This document discusses the pupil in health and disease. It begins by describing the normal anatomy and function of the pupil, including its size, location, shape, and role in regulating light entry. It then covers various pupil reflexes and abnormalities such as anisocoria, mydriasis, miosis, light-near dissociation, Argyll Robertson pupils, and disorders of the third cranial nerve and sympathetic pathway. Causes, signs, and diagnostic tests for various pupil abnormalities are provided.

1. PUPIL IN HEALTH AND
DISEASE
CHAIRPERSON : PROF.DR.M.S.KRISHNAMURTHY
PRESENTER : DR. AMAR PATIL

2. NORMAL PUPIL
The 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.

4. Number
Normally there is one pupil.
More than one is called polycoria
Location
Normally almost central (slightly nasal) .
Eccentric pupil is called Correctopia.

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

6. 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

7. 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.

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

10. The Pupillary Reflexes
There are essentially 3 reflexes to specifically test for
Light-reflex test
Near-reflex test
Swinging flashlight test

11. 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.

12. 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 )

14. 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.

15. 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.

18. 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.

20. Accommodation reflex pathway
The afferent stimulus is carried from retina via the
optic nerve, tract and radiation to the calcarine
cortex of the occipital lobe
From 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.

22. 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.

24. Other pupillary reflexes
CILIOSPINAL REFLEX
The 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.

25. DISORDERS OF THE PUPIL

26. ANISOCORIA
Anisocoria 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.

27. 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.

28. MYDRIASIS
This 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

29. Other conditions commonly causing mydriasis are
i. III C.N Palsy.
ii. Adie’s Tonic Pupil.
iii. Post traumatic iridoplegia
iv. Overdose – Glutethemide, Amphetamine, Cocaine
v. Poisoning – Belladona, Datura
vi. Drugs – Anticholinergics like atropine,
homatropine, scopalamine. Sympathomimetics like
epinephrine, nor-epinephrine, phenylephrine.

30. 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)

31.  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

32. MIOSIS - CAUSES
i. Horner’s Syndrome
ii. Argyll Robertson pupils
iii. Pontine tumours or hemorrhages.
iv. Opiates
v. Organophosphorous or alcohol poisoning.
vi. Pilocarpine drops
vii. Old Age
viii.Drugs – Cholinomimetics like pilocarpine, methacholine,
muscarine. Cholinesterase inhibitors like physostigmine
and neostigmine.

33. Light-Near Dissociation
The 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.

34. Light-Near Dissociation
The 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.

35. Argyll Robertson Pupil
AR 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.

36. Argyll Robertson Pupil
The 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.

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

39. Light-Near Dissociation - Causes
Neurosyphilis 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

40. Afferent pupillary defect
1. 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.

41. 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

42. 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.

43. 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.

44. 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.

45. Other causes of Optic Neuritis
Infection (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

46. Oculomotor - III Cranial Nerve Palsy
Oculomotor 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.

47. 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).

48. 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.

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

50. 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.

51. 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

52. SIGNS
i. Partial Ptosis
ii. Miosis
iii. Normal pupillary reactions to light and near
iv. Hypochromic Heterochromia ( may be seen if congenital )
v. Slight elevation of inferior eyelid as a result of weakness of
inferior tarsal muscle
vi. Reduced ipsilateral sweating, but only if lesion is below the
superior cervical ganglion.

54.  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.

55. 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.

56. Adie’s Tonic Pupil
This 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).

57. Adie’s tonic pupil - Signs
Large 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.

58. Adie’s tonic pupil – Diagnosis
The 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.

60. 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.

61. Parinaud’s syndrome
Also 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.

62. 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.

63. Pupil in Diabetes
Constricted
Sluggishly reactive due to
•Glycogen infiltration of spinchter.
•Autonomic denervation.
•Arteriosclerosis of radial iris vessels.

64. Hutchinson’s pupil
Hutchinson'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.

65. 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.

66. Hutchinson’s pupil - Stages
In 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.

67. Pupils in the Emergency Room
1. 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.

68.  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.

69. References
1. 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.

70. THANK YOU