OCT Flashcards
Optic Disc Morphology is analyzed at how many points on the ONH circumference
255 points
A smaller disc is more likely to produce false ___ on OCT
Positives
A larger disc is more likely to produce false ___ on OCT
Negatives
On OCT, what RNFL thickness readings are most often affected in early GLC?
Avg and Inferior
Avg RNFL thickness between fellow eyes should be within how many microns?
10 microns
RNFL thickness graph:
White indicates…
THICKEST 5%
RNFL thickness graph:
Green indicates…
90% of NORMALS
RNFL thickness graph:
Yellow indicates…
THINNEST 5%
RNFL thickness graph:
Red indicates…
THINNEST 1%
RNFL thickness graph:
Gray indicates…
Disc area did not match normative data or no normative comparison available
T/F: if a patient’s RNFL thickness falls within the ‘white’ they do not have GLC
FALSE; can start with really thick RNFL
What is considered and ‘abnormal’ RNFL thickness?
Overall avg below 5% (red or yellow)
Any quadrants below 5% (red or yellow)
Any clock hour below 1% (red)
Where is the best place to look for GLC/dips on the TSNIT curve?
Between Temp & Sup and between Inf & Temp
Large discs have ___ (higher/lower) sensitivity fir early GLC detection, resulting in more false ___
Lower; negatives
ERM may ___-estimate RNFL and mac thickness
OVER
CAT may ___-estimate RNFL thickness
UNDER
What is the relationship between axial length and RNFL?
The longer the eye, the thinner the RNFL
**for every 1mm inc in axial length, RNFL thickness decreases by 2.2µm
Longer axial length is associated with risk of OCT false ___
POSITIVES
(Thinness is caused by longer axial length, not by GLC)
T/F: it is not possible to to increase RNFL thickness over time
TRUE!
If thickness appears to increase, it is not a reliable scan!
Vignette artifact is usually due to
A really really small nerve
How can you tell if the OCT is decentered to the macula (instead of the ON)?
Lack of BV in RNFL deviation map
Shifted nerve bundles can cause false ___
Positives
