Anterior Segment Optical Coherence Tomography

Question 1

What was the first cornea image taken with

Answer 1

OCT

Question 2

OCT principal of operation

Answer 2

Picks up scatter

Question 3

Why do we use low coherence for OCT

Answer 3

Within a short time/length difference you get strong signal

Question 4

Why does wavelength matter in OCT

Answer 4

Deeper penetration and better axial resolution

Question 5

What is the drive for selecting wavelength

Answer 5

Water

Question 6

What dictates the use of different wavelengths

Answer 6

Water absorption minimization

Question 7

Penetration length depends on

Answer 7

• source center wavelength
• tissue density
• source power-acquisition rate
• water absorption minimization

Question 8

What is resolution dependent primarily on in infrared

Answer 8

Source spectral profile

Question 9

What’s the difference between time domain and Fourier domain

Answer 9

Time domain is much slower

Question 10

What is the best OCT

Answer 10

Fourier domain

Question 11

What is the clinical application of being able to use high resolution in OCT

Answer 11

Can see intracrania and intralenticular details

Question 12

What’s the difference between confocal and OCT

Answer 12

Confocal is way too slow and is primarily used to view cells

Question 13

How is pachymetry scanned

Answer 13

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

Question 14

What is the pachymetry map produced by

Answer 14

Interpolation

Question 15

Why is the OCT map unique

Answer 15

• maps

- and cross sections

Question 16

Where is the cornea thinnest?

Answer 16

Inferotemporal

Question 17

When you see a very thin cornea, what should yo expect, especially with it being very thin in the inferior

Answer 17

Keratoconus

Question 18

LASIK and OCT

Answer 18

Thin, flap=100 microns, need to follow the patient

Question 19

Pros of OCT

Answer 19

• 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

Question 20

Cons of OCT

Answer 20

• 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

Question 21

The main advantage of anterior segment OCT in comparison to scheimpflug imaging is

Answer 21

Detailed surface and morphological imaging

Question 22

What is the only tool we can measure the corneal epithelium with

Answer 22

OCT

Question 23

Compensatory nature of the epithelium

Answer 23

Not uniform, blanket that covers the stroma. If stroma not uniform, epithelium tries to mask it

Question 24

Epithelial thickness imaging

Answer 24

Somewhere uniform over the cornea, to approximately 50 microns

Question 25

What is the most sensitive and telling measurement of corneal health

Answer 25

Corneal epithelium

Question 26

The epithelial layer in a normal, not pathological Cornea, has a somehow uniform thickness of about 50 microns

Answer 26

True

Question 27

The epithelial thickness distribution is affected by stromal thickness irregularities

Answer 27

True

Question 28

The epithelial thickness distribution is affected by corneal pathology

Answer 28

True