examination of the pupil is important in neurology and ophthalmology

1. Dr. K. Vasantha M.S., F.R.C.S.,
Director RIO Chennai Rtd

2.  Very often we just shine the torch, see whether the pupil
reacts and go on to the next test. This type of cursory
examination will cause troubles later as we cannot check
the reaction again after dilating the pupil and seeing the
fundus.
 Many small abnormalities and sometimes even major
ones may be missed

3.  To control the quantity of light entering the retina
 To minimize aberrations caused by the rays of light
entering through the periphery of the lens and cornea
 To increase the depth perception

4.  Caused by contraction of the sphincter muscle. This
muscle circles the pupil in a dove tail manner. Hence
even if the iris is cut up to the pupil the rest of the fibers
can still react and constrict the pupil
 Nerve supply - parasympathetic

5.  Miosis to light gives us an idea about integrity of both
afferent and efferent fibers
 Damage to afferent fibers from retina, optic nerve, optic
tract will affect this reflex and vision
 Response to low intensity light is of low amplitude and is
by rods
 In light adapted state the cones come in to play and there
is a strong contraction

6.  The gamma ganglion cells responsible for light reflex is
more in the central retina
 Pupillary constriction has supranuclear in put from the
pretectal nucleus
 For accommodation the center is in the cortex from
where it descends down to the rostral mid brain

7.  When the sphincter muscle relaxes pupil will dilate.
 The dilator muscle is more peripheral and radially
arranged and causes further dilatation
 Nerve supply- sympathetic
 Both these muscles arise from the neurectoderm

8.  The pupil dilates because of supranuclear inhibition of
the Edinger Westphal nucleus
 This inhibition is not present during sleep, anesthesia
and when under narcotics -> miosis
 Reduction in light also reduces the in put to EW nucleus,
relaxes the sphincter -> dilatation
 Besides the action by nerves, the catecholamines can
travel through blood in a bolus like when you are
frightened, and dilate the pupil

9.  Transient fluctuations in pupillary reaction is called
“hippus”.
 This is normal
 In children and old people the pupil will be miotic
 During sleep the pupil will become miotic – Westphal
Piltz reflex

10.  Photoreceptors -> ganglion cells -> fibers pass through
the optic nerve -> optic tract -> emerges before reaching
the lateral geniculate body -> passes through pretectal
nuclei -> inter neurons to Edinger Westphal Nucleus on
both sides

11.  EW nuclei -> travels with the III nerve
 The fibers are present on the external side. So any
compression or infiltration may affect the pupillary
reaction first
 -> in the orbit -> inferior division of III nerve -> synapse in
the ciliary ganglion -> fibers are close to the nerve fibers
for the inferior oblique
 Short ciliary nerves enter the sclera -> sphincter muscle
of the iris

12.  Hypothalamus (first interneuron) -> synapse in the spinal
cord @ C8 – T2 9 cilio spinal center of Budge)
 II order (preganglionic) leaves the cord, travels close to
the apex of the lung and lower part of brachial plexus.
Then goes upwards with the internal carotid artery

13.  Synapse in the superior cervical ganglion
 III order fibers goes in to the cavernous sinus -> close to
VI nerve and then travels with naso ciliary nerve -> long
ciliary nerve to dilator muscle in the iris
 Hence when there is VI nerve palsy the pupil must be
checked diligently

14.  Asymmetric sizes i.e. anisocoria can be normal. But here
the difference will be small
 Anisocoria >in bright light - the larger pupil is likely to
have abnormal parasympathetic connection
 Anisocoria >in dark – smaller pupil is likely to have
sympathetic dysfunction

15.  Corectopia
 Aniridia
 Coloboma
 Anterior chamber cleavage abnormalities
 D shaped pupil following blunt injury
 Multiple pupils. In this each pupil will act as they all have
separate constrictor muscles. If the opening is due to
injury, it will not act

16.  This is an important test as it gives an idea about
whether the defective vision is due to optic nerve
problem or not.
 In case the fundus is normal and the vision is affected
due to retro bulbar neuritis this test will clinch the
diagnosis.
 While doing this test light must be shown from the front
and care must be taken to throw equal amount of light on
each eye while testing

17.  Throw the light on the affected eye first. The pupil will
not constrict or will constrict and dilate again
 Then show the light on the other eye. The pupil which
was not constricted due to the absence of consensual
reaction, will now constrict.
 Go back to the affected eye. Now the pupil which was
constricted due to consensual reaction will dilate instead
of further constricting.
 Since you go back and forth it is also called swinging
flash light test

18. Subjective gradation
 1+ - initial constriction and early redilatation
 2+ - no initial constriction and then dilatation
 3+ - immediate dilatation
 4+ - amaurotic pupil. Non reactive even to brightest
stimuli

19.  Neutral density filters graded in log units can be used.
The density of the filters placed in front of the good eye
is increased till the reaction is equal
 Computerized pupillography also can be done
 Patient also can be asked to compare the brightness
between the two eyes

20.  If complete hemianopia is present, a relative afferent
pupillary defect may be present in the eye contra lateral
to the lesion in the optical tract. This is because there are
slightly more no of nerve fibers in the nasal side
 To detect the loss of reflex when light is shown on the
affected field special lighting system is needed to avoid
diffuse light

21.  When optic tract is affected the pupil contra lateral to the
lesion (ipsilateral to the field loss) may be larger than the
other pupil. Rare
 ? Due to injury to the hypothalamus causing constriction
of the pupil on the same side as the lesion

22.  Seen in uncal herniation due irritation of the nerve
against the tentorium cerebelli, kinking of the nerve over
the clivus or due to compression of oculomotor nucleus
 In the first stage pupil on one side will constrict
 When there is further herniation this pupil will dilate due
to compression and the opposite pupil will constrict
 On further herniation both pupils will be dilated

