Optic disk and nerve head Flashcards
how is the optic disk a landmark
-it’s where around 1 million nerve fibres exit the eye
-contains the central retinal artery and vein
what occular diseases are associated with the optic nerve head?
-glaucoma
-papilledema
-papillitis
last two are rare but serious
what is the normal range disk diameter?
1.2-2.27mm
what kind of eyes are optic disks larger or smaller?
-larger in myopic eyes
-smaller in hyoperopic eyes
what is anisometropia?
when there’s a different prescription in each eye usually differing by >1D
what is the optic cup?
the dip when you look at a 2D diagram of the optic nerve head
when looking at the optic disk, when my you become suspicious of glaucoma?
if the CD ratios in each eye differ by >0.2
what supplies optic nerve head circulation?
short posterior arteries
how do nerve fibres at the optic disk look?
they form into around 1000 bundles surrounded by astrocytes
what is the lamina cribrosa?
a cribiform ‘sieve like’ plate made of collagen and elastin that is continuous with the sclera and it’s what nerve fibre bundles at the optic disk pass through
why is the lamina cribrosa significant in glaucoma?
bevause the pressure causes changes to the lamina cribrosa which can cause damage to the nerve fibres that pass through it
how are post-laminar optic nerve fibres different to the ones that go through it? what is it due to?
these ones are myelinated due to oligodendrocytes
what is the dark shadow in the oct of an optic nerve head?
its the central retinal artery’s shadow
what ocular pathologies can an optic disk pit be associated with?
VF (visual field) loss and maculopathy (macular degeneration)
what is disc drusen?
proteinaceous deposits which calcify with time and may cause visual defects
