Pupillary Abnormalities

Question 1

What is pupillary reflex?

Answer 1

Shining light in one eye causes constriction of pupils in both eyes. Constriction of pupil in the eye where light in shone is called direct light reflex and constriction of pupil in the fellow eye is called consensual light reflex.

Question 2

Pupillary reflex pathway

Answer 2

Afferent pathway
- Light enters pupil and stimulates retina
- Retinal ganglion cells transmit light signal to optic nerve
- Afferent fibres travel along optic nerve from retina to pretectal nucleus in mid brain at the level of superior colliculus
- At the optic chiasm, fibres from nasal retina decussate to optic tract on opposite side and terminate in contralateral pretectal nucleus
- Fibres from the temporal retina remain uncrossed and terminate in ipsilateral pretectal nucleus
- Fibres from optic tracts project and synapse in pretectal nuclei in dorsal midbrain in collicular region
- Each pretectal nucleus is connected with Edinger Westphal nuclei of both sides via internuncial fibres (consensual response)

Efferent pathway
- Edinger-Westphal nucleus projects pre-ganglionic parasympathetic fibres which travel along the oculomotor nerve (CN III) to form the efferent pathway
- Pre-ganglionic fibres travel along the CNIII (inferior division, nerve to inferior oblique) and synapse on post ganglionic parasympathetic vibes in ciliary ganglion
- Post-ganglionic fibres travel via short ciliary nerves to supply the pupillary sphincter causing constriction of pupil and ciliary muscles for accommodation

Question 3

What is consensual pupillary light reflex?

Answer 3

Light information given to 1 eye is transmitted equally to both pupils because:
1. Hemidecussation of nasal fibres at optic chiasm
2. Light information received from each pretectal nuclei given to both Edinger-Westphal nuclei

Question 4

What is pupillary near reflex?

Answer 4

• Pupils constrict (miosis) to a near target
• Near triad
  1. Convergence (in-turning of both eyes)
  2. Accommodation (contraction of ciliary muscles)
  3. Miosis

Question 5

Causes of light near dissociation

Answer 5

1. Adie’s/tonic pupil
2. Argyll Robertson pupils
3. Parinaud syndrome

Question 6

What is Adie’s pupil?

Answer 6

• Lesion is at the ciliary ganglion/ short posterior ciliary nerves
• Anisocoria worse in light
• LARGE pupil unreactive to light, reactive when looking at near object
• Unable to constrict much/sluggish during direct pupillary reflex test
• Absent deep tendon reflex (Adie’s syndrome)
• Constricts with 0.1% pilocarpine
• Vermiform (worm-like) movements of the iris

Question 7

Light near dissociation: afferent or efferent problem?

Answer 7

Efferent problem

Question 8

What is Argyll Robertson’s pupils?

Answer 8

• Syphilis selectively affects the midbrain (dorsal)
• Uveitis due to syphilis –> Sticky iris (Iritis) –> Small and irregular pupil
• Anisocoria worse in light
• Pupil unreactive to light, reactive when looking at near object
• Unable to constrict much/sluggish during direct pupillary reflex test

Question 9

What is parinaud syndrome?

Answer 9

• Lesion in dorsum midbrain where the vertical gaze centre is at, patient will have vertical gaze palsy
• Accommodation pathway is ventral midbrain whereas pupillary light reflex pathway is dorsal midbrain. Hence, only pupillary light reflex is affected
• Anisocoria worse in light
• LARGE pupil unreactive to light, reactive when looking at near object
• Unable to constrict much/sluggish during direct pupillary reflex test

Question 10

Lesions in parinaud syndrome can be caused by

Answer 10

Hydrocephalus
Pinealoma
Tumour
AV malformation
Stroke
Multiple sclerosis
Wernicke’s

Question 11

Clinical features of parinaud syndrome

Answer 11

• Supranuclear gaze palsy (Up gaze affected)
• Lid retraction
• Convergence-retraction nystagmus (Use optokinetic drum: Patient’s eye will pursuit downwards but saccade upwards = Convergence retraction)
• Large pupil
• Light near dissociation
• Convergence spasm (When patient look up, the eyes converges)
• Nystagmus

Question 12

RAPD: afferent or efferent problem?

Answer 12

Afferent problem
- optic nerve problem

Question 13

What are the 2 broad causes of RAPD?

