1. Eye movements, reflexes and control
01/20/2015
Virginia Lam
Daniella Marks

2. Component of pupillary reflex pathway
Afferent pathway:
Optic disc, optic nerve (CNII), optic chiasm optic tract and pretectal nucleus (dorsal midbrain)
Efferent pathway
Oculomotor nerve Edinger westphal nucleus, ciliary ganglion

3. Assessing pupillary reflexes
For integrity of pupillary light reflex pathway through pupil size and reaction
Light reflex test
Swinging flashlight test
Accommodation
Near reflex test

4. Light reflex pathway

5. Light reflex test Assess: How: Result:
CN II, III, optic tract, Pretectal nucleus, Edinger nucleus and ciliary ganglion
How:
Dim environment
Ask patient to fixate a distant target
Illuminate the right eye from right side, and left from left side
Don’t stand in front of patient to avoid accommodation
Result:
Brisk simultaneous equal response on the pupil you shine light on (direct response) and contralateral pupil (consensual response)
Good reference link:

6. Swinging flashlight test
Assess:
Compare the direct and consensual response of both eyes
How:
Same condition as light reflex test and check reflex first
Then swing the light source rhythmically and swiftly from one eye to the other
Observe what happen to the pupil of the eye you are shining light on, and its contralateral eye
Result:
Pupil should constrict or stay the same size
If it dilates when light is shone on, it means the light reflex is seaker than consensual reflex, suggesting optic nerve pathology
Abnormal response is known as relative affective pupillary defect (RAPD) or Marcus Gunn pupil
NB: it is a comparative test, so no bilateral RAPD!

7. Near reflex test Assess: How: Result: The ability to accommodate
Ask patient to focus on a distant target, and then a near point (about an arm length away)
Observe the pupillary reflex and eye movement
Result:
Eye position: vergence
Brisk pupillary constriction

8. Pupil reflex Test: Shine light on right eye
CN II Lesion (complete): no direct and consensual
CN III lesion (blue arrow):
No direct but with consensual

9. Argyll Robertson Pupil
Seen in tertiary neuro syphillis, but can also found in diabetic neuropathy
Pupils can accommodate but do not react
Affect Edinger Westphal nucleus

10. Extrinsic Eye Muscle Function
(Up and In)
(Down and In)
Imagine each muscle as if it were acting alone.

11. Testing the Muscles Step 1: put the muscle in relative isolation
Select new starting position (different from it’s neutral position
Step 2: ask the patient to make a specific eye movement
Step 3: observe whether patient is capable of moving eye

12. Medial and Lateral Rectus
In this case, the actual movement and testing position are the same
Medial rectus
Actual movement: move pupil medially
Test: ask patient to look toward their nose
Lateral rectus
Actual movement: move pupil laterally
Test: ask patient to look toward their ears
Nose
MR = Adducts
Nose
LR = Abducts

13. Inferior and Superior Rectus
Put the eye in a position where no other muscles are capable of moving eye
Abducting the eye accomplishes this
Now only looks at elevation/depression
Inferior rectus
Actual movement: downwards and inwards
Test: ask the patient to look out and down
Superior rectus
Actual movement: upwards and outwards
Test: ask the patient to look out and up
Nose
Nose

14. Inferior and superior oblique
Put the eye in a position where no other muscles are capable of moving eye
Adducting the eye accomplishes this
Now only looks at elevation/depression
Inferior oblique
Actual movement: upwards and outwards
Test: ask the patient to look in and up
Superior oblique
Actual movement: downwards and outwards
Test: ask the patient to look in and down
Nose
Nose

15. Eye Movements and Cranial Nerves
LR6 SO4 AO3
Lateral rectus – VI
Superior oblique – IV
All others - III

16. Cranial Nerve Palsies CN Normal function Palsy CN III Motor supply to:
Levator palpebrae superioris
MR, IR, SR, IO
Autonomic motor supply to:
Sphincter pupillae
Ciliary body
Motor function of affected eye:
Ptosis
Divergent squint – horizontal+vertical diplopia
Autonomic function of affected eye:
Dilated pupil
Unreactive to direct/consensual light reflex
CN IV SO
Upward and extorsion deviation
Torsional diplopia – patient will tilt head away from side of lesion (neck pain!)
Vertical diplopia
CN VI LR
No lateral movement
Convergent squint – horizontal diplopia

17. Cranial Nerve Palsies Diplopia worsens when:
Unaffected eye looks away from lesion side
Looking down (affected eye stuck in up+out position)
Unaffected eye looks towards lesion side

18. What are 3 types of eye movement control?
Track a target
Stabilize a target
Scan between targets

19. What are 5 ways to control eye movements?
Medial longitudinal fasciculus (MLF)
Lateral conjugate (together) gaze
Voluntary saccades
Quick flickers in response to stimuli
Vestibulo-ocular reflex
Stabilize the eyes to compensate for head movement
Frontal eye field
Visual attention and conjugate gaze
Visual association areas
Process information

20. Internuclear Opthalmoplegia
E.g. Lesion in right MFL
Patient looks right
Right eye abducts (R CN VI), left eye adducts (L CN III)
Patient looks left
Right eye remains centered (R CN III), left eye abducts (L CN VI)
Patient able to converge and accommodate eyes
Horizontal diplopia worse when looking left
Compensation: head slightly rotated to the left
In damaged MLF:
Side of MLF pathway damage results in ipsilateral damage in adduction
Nuclei are intact – can still accommodate
Note: this is the patient’s perspective.

21. Vestibulo-ocular reflex
As the head is rotating axially in a given direction, the lateral semicircular canal makes both eyes look to opposite side
Clinical relevance:
Brain stem function testing
Doll’s eye sign

22. Vestibulo-Ocular Reflex
E.g. Head moves right
Right SCC activated
Stimulates right CN VIII
Activates contralateral CN VI nucleus
MLF activated
Left CN VI activated (left lateral rectus)
Right CN III activated (right medial rectus)
Look left
Damage:
Eyes drift to side of lesion due to unopposed vestibular nuclear system on opposite side
Damage: Eyes drift to side of lesion

23. Nystagmus Fast and slow phase
Named according to the fast “flicker”
Fast movement to the right, right nystagmus
Consequence of damage to vestibulo-ocular system
Remember: left VOR makes you look right
Damage to left VOR: eyes drift to left (slow phase)
Right nystagmus (fast phase to the right)

24. Clinical Relevance of VOR and Nystagmus
Cold caloric test
Imperative for assessing brain function
Procedure
Cold water is injected into the ear – affects SCC
Eyes slowly drift to side of water (analogous to lesion)
Fast correction to midline
E.g. Water injected into left ear
Left SCC affected
Eyes drift to the left, right nystagmus to correct it
Damage
CNS depression: fast phase is not so fast…
Coma/brain stem death: no reaction at all

25. Question:
Mr Smith visits your GP surgery, presenting with the following:
What do you want to know in terms of
Eye lid movement?
Resting eye position?
Vision?

26. How is it different from Horner’s Syndrome?
Eye lid movement
Can he open his eye?
Eye position?
What is his resting eye position
How can it move
Vision
Any double vision
When it is worse
How is it different from Horner’s Syndrome?