PUPIL IN HEALTH AND DISEASE

CHAIRPERSON : PROF.DR.M.S.KRISHNAMURTHYPRESENTER : DR. AMAR PATIL

NORMAL PUPILThe pupil is an opening located in the center of the IRIS that allows light to enter the retina.The size of the pupil determines the amount of light that enters the eye.The pupil size is controlled by the dilator and sphincter muscles of the iris.

Number Normally there is one pupil. More than one is called polycoria

Location Normally almost central (slightly nasal) . Eccentric pupil is called Correctopia.

Size Varies from 2.5mm to 4mm depending upon the illumination. Miotic pupils are less than 2mm. Mydriatic pupils are more than 7mm.

NORMAL PUPIL ABNORMAL PUPIL

May be variable in size but should be equal

Unequal

React to light Not reacting to light

Central Not central

Round Irregular

Dilated or Constricted

Functions of pupil•It regulates the amount of light entering the eye.•It improves the visual acuity because it prevents the irregular refraction by the periphery of the cornea and lens, and increases the depth of focus.•It allows the passage of aqueous humour from the posterior chamber to the anterior chamber.

Relevant Anatomy The IRIS contains 2 groups of smooth muscles :A circular group called sphincter pupillae.A radial group called dilator pupillae.

The Pupillary Reflexes There are essentially 3 reflexes to specifically test forLight-reflex testNear-reflex test Swinging flashlight test

Light Reflex test What it assesses – the integrity of the pupillary light reflex pathway.

How to perform – dim the ambient light and ask the patient to fixate on a distant target. Shine on the right eye from the right side and on the left eye from the left side ( do not stand in front of the patient as the pupils will accommodate to focus on you )

Normal Response – there should be a brisk, simultaneous, equal response of both pupils in response to light shone in one or the other eye.

Parasympathetic pathway First Order – Retina to Pretectal nucleus in the Brain Stem ( at the level of the superior colliculus) Second order – Pretectal nucleus to EWN ( Bilateral innervation ) Third order – EWN to Ciliary ganglion. Fourth order – Ciliary Ganglion to Sphincter pupillae ( via short ciliary nerves )

Why Consensual light reflex ?The light reflex is mediated by the retinal photoreceptors and subserved by four neurones.The SECOND INTERNUNCIAL connects each pre-tectal nucleus to both Edinger-Westphal nuclei, Thus a unilocular light stimulus evoked a bilateral and symmetrical pupillary constriction.

Sympathetic Pathway First Order – Posterior hypothalamus to Ciliospinal center of Budge (C8-T2) – Uncrossed in brain stem. Second Order – Ciliospinal center of budge to Superior Cervical Ganglion Third Order – Superior Cervical Ganglion to dilator pupillae muscle ( Close to ICA and joins V1 intracranially ) via nasociliary nerve and the long ciliary nerves.

Near-reflex test What it assesses – This assesses the miosis component of near fixation ( the other being accommodation – increased lens thickness and curvature, and convergence of eyes). How to perform it – In a normally lit room, instruct the patient to look at a distant target. Bring an object into the near point and observe the pupillary reflex when their fixation shifts to the near target. Normal response – There should be brisk constriction.

Accommodation reflex pathwayThe afferent stimulus is carried from retina via the optic nerve, tract and radiation to the calcarine cortex of the occipital lobeFrom here fibers pass to the frontal lobe and from here the corticobulbar fibers go to the III C.N Nucleus (nucleus of the medial rectus and the Edinger-Westphal nucleus) which results in accomodation reflex.

Swinging-flashlight test What it assesses – Compares direct and consensual responses of each eye (as opposed to seeing whether they are there or not)

How to perform – In a dim room light, the examiner notes the size of the pupils. The patient is asked to gaze into the distance, and the examiner swings the beam of a penlight back and forth from one pupil to the other, and observes the size of pupils and reaction in the eye that is lit.

Normal Response – Normally, each illuminated pupil promptly becomes constricted. The opposite pupil also constricts consensually.

Other pupillary reflexes CILIOSPINAL REFLEXThe ciliospinal reflex (pupillary-skin reflex) consists of dilation of the ipsilateral pupil in response to pain applied to the neck, face, and upper trunk. If the right side of the neck is subjected to a painful stimulus, the right pupil dilates (increases in size 1-2mm from baseline). This reflex is absent in Horner's syndrome and lesions involving the cervical sympathetic fibers.

