Optic Nerve Flashcards
The axons leave the eyeball through the?
Lamina crirosa sclerae
How does the optic nerve differe from all the other nerves?
It is not a peripheral nerve but rather a central nervous system tract and it has no ability to regenerate if it is damaged
What makes up the retrobulbar part of the optic nerve?
- The intra-orbital
- Intracanalicular
- Intra-cranial
What is theocular part made of?
The optic disk
What makes the retro-bulbar relatively resistant to ocular occlusion?
There is a complex anastomosis of various branches of the internal carotid artery
Why is the optic disk prone to vascular occlusion?
Because it has short posterior ciliary branches of the internal cariotid artery
What are the symptoms of optic nerve disease?
- Loss of vision
- Retrobulbar pain occurs only in optic neuritis
What are the signs of optic nerve damage?
- Decreased VA
- Decreased VF
- Pupil:sluggish reaction to light
- Disc appearance may appear swollen because of raised intracranial pressure
- or pale due to optic atrophy
What are the 4 characteristics of the optic disc that we must always assess on opthalmoscopy?
- The margin/contour and whether it is well defined
- The colour which is usually pink
- The cup or C/D ratio
- The blood vessels or venous pulsation to ensure that there is not cental retinal venous occlusion
What does this image depict?
Name 7 characteristics that is the classical appearance of optic swelling?
- Disc hyperaemia and dilated capillaries on the disc
- The disc margin/contour is indistinct
- Disc and retinal venous congestion
- Loss of retinal venous pulsation
- Cotton wool spots on and around the disc
- Hard exudates around the disc
- Nerve fibre layer haemorrhages on and around the disc
What are the two exceptions to the classical appearance
- Anterior IschaemicOptic Neuropathy
- Central Retinal Venous Occlusion
What are transient obscurations of vision?
Multiple episodes of blurred vision each which last for only a few seconds
Is optic disc swelling unilateral or bilateral?
It is usually bilateral and symmetrical
What is the Foster-Kennedy syndrome?
A condition causing unilateral optic disk swelling in raised intracranial pressure
What happens when there is a intracranial tumour?
There is atrophy on the intracranial part of the intra-cranial nerve and this means that the contralateral optic disc gets swollen because the affected side has lost its nerve fibres
Define optic neuritis
Optic neiritis is inflammation of the optic nerve
What is papillitis?
Inflammation of the optic disc
What is retrobulbar neuritis?
Inflammation of the retrobulbar part of the optic nerve
What are the causes of optic neuritis?
- multiple sclerosis in adults
- Bacterial-TB and Syphillis
- Viral- mumps, measles, chicken pox and these usually affect children
- Systemic inflammations- sarcoidosi
What are the clinical symptoms of optic neuritis?
Unilateral loss of vision-which is usually dramatic and maximal within a few days of onset
Vision usually improves 2- 3 weeks later and the rate and degree of visual recovery is variable
Retrobulbar pain is only in retrobulbar neuritis
What are 4 signs of optic neuritis on ophthalmoscopy?
- Decreased VA
- VF defect: central scotoma
- Pupil is sluggish to light
- On ophthalmoscopy- There is papillitis(optic disc swelling)
What is Anterior Ischaemic Optic Neuropathy?
Partial or complete infarction of the optic disc due to posterior ciliary arterial occlusion
What are the causes of anterior ischaemic optic disc neuropathy?
arteriosclerosis and giant cell arteritis