Answer 13

1. Optic neuropathy
2. Severe macular dysfunction

Question 14

Causes of optic neuropathy

Answer 14

1. Glaucoma (Most common)
2. Ischemic Neuropathy (DM/ AION/ NAION)
3. Demyelinating
4. Compressive (Tumor - Sphenoid wing/ pituitary/ optic nerve glioma/ meningioma/ thyroid related orbitopathy - large muscle belly/ ICA aneurysm)
   - Lesion at optic tract can lead to differential dilation also
   - Retinoblastoma

Question 15

How does light near dissociation occur?

Answer 15

Accommodation and pupillary light reflex are separate pathways
Accommodation pathway is ventral midbrain whereas pupillary light reflex pathway is dorsal midbrain

Question 16

Causes of severe macular dysfunction

Answer 16

1. Ischemic CRVO
2. CRAO
3. Macular retinal detachment

Question 17

Anisocoria worse in the light means

Answer 17

• Abnormality in the iris sphincter
• Inability to constrict in pathological eye
• Dilated pathological pupil
• LARGE pupil unreactive to light, reactive when looking at near object
• Parasympathetic problem
• Unable to constrict much/sluggish during direct pupillary reflex test

Question 18

Causes of anisocoria worse in light

Answer 18

• Adie’s pupil (constricts with 0.1% pilocarpine)
• Argyll Robertson’s pupil
• Parinaud pupil
• Surgical 3rd nerve palsy (constricts with 1% pilocarpine)
• Pharmacological (no constriction with 1% pilocarpine)
• Trauma/ Mechanical - Rupture of pupillary sphincter

Question 19

Anisocoria worse in dark means

Answer 19

• Abnormality in the iris dilator
• Inability to dilate in pathological eye
• Constricted pathological pupil
• SMALL pupil unreactive to light, reactive when looking at near object
• Sympathetic problem
• Unable to constrict much/sluggish during direct pupillary reflex test

Question 20

Causes of anisocoria worse in the dark

Answer 20

Horner’s syndrome
Physiological anisocoria
Sympathetic hypersensitivity

Question 21

Symptoms of Horner’s syndrome

Answer 21

Horner’s Syndrome is characterized by
- ipsilateral miosis (constricted pupil) + anisocoria worse in the dark
- partial ptosis
- anhidrosis (in pre-ganglionic cases)

Other symptoms
- Relative enophthalmos
- Heterochromia iridis (seen in congenital cases because the sympathetic innervation is believed to be important for the normal colour development of the iris)

Question 22

Causes of Horner’s syndrome

Answer 22

1. First order neuron
   - Lesion of hypothalamus, brainstem and spinal cord
   - Brainstem stroke: Lateral Medullary Syndrome (LMS)**
   - Demyelination: MS
2. Second order neuron (pre-ganglionic) - c8-t1
   - Lesions of neck and high thorax
   - Lung apex –> Pancoast tumor**
   - Mediastinum –> Tumour
   - Neck –> Lymphadenectomy, thyroid malignancies
3. Third order neuron (post-ganglionic) - Superior cervical ganglion
   - Lesions follow the course of ICA
   - Internal carotid dissection**
   - Cavernous sinus tumour

Question 23

What clinical feature differentiates the level of lesion in Horner’s syndrome?

Answer 23

1st order neuron: Ipsilateral anhidrosis of arm and face
2nd order neuron: Ipsilateral anhidrosis of face only
3rd order neuron: NIL anhidrosis

Question 24

Investigations for Horner’s syndrome

Answer 24

Step 1: Confirm Horner’s - cocaine test or apraclonidine test*
- Cocaine test: If the affected eye does NOT dilate → means that there is a horner’s syndrome (clinically significant > 1mm)
- Apraclonidine eye drops reverses anisocoria worse in dark and reverses ptosis

Step 2: Localising lesion
- Hydroxyamphetamine test, phenylephrine test
- Differentiate third from first/second order neuron
- If the pupil dilates, the lesion is preganglionic; if not, it is postganglionic.
- MRI brain, CT neck, angiogram to check for other causes of horner’s

Question 25

Physiological anisocoria

Answer 25

Commonest Pupillary function is normal Degree of anisocoria remains the same in the light and dark Not more than 1mm

Question 26

Normal VF extends

Answer 26

superiorly 50 degrees nasally 60 degrees inferiorly 70 degrees temporally 90 degrees