DISORDERS OF THE PUPIL

ANISOCORIAAnisocoria is defined as a difference of 0.4 mm or more between the sizes of the pupils of the eyes.About 20% of normal people have a slight difference in pupil size which is known as physiological anisocoria. In this condition, the difference between pupils is usually less than 1 mm.

If the larger pupil is abnormal ( poor constriction ), the anisocoria is greatest in Bright illumination, as the normal pupil becomes small. Caused by disruption of Parasympathetic pupillary pathway.If the smaller pupil is abnormal ( poor dilatation ), the anisocoria is greatest in dark illumination, as the normal pupil becomes large. Caused by disruption of Sympathetic pupillary pathway.

MYDRIASISThis results from paralysis of the parasympathetic fibers, either at their origin from the pretectal nuclei and the EW nucleus in the midbrain, during the course with the III C.N or at the ciliary ganglion at the orbit.Most commonly such lesions are due to vascular accidents in the mid brain, tentorial herniation ( due to cerebral space occupying lesions) or aneurysms of the carotid artery

Other conditions commonly causing mydriasis are i. III C.N Palsy.ii. Adie’s Tonic Pupil.iii. Post traumatic iridoplegiaiv. Overdose – Glutethemide, Amphetamine, Cocainev. Poisoning – Belladona, Daturavi. Drugs – Anticholinergics like atropine,

homatropine, scopalamine. Sympathomimetics like epinephrine, nor-epinephrine, phenylephrine.

MIOSIS This indicates a lesion in the sympathetic pathway to the pupillary dilator Thus the lesion may be in the hypothalamus, brain stem, lateral aspect ( the spinal cord as far down as the

upper thoracic segments)

the sympathetic chain, the cervical sympathetic ganglion, the precarotid plexus the sympathetic fibers which run to the orbit

accompanying the ophthalmic division of the V Cranial Nerve

MIOSIS - CAUSESi. Horner’s Syndromeii. Argyll Robertson pupilsiii. Pontine tumours or hemorrhages. iv. Opiatesv. Organophosphorous or alcohol poisoning.vi. Pilocarpine dropsvii. Old Ageviii.Drugs – Cholinomimetics like pilocarpine, methacholine,

muscarine. Cholinesterase inhibitors like physostigmine and neostigmine.

Light-Near DissociationThe Pupillary reaction to light is normally equal to or greater than the reaction to near.Light near dissociation refers to a disparity between the light and near reactions. The most common form is a poor is a poor light response but a good near reposnse.The converse better reaction to light than to near, is rare.

Light-Near DissociationThe fibers mediating the pupillary light reflex enter the dorsal brainstem, but the near response fibers ascend to the EW nucleus from the ventral aspect.Pressure on the pupillary fibers in the region of the pretectum and posterior commisure impairs light reaction. However fibers mediating the near response, the EW nucleus, and the efferent pupil fibers are spared.

Argyll Robertson PupilAR Pupils are small (miosis), irregular in outline and have light near dissociation.They react poorly to light but very well to near reflex.AR Pupils are usually bilateral and symmetrical.Vision grossly intact.

Argyll Robertson PupilThe lesion lies in the periaqueductal region, pretectal area and rostral mid brain dorsal to the EW nuclei.AR Pupils are a classical eye finding in neurosyphilis.Also seen in Tabes Dorsalis, G.P.I ( Paralytic dementia ) and Aortic Regurgitation.

Reverse Argyll Robertson PupilVery rare.Pupils react to light but not to accommodation.Due to lesion in occipitotectal tract eg., encephalitis lethargica, Diphtheria.

Light-Near Dissociation - CausesNeurosyphilis Adie’s Pupil

Tabes Diabetica Aberrant regeneration of Cranial Nerve III

Lyme disease Sarcoidosis

Chronic Alcoholism Multiple Sclerosis

Chiasmal lesions ( Tabes Pituitaria ) Wernicke’s Encephalopathy

Myotonic Muscular dystrophy Amyloidosis

Afferent pupillary defect1. Absolute Afferent Pupillary defect ( Amaurotic

pupil ) is caused by a complete optic nerve lesion.2. Relative Afferent Pupillary defect ( Marcus Gunn

pupil ) is caused by an incomplete optic nerve lesion.

