Eye Neuroanatomy

Question 1

Describe the pathways for the pupillary light reflex and consensual light reflex.

Answer 1

Question 2

If a patient comes in with no pupillary light reflex, where could the lesions be?

Answer 2

1. Optic Nerve
2. Retina
3. Pretectal Nucleus
4. Edinger-wesphal Nucleus

Question 3

If a patient comes in with no contralateral light reflex, where could the lesions be?

Answer 3

1. Edinger-Westphal Nucleus
2. Ciliary Ganglion

Question 4

Describe the visual pathway. How does signals move for the pupillary light reflex?

Answer 4

Light –> Retina –> Optic Nerve –> Optic Chiasm –> Optic Tract –> Lateral Geniculate Nucleus (thalamus) –> optic radiation –> primary visual cortex

Optic Tract gives off collaterals to the midbrain (pretectal nucleus)

Question 5

The optic radiation is made of upper fibres and lower fibres (meyer;s loop). What do each part control?

Think of what would happen if each had lesions.

Answer 5

Upper Fibres: carry fibres representing inferior visual field
Lower Fibres (Meyer’s Loop): carry fibres representing superior visual field

Question 6

The primary visual cortex is technically made up of two regions. What are these two regions?

Answer 6

1. Primary Visual Cortex (VC1)
2. Visual Association Area (for interpreting what is seen) (VC2)

Question 7

From the primary visual cortex, there are two pathways that the fibres project to for interpretation. What are these two pathways and what are their functions?

Answer 7

1. Ventral Visual Pathway: Underside of Temporal Lobe; Form & Colour
2. Dorsal Visual Pathway: Posterior Parietal Lobe; Motion & Spatial Rs

Question 8

Abducens Nerve (CN6)
- Course
- Innervation
- Function
- Lesion if affected

Answer 8

• pons (pontomedullary junction) –> via posterior cranial fossa, enters middle cranial fossa via cavernous sinus –> superior orbital fissure
• lateral rectus (LR6)
• adducted at rest, cannot abduct when looking

Question 9

Trochlear Nerve (CN4)
- Course
- Innervation
- Function
- Lesion if affected

Answer 9

• midbrain (level of inferior colliculus) –> cavernous sinus –> superior orbital fissure
• Superior Oblique
• Downward movement and outward movement
• involved eye elevated on forward gaze

Question 10

Oculomotor Nerve (CN3)
- Course
- Innervation
- Function
- Lesion if affected

Answer 10

• midbrain (level of inferior colliculus) –> cavernous sinus –> superior orbital fissure
• All extraocular muscles except SO4 and LR6