15. OCT for ND Flashcards
What are the orders of the 13 layers of the eye scanned by OCT (inner to outer)?
Internal limiting membrane
Retinal nerve fibre layer
Ganglion cell layer
Inner plexiform layer
Inner nuclear layer
Outer plexiform layer
Outer nuclear layer
External limiting membrane
Photoreceptor layer
Retinal pigment epithelium
Bruch’s membrane
Choriocapillaris
Choroidal stroma
How can we see the 13 layers of the eye via OCT and what differentiates them?
Good, high resolution imaging.
Bright/reflectile or dark/absorption interactions with light differentiate the layers.
What is a TSNIT plot and what does it do?
It is a visual representation of the thickness of the optic nerve head.
Explain this image and the colours.
(pie chart with green, red, and yellow slices)
It’s a sectoral representation of the thickness of the RNFL.
Green means close to age matched norms. Yellow means 95% different from age matched norms. Red means 99% different from age matched norms.
How is OCT useful for the assessment of neurological disorders of vision?
(4 points)
- Assessment of retinal neural layers
- Assessment of retrograde degeneration of the retinal ganglion cell layers
- Macula retinal ganglion cell layers
- Optic nerve RNFL
Stroke/tumour/papilloedema all affect ... and the ... as they’re ....
Stroke/tumour/papilloedema all affect ganglion cells and the retinal nerve fibre layers as they’re directly connected to the cells further upstream.
Papilloedema - ...
Important to differentiate ... from ... as this condition requires .... Many causes of ... can be managed by ....
Papilloedema - elevated disc due to raised intracranial pressure
Important to differentiate true papilloedema from pseudopapilloedema as this condition requires urgent management to identify cause of raised ICP. Many causes of pseudopapilloedma can be managed by routine review.
Some causes of psuedopapilloedema
(3 points)
- optic nerve head drusen - results in undulated shadow going over drusen
- obliquely inserted optic discs
- crowded optic disc - absence of cuppin
What is wrong with white on the sectoral RNFL map compared to red?
Both are bad, red is too thin but white is too thick.
Retrograde damage to ganglion cells with brain lesions
More than ...% of RGC are located in ... and high resolution OCT can identify ... of this area. Any ... can be indicative of retrograde transynaptic degeneration.
Retrograde damage to ganglion cells with brain lesions
More than 50% of RGC are located in macular region and high resolution OCT can identify subtle thinning of this area. Any thinning can be indicative of retrograde transynaptic degeneration.
Multiple sclerosis
... and ... can lead to subtle ... of the ....
Multiple sclerosis
Swelling and inflammation can lead to subtle bulging of the ONH.
How would you label defects of the macular region (thinning of the macula is reflected in VFTs)?
Same way as a VFT, just flip everything.