Absolute Afferent Pupillary defect

Caused by complete optic nerve lesion. Characterized by –

a. Involved eye is completely blind i.e., no light perception.b. Both pupils equal in size.c. When affected eye is stimulated by light neither pupil reacts.d. When the normal eye is stimulated both pupils react normally.e. Near reflex is normal in both eyes

Relative Afferent Pupillary defect A relative pupillary defect ( Marcus Gunn pupil ) is caused by an incomplete optic nerve lesion or severe retinal disease.The clinical features are similar to those of an amaurotic pupil but more subtle.

A right relative defect is Characterized by – a. When the normal left eye is stimulated both pupils

constrict.b. When the light is swung to the diseased right eye, both

pupils dilate instead of constricting ( Pupillary escape phenomenon ).

The paradoxical dilatation of the pupils in response to light occurs because the dilatation produced by withdrawing the light from the normal eye outweighs the constriction produced by stimulating the abnormal eye.

A Marcus Gunn pupil is seen I. In optic neuritis. II. It is also common in retrobulbar optic neuritis

due to multiple sclerosis but only for 3–4 weeks, until the visual acuity begins to improve in 1–2weeks and may return to normal.

Other causes of Optic NeuritisInfection (e.g. syphilis, Lyme disease, herpes zoster), Autoimmune disorders (e.g. lupus, neurosarcoidosis, neuromyelitis optica), Inflammatory bowel disease, Drug induced (e.g. chloramphenicol, ethambutol, Isoniazid, streptomycin, quinine, penicillamine, Aminosalicylic acid, phenothiazine, phenylbutazone), Vitamin B12 deficiency Diabetes Mellitus

Oculomotor - III Cranial Nerve PalsyOculomotor nerve palsy or third nerve palsy is an eye condition resulting from damage to the third cranial nerve or a branch.A complete Oculomotor nerve palsy will result in a characteristic down and out position in the affected eye.

The eye will be displaced outward and displaced downward; outward because the lateral rectus (innervated by the sixth cranial nerve) maintains muscle tone in comparison to the paralyzed medial rectus. The eye will be displaced downward, because the superior oblique (innervated by the fourth cranial or trochlear nerve), is unantagonized by the paralyzed superior rectus, inferior rectus and inferior oblique. The affected individual will also have a ptosis, or drooping of the eyelid, and mydriasis (pupil dilation).

Since the pupillary parasympathetics occupy a position on the dorsomedial periphery of the nerve as it exits the brain stem, compressive lesions such as aneurysms generally affect the pupil prominently.Ischemic lesions tend to affect the interior of the nerve and spare the pupil, as in diabetic third nerve palsies, because the periphery of the nerve has a better vascular supply.

Barton’s pupil ruleComplete pupil sparing with otherwise isolated and complete palsy of CN III is never due to an aneurysm.

When the ocular sympathetics are involved along with CN III the pupil may be midposition because the sympathetic denervation prevents the pupil from dilating fully.This occurs most commonly in Cavernous Sinus lesions when there is compression of both CN III and pre-carotid sympathetics, leaving the pupil mid-size but unreactive.This should not be mistaken for pupil sparing CN III palsies sometimes complicated by aberrant reinnervation.

Oculosympathetic palsy ( HORNER SYNDROME )

Causes of HORNER SYNDROME CENTRAL (first-order neurons) PREGANGLIONIC(second-order

neurons)POSTGANGLIONIC ( third-order neurons)

Brain stem disease ( tumour, vascular, demyelination )

Pancoast tumour Cluster headcahes ( migrainous, neuralgia)

Syringomyelia Carotid and aortic aneurysm and dissection

ICA dissection

Lateral medullary syndrome Neck lesions ( glands, trauma, postsurgical)

Nasopharyngeal tumour

Spinal cord tumour Otitis Media

Diabetic autonomic neuropathy

Cavernous sinus mass

SIGNSi. Partial Ptosis ii. Miosisiii. Normal pupillary reactions to light and neariv. Hypochromic Heterochromia ( may be seen if congenital )v. Slight elevation of inferior eyelid as a result of weakness of

inferior tarsal musclevi. Reduced ipsilateral sweating, but only if lesion is below the

superior cervical ganglion.

Confirmation of Horner’s syndrome is with instillation of a drop of 4% cocaine

In physiological anisocoria, this results in dilatation whereas it doesn’t where there is a horner’s syndrome. For further localization – 1% hydroxyamphetamine is added ( 48 hrs after coccaine test )

Pupillary dilatation suggests a central or preganglionic Horner’s syndrome whereas if dilatation does not occur the lesion is likely to be postganglionic.

