Vision (optic nerve etc)

Question 1

Describe the function of the optic nerve and it’s course

Answer 1

The optic nerve. Is a paired nerve that transmits visual information from the retina to the brain.

It goes from the Optic disc via the optic canal.
It runs posteromedially to the optic chiasma where Partial decussation occurs of fibers from temporal visual fields of both eyes.

Then
optic tract
to
lateral geniculate nucleus where most of it’s axons terminate

Here information is relayed to the visual cortex in the occipital lobe of the brain.., other axons terminate in the pretectal nuclei for reflexive eye movements. and the others terminate superior colliculus. (sleep wake cycle)

Question 2

Describe the effects of bilateral hemianopia

Answer 2

Bilateral hemianopsia is where vision is lost in the lateral fields of both eyes and only half is seen.

Information from the temporal visual fields fall on the medial retina.

Question 3

What can cause BH?

Answer 3

Damage to the optic nerve in the optic chiasm.

Pituitary tumors that compress/damage the nerve

When pressure is on the nerve visual impulse is affected and there is an inability to view temporal or peripheral vision.

Pituitary is adjacent – adenomas and craniophyaryngomas. Meningomas. Vascular origin could be aneurysm of the anterior communicating artery.

Question 4

Describe the optic disc.

Answer 4

Point of exit for ganglion cell axons leaving the eye. Point where retinal ganglion cells come together
Beginning of the optic nerve.

point for major blood vessels to supply the retina.no rods or cones overlying therefore corresponds to a small blind spot in each eye.