Pupil Evaluation
Walter Huang, OD
Yuanpei University
Department of Optometry
Pupil
A black circular opening in the center of
the iris
It is surrounded by the pupillary margin of
the iris
Pupil
Purpose

To control the amount of light entering the eye
Normal Pupils
They are round in shape and relatively
equal in size
Their size vary from 1 to 8mm in diameter



Normal pupils range from 3 to 5mm in
ambient light conditions
Miotic pupils are less than 3mm
Mydriatic pupils are greater than 7mm
Pupil Size
Determined by




Age
Level of retinal illumination
Emotional factors (i.e., pain, pleasure, fear)
Amount of accommodation and/or
convergence (near reflex)
Pupil Contraction and Dilation
Controlled by two muscles of the iris

Sphincter muscle (pupil constriction)
Innervated by the parasympathetic nervous system

Dilator muscle (pupil dilation)
Innervated by the sympathetic nervous system
Muscles of the Iris and Pupil
Sphincter Muscle
The pupil size is mainly determined by the
contraction or relaxation of the sphincter
muscle
The sphincter muscle responds to signals
coming from the short ciliary nerve and
constricts the pupil
It is innervated by parasympathetic fibers
Dilator Muscle
The pupil size is secondarily determined
by the contraction or relaxation of the
dilator muscle
The dilator muscle responds to signals
coming from the long ciliary nerve and
dilates the pupil
It is innervated by sympathetic fibers
Nerve Pathway
Afferent pathway

Afferent nerve or input nerve
Nerve that carries sensory information towards the
central nervous system (i.e., brain and spinal cord)

Sensory pathway for pupil constriction
Nerve Pathway
Efferent pathway

Efferent nerve or output nerve
Nerve that carries impulses away from the central
nervous system (i.e., brain and spinal cord)

Parasympathetic and sympathetic pathways
for pupil constriction and dilation
Afferent Pathway of the Pupil
Light Reflex
Sensory pathway for pupil constriction
Axons from retinal ganglion cells (input)
↓
Optic nerve → Optic chiasm → Optic tract
↙
Edinger-Westphal ← Pretectal nucleus
nucleus
The Pathway of the Pupillary
Reaction to Light
Efferent Pathway of the Pupil
Light Reflex
Parasympathetic pathway for pupil
constriction
EW nucleus (output) → Cranial nerve III
Accommodation fibers ↗
↓ ↓
Ciliary body
Ciliary ganglion
↖
↓ ↓
Iris sphincter muscle ← Short ciliary nerve
Direct and Consensual
Response
The signal is passed to both sides of the
midbrain so that light information given to
one eye is passed on to both pupils
equally
Direct Response
Direct light reflex

The constriction of the ipsilateral pupil to the
light stimulus
Consensual Response
Consensual light reflex

The constriction of the contralateral pupil to
the light stimulus
Total Blindness
Total blindness due to bilateral cortical
lesion does not affect the light reflex
Total Blindness
Total blindness in one eye due to retinal or
optic nerve problem


Shine light in normal eye – have direct
response but no consensual response (similar
to shine light in bad eye)
Shine light in blind eye – no direct response
but have consensual response (similar to
shine light in good eye)
Efferent Pathway of the Pupil
Light Reflex
Sympathetic pathway for pupil dilation
Hypothalamus → Spinal cord
↘
Superior cervical ganglion
↙
Cranial nerve V → Eyelid muscles
↓
Long ciliary nerve → Dilator muscle
Anatomy of Sympathetic
Pathway
Near Reflex
Accommodation, convergence, and pupil
constriction (miosis) occur at the same
time
Artificially induced convergence causes
accommodation and miosis
Artificially induced accommodation causes
convergence and miosis
Near Reflex
Miosis is the weakest of the three
responses so that it cannot induce
accommodation and convergence
Some accommodation fibers innervate the
pupil
The convergence pathway is located close
to the Edinger-Westphal nucleus so that
there may be some crossing over with
accommodation and miosis
Pupil Testing
Purpose

To examine the afferent and efferent
neurological pathways responsible for
pupillary function
Pupil Testing
Recent onset of the following may be lifeor sight-threatening:


Asymmetry in pupil size
Abnormal response to light or accommodation
Pupil Testing
Procedure consists of four steps