23.  Miotic, slightly irregular
 Both direct and consensual reaction lost
 Dilates poorly in the dark
 Brisk near reflex
 Cause: syphilis, diabetes
 Damage to fibers in the midbrain between pretectal
nucleus and EW nucleus or at ciliary ganglion

24.  It is a tonic pupil
 More in women
 Usually unilateral
 Symptoms: photophobia due to poor constriction
 Difficulty in reading
 Difficulty in refixing to distance after reading

25.  Slightly larger pupil
 Constricts and then dilates very slowly
 In early cases near response also may be slow
 When seen with slit lamp, vermiform movements will be
seen due to sectoral immobility

26.  ? Due to damage to ciliary ganglion or the post
ganglionic short ciliary nerves
 As more fibers supply ciliary muscle response for
accommodation - miosis for near is preserved
 After injury misdirection can cause fibers for
accommodation, supplying the sphincter -> excess
pupillary constriction during accommodation
 This will appear as light near dissociation

27.  Local – viral esp. varicella,
 Trauma,
 Sarcoidosis,
 Ischemia – vasculitis or giant cell arteritis

28.  Pan retinal photo coagulation can cause damage to
ciliary nerves and cause, irregular poorly dilating pupil
 Autonomic neuropathy
 Neovascularisation of iris
 Iris ischemia
 Ross syndrome- tonic pupil, hyper reflexia and
segmental anhidrosis

29.  Instillation of 0.125% pilocarpine will cause constriction
of pupil. (This is just a test)
 Syphilis has to be ruled out
 If elderly ESR has to be done and giant cell arteritis has
to be ruled out

30.  Here along with tonic pupil there will be absence of deep
tendon reflexes
 This is due to involvement of ciliary and dorsal root
ganglia

31.  If the pupillary fibers are not affected it is usually
considered to be due to diabetic palsy as the pupillary
fibers supplied by the pial blood vessels may escape
ischemia
 Otherwise the pupil will be slightly larger than the other
eye, and will not constrict when light is shown

32.  Lesion in the dorsal mid brain
 The axons of the ganglion cells before entering the
pretectal region are affected
 Both pupils will be slightly dilated. May be asymmetric
 Light near dissociation
 Accommodation may be retained due to intact
supranuclear connection

33.  Up gaze paresis and convergence retraction
 Lid retraction – Collier’s sign
 Pseudo abducens palsy
 May be associated with third nerve palsy and inter
nuclear ophthalmoplegia
 Pineal region tumors, hydrocephalus

34.  Unilateral miosis
 Both upper and lower lid mild ptosis
 Anhidrosis
 Anisocoria which increases in the dark
 Dilatation in the miotic pupil
 Constriction normal for both near and distance
 Mild congestion of conjunctiva

35.  Tumors, infarction in the region of hypothalamus –
associated with contra lateral hemi paresis, ataxia
 Lesion in the dorsal midbrain – IV nerve palsy
 Wallenberg syndrome – infarction in lateral medullary or
posterior inferior cerebellar artery – besides nystagmus
defective corneal sensation and lateral rectus palsy may
be there

36.  Spinal cord – syringomyelia, trauma to spinal cord near
C8 – T2, myelitis, tumors, infarction, multiple sclerosis
 In these disorders in the first order neuron anhidrosis
may be seen on whole side of the body
 II order neuron- tumors of lung or mediastinum,
pancoast syndrome, injury to brachial plexus, surgery in
this region

37.  Raeder’s para trigeminal syndrome – Horner and facial
pain
 Carotid artery dissection
 Vascular headache
 Tonsillectomy – superior cervical ganglion and internal
carotid are just behind the tonsils
 Ischemia to cervical ganglion due to atherosclerosis or
giant cell arteritis

38.  In these lesions other oculomotor nerves and fifth cranial
nerve will also be affected
 Since III nerve is affected the pupil will be constricted
 But in the dark the affected pupil will become further
smaller

39.  Autonomic neuropathy e.g. diabetes
 Amyloidosis
 Middle ear infection
 In children- neuroblastoma of the cervical ganglion, birth
injury. The iris will be light colored as the iris
melanocytes need sympathetic in put for development

40.  Cocaine blocks re uptake of norepinephrine. So in all
three orders the pupil will not dilate like the normal pupil.
 So you can confirm but not localize the lesion
 Apraclonidine alpha receptor agonist even with 0.5% will
dilate affected pupil due denervation super sensitivity.
This drug is now freely available and is used now to
confirm Horner’s

41.  Hydroxy amphetamine enhances the release of
norepinephrine from III order neuron. So if this neuron is
affected the pupil will not dilate. But in delayed cases the
neurons will be destroyed. So it will not act. Anyway the
drug is not available now

42.  Drugs – miotic drops, opium, barbiturate poisoning
 Miosis on abduction can be congenital due to connection
between VI nerve and ciliary ganglion
 Paradoxic pupillary constriction in the dark can occur
due to achromatopsia and congenital stationary night
blindness

43.  Mydriatics, tricyclic antidepressants, botulism
 Migraine can cause mydriasis
 Tournay’s pupillary phenomenon – on lateral gaze the
pupil of the affected eye appears larger either due to
dilation or due to constriction of the other pupil.
 This can be normal, or due anomalous connection
between EW nucleus and the nucleus to medial rectus

44.  Oculo sympathetic spasm can be caused by infarction or
syringomyelia
 Idiopathic alternating mydriasis – within a day the pupil
will dilate and constrict many times
 Tadpole shaped pupil due to segmental pupillary
dilatation – Horner’s tonic pupil or in migraine