D - Glaucoma Histopath 1 - Week 2 Flashcards
Define ocular perfusion
amount of blood getting to the nerve
Define papilloedema
oedema in the discs of BOTH eyes. (so has to be bilateral. If unilateral oedema, it’s not papilloedema)
How does papilloedema occur?
only occurs from brain/neural causes (e.g. brain tumour)
Does the disc in a patient with only glaucoma (glaucoma optic neuropathy) present with swelling or palor?
NO
What is the major cause of demyelination of nerves in the eye?
Multiple sclerosis
List 6 causes of optic neuropathy that present with swelling/pale/vision afected
Inherited ON
Inflammatory/infectious ON
Demyelinating ON
Toxic ON
Compressive ON
Ischemic ON
Is vision normal in glaucoma optic neuropathy?
yes
Describe how the nerve appearance typically changes as optic neuropathy progresses
Starts with oedema at 1 week. By 2 months, the oedema gets paler, and by 3 months, oedema goes away and is replaced with just palor.
Why can diagnosing optic neuropathy be difficult if a patient has had it for 6 months?
By 6 months, you can’t tell the cause of the disc palor in fundus examination. You would need contact from GP or something from previous appointment to help determine the cause of the pallor
What are the 2 main types of glaucoma? Describe typical IOP levels for each
POAG: may or may not have high IOP
PCAG: always has high IOP (>30mmHg at some stage)
List two mechanisms for angle closure glaucoma. Can they be seen with VH?
- Pupil block/iris impeding angle - can be identified with VH
- Gunk in eye causing TM blockage - need gonio to see this
What is the normal number of RGCs lost per eye per year with normal ageing?
~5000 cells/eye/year (due to apoptosis)
How does GON impact the number of RGCs lost over time?
accelerates loss of neurons by apoptosis.
How does ischemia impact the number of RGCs lost over time? Explain what happens to the RGCs.
Ischemia triggers a sudden/massive loss of RGCs. This results in creating so much gunk etc. that the remaining neurones can no longer survive, causing them to undergo autophagy (a slower loss).
(So a fast big loss, followed by a smaller slower loss)
What aspects of the optic nerve makes it susceptible to neuropathy?
- High mitochondrial density
- Dense capillary plexus in lamina & about the nerve
- Complex pressure gradients on tissues/axons
- Axons, RGC soma & microglia susceptible to increase in IOP
Where is high mitochondrial density found in the optic nerve? Why?
Very dense mitochondria in prelamina region due to the high energy demand of axons going through the lamina to the brain.
What does mitochondrial abnormality promote? (2)
Oxidative damage + inflammation
Energy depletion
Both promote apoptosis
What does “axoplasmic stasis” refer to?
A cease in axonal transport due to energy depletion/mitochondrial abnormality