Anterior Segment Optical Coherence Tomography Flashcards
What was the first cornea image taken with
OCT
OCT principal of operation
Picks up scatter
Why do we use low coherence for OCT
Within a short time/length difference you get strong signal
Why does wavelength matter in OCT
Deeper penetration and better axial resolution
What is the drive for selecting wavelength
Water
What dictates the use of different wavelengths
Water absorption minimization
Penetration length depends on
- source center wavelength
- tissue density
- source power-acquisition rate
- water absorption minimization
What is resolution dependent primarily on in infrared
Source spectral profile
What’s the difference between time domain and Fourier domain
Time domain is much slower
What is the best OCT
Fourier domain
What is the clinical application of being able to use high resolution in OCT
Can see intracrania and intralenticular details
What’s the difference between confocal and OCT
Confocal is way too slow and is primarily used to view cells
How is pachymetry scanned
Take a number of scans really fast. Need to pass through center
-its sequential so you need to do it fast before the eye moves too much
What is the pachymetry map produced by
Interpolation
Why is the OCT map unique
- maps
- and cross sections
Where is the cornea thinnest?
Inferotemporal
When you see a very thin cornea, what should yo expect, especially with it being very thin in the inferior
Keratoconus
LASIK and OCT
Thin, flap=100 microns, need to follow the patient
Pros of OCT
- non contact
- sublayer pach
- 2d data
- easy to acquire data, easy to standardize
- applicable to post op assessment
- measures through opacity
- very high res
- select meridional scans
Cons of OCT
- some developed for retinal imaging and thus require anterior segment adaptor
- limited view
- small penetration depth
- can be slow (time domain)
- software yet to be fully developed
The main advantage of anterior segment OCT in comparison to scheimpflug imaging is
Detailed surface and morphological imaging
What is the only tool we can measure the corneal epithelium with
OCT
Compensatory nature of the epithelium
Not uniform, blanket that covers the stroma. If stroma not uniform, epithelium tries to mask it
Epithelial thickness imaging
Somewhere uniform over the cornea, to approximately 50 microns
What is the most sensitive and telling measurement of corneal health
Corneal epithelium
The epithelial layer in a normal, not pathological Cornea, has a somehow uniform thickness of about 50 microns
True
The epithelial thickness distribution is affected by stromal thickness irregularities
True
The epithelial thickness distribution is affected by corneal pathology
True
