Week 2.03 OCT Flashcards
What does OCT stand for
Optical coherence tomography
Definition of ocular imaging
- The acquisition, storage, organisation, manipulation, analysis and transmission of images of the human eye by digital systems
Oct has allowed us to
- Better record keeping
- Digital transmission
- Automated analysis of images
- Visualisation of progression – see trends, pictures from last year vs this year
- Improved magnification
- Earlier detection of disease
- Improved diagnostic accuracy
- Accurate and repeatable RNFL measurement
How does OCT work
Shines a laser through the retinal layers
Time domain OCT
- Reflected laser is out of phase
- Known wavelength of laser
- Can tell how deep the penetration is by measuring interference
Laser shone towards eye. Beam splitter in the middle then laser hits retina and reflected back into the receiver
Spectral domain OCT
Can tell how deep the penetration is by analysing the interference patterns obtained
OCT scan
Multiple A scans across a horizontal line
Creates a cross sectional 2D img
Aka B scan
How do we know if optic neuritis or disc drusen
Optic neuritis has an NRR thicker than normal all the way around
Why would we use OCT before and after laser
Pre-operative:
Corneal thickness
Ectasia assessment
Post operative:
Flap assessment
Stromal thickness for secondary treatment
Ongoing ectasia detection
What are the benefits of OCT
Allows visualisation of which retinal layer a lesion is in
Better differential diagnoses
Accurate RNFL assessment
Progression analysis
All other benefits of digital imaging
Limitations of OCT
Affected by anything that blocks the passage of light
- media opacities
- anterior retinal lesions may mask posterior lesions
small field of view
Can’t do peripheral retina
