• Preganglionic:

Cervical rib

Cervical vertebral #

Apical pulmonary lesion eg br Ca (Pancoast syndrome)

Brachial plexus injury.

Cervical spine abn

Neuroblastoma

Horner’s syndrome

• Postganglionic:

Dissecting aneurysm of

carotid or subclavian

a.

Carotid a injury high in

the neck

Cluster headaches

Pharmacology

Parasympathomimetics (miotics):

• Direct: Pilocarpine, Carbachol,

Acetylcholine.

• Indirect: Eserine, Edrophonium,

Echothiophate, Isofluorophate.

Sympatholytics (Miotics):

• Guanethidine, Dibenzyline, Tolazoline.

Pharmacology

Parasympatholytics (mydriatics):

• Direct: Atropine, Homatropine,

Scopolamine, Cyclopentolate,

Tropicamide.

Sympathomimetics (mydriatics):

• Direct : Epinephrine, Phenylephrine

• Indirect : Epinephrine, Cocaine.

• Some of the material in this presentation is

from the following sources:

• General ophthalmology by Vaughan &

Asbury.

• Clinical ophthalmology by J Kanski.

• Illustrated ophthalmology by Dean Hart.

• Internet.