Observation (screen for anisocoria)
Direct and consensual response
Swinging flashlight test
Near reflex test
Pupil Testing
The first three steps should be performed
on every patient
The last step should be done when a
relative afferent pupillary defect (RAPD) is
found in the third step
Observation
In bright and dim illumination
Look for asymmetries in pupil size
Measure pupil size (to the nearest 0.5mm)
Direct Response
In dim illumination
Instruct the patient to look at the distant
target
Shine the light into the patient’s right eye
Observe the size and the speed of the
pupil constriction of the patient’s right eye
This is the direct response or direct light
reflex of the right eye
Consensual Response
In dim illumination
Instruct the patient to look at the distant
target
Shine the light into the patient’s right eye
Observe the size and the speed of the
pupil constriction of the patient’s left eye
This is the consensual response or
consensual light reflex of the left eye
Swinging Flashlight Test
Also known as the Marcus Gunn test
because it is a test for “pupillary escape”
or the Marcus Gunn response
Swinging Flashlight Test
In dim illumination
Move the light between the eyes rapidly,
leaving it on each eye for 3 to 5 seconds
Observe the direction of response
(constriction or dilation) and the size of
each pupil at the moment that the light first
arrives there and during the 3 to 5 second
observation period
Marcus Gunn Response
Also known as a relative afferent pupillary
defect (RAPD)
Marcus Gunn Response
When the afferent pathway (retinal
ganglion cells to optic chiasm) of one eye
is damaged, a light stimulus to the affected
eye will not be able to induce a pupillary
light reflex
As a result, both pupils will be larger when
light is directed into the affected eye
Marcus Gunn Response
When the afferent pathway (retinal
ganglion cells to optic chiasm) of one eye
is damaged, a light stimulus to the normal
eye will still be able to induce a normal
direct and consensual response
As a result, both pupils will be smaller
when light is directed into the non-affected
eye
Marcus Gunn Response
Loss of vision due to corneal, lenticular,
vitreous, refractive, or emotional causes
will not produce the Marcus Gunn
response
Near Reflex Test
Instruct the patient to look at the distant
target
The examiner holds up a target containing
fine detail approximately 25cm from the
patient
Ask the patient to fixate the near target
and look for pupil constriction
Note the speed of the constriction and the
roundness of each pupil
Recording
If all the pupil responses are normal

Record PERRLA, -MG
Pupils Equal Round and Responsive to Light and
Accommodation
Negative Marcus Gunn response
Recording
Describe any pupil abnormalities


Inequality of size (anisocoria)
Direct (D) and consensual (C) responses
based on speed and amount of constriction
on a scale of 0 to 4+
Expected Findings
PERRLA, -RAPD
Direct response is approximately equal to
consensual response
Pupil reaches 90% of maximum size in 5
seconds

Problem with the sympathetic pathway
causes dilation lag so that anisocoria is
greater at 5 seconds than at 12 seconds
Light-Near Dissociation
In normal patients, the amplitude of the
pupil response to light is equal to the
amplitude of the pupil response to near
Light-near dissociation (i.e., near response
is greater than light response) is rare
It may be associated with afferent defects
(blind eye), midbrain defects (Argyll
Robertson pupil), and efferent defects
(third nerve defect)
Argyll Robertson Pupil
Damage to the parasympathetic pathway
Possible causes: neurosyphilis (lesion
around the Edinger-Westphal nucleus),
long-term diabetes, or alcoholism
Presumed neurosyphilis until proven
otherwise
Argyll Robertson Pupil
Both pupils are small and respond poorly
or not at all to light (no direct and
consensual response)
Swift response to near (light-near
dissociation)
Argyll Robertson Pupil
Argyll Robertson Pupil
Adie’s Tonic Pupil
Damage to ciliary ganglion or
postganglionic fibers of the short ciliary
nerve (parasympathetic pathway problem)
Usually unilateral, common in females
The affected eye is dilated and reacts
poorly to light (poor direct and consensual
response)
Adie’s Tonic Pupil
Near reaction is strong, slow, and tonic
When the patient refixates at distance, the
pupil redilates very slowly
Adie’s Tonic Pupil
Adie’s Tonic Pupil
Horner’s Syndrome
Pupillodilator dysfunction
Damage to the sympathetic pathway
Common cause: lung cancer
Signs: ptosis (droopy eyelid), miosis, facial
anhydrosis (sweat gland denervation), iris
heterochromia (congenital Horner’s)
Pupil reacts normally to light and near
Horner’s Syndrome
Horner’s Syndrome
Summary
Anisocoria in light: parasympathetic
problem

Cranial nerve III defect, intracranial pressure,
drug-induced mydriasis, Adie’s pupil, iris
damage, simple anisocoria
Anisocoria in dark: sympathetic problem

Horner’s syndrome, simple anisocoria
References
Neuro-Ophthalmology (Section 5) American Academy of Ophthalmology.
Chapter 4, Pupil.
Primary Care Optometry, pp. 145-147.
The Massachusetts Eye and Ear Infirmary
Illustrated Manual of Ophthalmology, pp.
198-205.