Pourfour de Petit SyndromeThis 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.

Adie’s Tonic PupilThis describes a unilateral ( 80% of the cases ) mydriatic pupil in otherwise healthy patients ( typically young adults, especially women ) Cause – Denervation of the postganglionic supply to the sphincter pupillae and the ciliary muscle, which may follow a viral illness (eg., herpes zoster).

Adie’s tonic pupil - SignsLarge and regular pupil.There is a sluggish reaction to light but normal near reflex.Re-dilatation after the near response is slow.Over months to years the pupil diminishes in size to eventually become miotic ( little old Adie’)Associations – In some cases there are diminished deep tendon reflexes ( Holmes-Adie syndrome) +/- autonomic dysfunction.

Adie’s tonic pupil – DiagnosisThe diagnosis is confirmed by the pupil’s hypersensitivity to weak miotic drops (0.05 to 0.125% pilocarpine ) which causes the abnormal pupil to contract vigorously and the normal pupil minimally.It’s a benign condition : With time the accommodative response improves while the tonicity of the light response gets worse. There is no treatment and patient reassurance is important.

Hemianopic pupil ( Wernicke’s pupil )Seen in optic tract lesions with hemianopia.Stimulating the blind half of retina pupil shows no reaction.

Stimulating seeing half of retina pupil shows reaction.

Difficult to elicit – due to scattering & diffusion of light.

Use a narrow streak of light.

Parinaud’s syndromeAlso called Dorsal midbrain syndrome. Its uncommon.The pupils are mid-dilated due to damage to the pretectal pupilloconstrictor nuclei.It involves vertical gaze palsy associated with pupils that accommodate but do not react ( light near dissociation ).The causes of Parinaud syndrome include brain tumors (pinealomas), multiple sclerosis and brainstem infarction.

Pupils during sleep Normally, there is a tonic inhibitory input from the cerebral cortex to the Edinger - Westphal nucleus, and it is a diminution of this input that results in pupillary constriction during sleep.

Pupil in DiabetesConstrictedSluggishly reactive due to •Glycogen infiltration of spinchter.•Autonomic denervation.•Arteriosclerosis of radial iris vessels.

Hutchinson’s pupilHutchinson's pupil is a clinical sign in which the pupil on the side of an intracranial mass lesion is dilated and unreactive to light, due to compression of the oculomotor nerve on that side. These can be due to concussion injury to the brain and is associated with subdural haemorrhage and unconsciousness.

The parasympathetic fibers to the pupil are responsible for pupillary constriction. The fibers pass through the periphery of the oculomotor nerve, and hence are the first to be affected in case of compression of the nerve.

Hutchinson’s pupil - StagesIn Stage 1, the parasympathetic fibers on the side of injury are irritated, leading to constriction of pupil on that side. In stage 2, the parasympathetic fibers on the side of injury are paralysed, leading to dilatation of pupil. The fibers on the opposite oculomotor nerve are irritated, leading to constriction on opposite side. In stage 3, the parasympathetic fibers on both sides are paralysed - leading to bilateral pupillary dilatation. Pupils become fixed. This indicates grave prognosis.

Pupils in the Emergency Room1. Head injury / In an unconscious patient Normally reacting equal pupils – Reassuring sign,

No intracranial catastrophe. To look for metabolic causes.

Unequal pupils – Single most important physical sign indicating that a herniated temporal lobe is stretching the III C.N on that side and prompt treatment is necessary.

Bilateral dilated pupils – The final stage of progressive tentorial herniation. The chances of patient recovering at this stage are very poor.

Bilateral pinpoint pupils - Indicates a massive intrapontine hemmorhage. Opiates produce similar pupillary abnormalities but cause depressed reflexes.

References1. De Jong’s The Neurological Examination by William W. Campbell 7th Edition.

2. Harrison’s Internal Medicine Volume 1 – 19 th Edition.

3. Kanski’s Clinical Ophthalmology 8th Edition.

4. Neurological Differential Diagnosis by John Patten.

5. Neuro-ophthalmology by Joel.S.Glaser 3rd Edition.

6. Bickerstaff’s Neurological Examination in Clinical Practice 7th Adapted Edition

7. Dr. Aruj Khurana. "Concussion injuries to the brain". Comprehensive Ophthalmology (fourth ed.) (New Age International (P)): 311.

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