Ocular Lab 8 Questions Flashcards
Difference between ora serrata and peripheral retina
Ora serrata –> end of the retina
Peripheral retina –> outer part of retina that TERMINATES at ora serrata
How wide is the macula
5mm
Where the retina starts to make changes and slope
Fovea
The very center of the fovea
Foveola
What is the cup to disc ratio
Compares the diameter of the cup to diameter of entire disc
-> assess neuroretinal rim thickness over time
How long is the intraocular part of ON
1.5 mm
How long is the intraorbital part of ON
25mm
How long is the intracanalicular part of ON
5 mm
How long is the intracranial part of ON
10mm
How long is the entire ON in length
4-5 cm
Glial plaque (astrocytes) that line the optic cup
Meniscus of Kuhnt
Peripheral continuation of meniscus of Kuhnt that lines surface of neuroretinal rim
Inner limiting membrane of elschnig
Formed by footplates of muller cells, continuous with inner liming membrane of elschnig
Internal limiting membrane of retina
Glial tissue that separates outer retina from bundles of ON fibers
Intermediary tissue of Kuhnt
Collagen separating choroid from bundles of ON fibers
Border tissue of elschnig
Glial tissue situated between border tissue of elschnig and bundles of ON fibers. it merges with intermediary tissue of kuhnt
Border tissue of jacoby
Remnant of meniscus of Kuhnt tissue surround the hyaloid vasculature during development
Bergmeister’s papilla
Size of small discs vertical diameter
<1.5 mm
Size of large discs vertical diameter
> 2.2 mm
Medium sized vertical diameter of optic disc
1.9mm
Where does the ON become myelinated
Just posterior to lamina cribrosa
What is the ON myelinated
For insulation, protection and to speed up travel/transmission to the brain
What is the prelaminar diameter of ON
1.5mm
What is the post laminar diameter of ON
3-4mm
Why is there a difference in diameter between pre/post laminar regions of ON
Because of myelin being laid down behind lamina cribrosa
What are the meningeal layers of the ON continuous with
The meningeal layers of the brain
Bilateral swelling of disc caused by elevated intracranial pressure within the subarachnoid space
Papilledema
Presents with indistinct margins of disc, engorged vessels, small peripapillary hemorrhages and loss of spontaneous venous pulsation
Papilledema
Where does the intracanalicular portion of ON pass through and what travels with it
Lesser wing of sphenoid bone via optic canal with ophthalmic artery
How does the ophthalmic artery sit in relegation to ON when passing through optic canal in lesser wing of sphenoid bone
Inferolateral to the ON
How far from the globe does the CRA pierce the ON
1.25 cm
What is the lamina cribrosa and adjacent pail plexus supplied by
Arterial circle of zinn-haller
What supplies the arterial circle of zinn-haller
Short posterior ciliary arteries
Why does the macula look different from the rest of the retina
- It only has densely packed cones, no rods
- sloped bc of henle fibers
- avascular
- more than one RGCL
- appears more pigmented bc less layers covering the RPE
- high levels of carotenoids
Why does the RNFL run parallel to retina
- axons of gang cells have to run this way to converge into ON
- inline bipolar cells, they do not synapse locally, so their axons are different
Why ON becomes thicker once the NFL passes through the lamina cribrosa
Bc of myelination
3 main causes of papilledema
- inc CSF causing disc to be pushed forward
- veins re engaged bc blood cannot leave eye
- obstruction of axonal flow
Total blood supply to the ON beginning with ICA
ICA –>. Ophthalmic a –> CRA –> capillaries and short posterior a
Where does the CRA branch
In the intraorbital region after the optic canal
Why are diabetics susceptible to ON damage
Bc the capillaries can be easily damaged
Why is the optic disc taller than it is wide
Bc of ISNT rule
- more gang cells coming into top and bottom
Why is the nasal side of ON thicker than temporal region
Temporal only gets in from from macular but nasal gets info form most of peripheral retina
With the isnt rule, what is thickest/thinnest
I - thickest
T - thinnest
