Ocular: Optic Nerve By OCT Flashcards
Optic nerve C/D ratio rarely differs between the two eyes by more than _______
0.1
If there is a > 0.1 difference between the C/D ratio between the eyes, is this significant?
Yes, risk factor for Glaucoma
Central depression representing absence of axons
Optic cup
Lamina cribrosa pores often visible, especially in large cups are known as __________
Lamina dots
Neuroretinal rim contains _________ and ________
RGC axons and glial cells
Having a large optic disc, means you will often have a ________ optic cup
Large
Does having a large optic disc mean you will have more ganglion axons?
No, ganglion axons do not differ based on disc size
RNFL thickness __________ with age w/ loss of _________
Decreases
Ganglion cells
Mean RNFL thickness in patients 5-15 years of age
107.6 +/- 1.2 um
Mean RNFL thickness in patients 20-78 years of age
97.2 +/- 9.7 um
Caucasian patients generally have the ________ Disc Area
Smallest
Patients of African descent have the _________ Disc Area
Largest
When magnification is accounted for: Hyperopic eyes above +4D have ________ discs
Smaller
When magnification is accounted for: myopic eyes with more than -8D have _________ discs
Larger
What is considered a large Disc Area size?
Over 2.1 mm^2
What is considered a small Disc Area size?
Under 1.5 mm^2
Magnification correction factor for 90D lens
1.3x
Magnification correction factor for 78D lens
1.1x
What is considered a small disc vertical diameter?
< 1.5 mm
What is considered an average disc vertical diameter?
1.5-2.0 mm
What is considered a large disc vertical diameter?
> 2.0 mm
Vertical disc diameter is ________ than horizontal diameter
Greater
Zeiss Cirrus OCT: utilizes consecutive radial _________ measurements along the nerve
BMO-HRW
BMO
Bruch’s membrane opening
BMO is an anatomic boundary of the _____________
Neuro-retinal rim tissue
BMO-HRW is the distance between _________ and _________ along the plane of the BMO
BMO and ILM
What is BMO-MRW?
- neuro-retinal rim thickness as the minimum distance between the BMO and ILM
MRW
Minimum rim width
The Heidelberg Spectralis OCT uses what BMO measurement?
BMO-MRW
What measurement is made perpendicular to the ILM and therefore is perpendicular to the axis of neural tissue as ILM and NFL are parallel?
BMO-MRW
What measurement does not take into account nerve fiber trajectory into the disc?
BMO-HRW
What measurement is made based off of the clinically visible disc margin?
DM-HRW
Macular axons travel towards the nerve as a __________ bundle
Papillomacular bundle
RGC axons from the nasal half of the retina travel where?
Directly towards the nerve
RGC axons from areas of retina temporal to the fovea travel in what way? What are these bundles of axons called?
Arc around the fovea to the nerve
Called arcuate bundles
RNFL thickness can be plotted horizontally as __________ or __________
TSNIT or NSTIN
Is TSNIT or NSTIN becoming increasingly more common?
NSTIN due to temporal RNFL being in the middle of
In the RNFL thickness plot, what are the 2 main bundle peaks known as the double hump on a healthy RNFL horizontal plot?
Supero-temporal
Infero-temporal
Normal order of descending thickness of RNFL
ISNT
Retinal vessels develop along peak _________ densities
Ganglion cell
What is a good filter to use to visualize the RNFL?
Red-free filter
Peak RNFL bundles in high myopia are _________ and shifted ___________
Straightened and shifted temporally
In instruments that do not correct for patients refractive error, how are RNFL bundles shifted in high myopia? This non-correction can lead to a so called ‘disease’ known as __________
Shifted temporally
Red disease
What are the two secondary RNFL bundle peaks? And what do they correlate with?
Supero-nasal
Infero-nasal
Correlate with nasal retinal vessels emerging from disc
RNFL is thinnest at the disc where?
Temporally
RNFL is overall thinnest in what region? And why?
In the fovea where there are no RGC axons
Disc-Fovea angle range is from ________ and __________
-20º and +9º
Disc-Fovea angle is about _______ degrees on average
-6
Do disc-fovea angles vary between the eyes of a patient?
Yes, they can
Abnormal disc-fovea angles that are not compensated for by OCT can lead to false positives for __________
RNFL thinning
With Excyclotorsion, how are the RNFL bundles shifted? And why?
Shifted temporally due to the very negative disc-fovea angle
A very positive disc-fovea angle will shift _______ peak RNFL bundle in which way? (Relative to database)
Very positive disc-fovea angle will shift inferior peak RNFL bundle temporally
A large portion of ganglion cells are concentrated where?
In the macula
Why do we measure ganglion cells thickness?, why is it important?
RGC dendrites die FIRST, then cell bodies, then axons
Can detect damage sooner when looking at ganglion cells thickness
Topcon’s Maestro (SD-OCT) measures 2 different ganglion cell layer thicknesses: what are they?
GCL +
GCL ++
GCL+ is measurement of what thickness?
Ganglion cell and inner plexiform layer thickness
GCL ++ is measurement of what thickness?
Ganglion cell, inner plexiform and retinal nerve fiber layer thickness
Topcon’s Triton SS-OCT
Retina thickness measurement is between what boundaries?
The ILM-OS/RPE boundaries
Topcon’s Triton SS-OCT
RNFL thickness measurement is between what boundaries?
The ILM-RNFL/GCL boundaries
Topcon’s Triton SS-OCT
GCL+ thickness measurement is between what boundaries?
The RNFL/GCL-IPL/INL boundaries
Topcon’s Triton SS-OCT
GCL++ thickness measurement is between what boundaries?
The ILM-IPL/INL boundaries
Temporal raphe divides the temporal RNFL into _________ and _________
Superior and inferior halves
Why is glaucomatous damage often asymmetric across the horizontal midline? And what is this sign called?
Due to the superior and inferior segregation of nerve fibers into the disc.
Temporal Raphe sign. Helps differentiate glaucoma vs. non-glaucoma issues
