OCT Document

Question 1

OCT stands for

Answer 1

Optical Coherence Tomography

Question 2

OCT does what

Answer 2

Provides cross section and tomographic images in biological tissues.

Easy, non invasive option.

Not affected by axial length, refractive error and some cataracts

Question 3

Why can’t you use OCT for everything?

Answer 3

Light is easily scattered, absorbed by biologic tissues.
Penetrates only 2mm
Can only image optically accessible tissues like the eye

Question 4

Resolution of ultrasound and OCT

Answer 4

Ultrasound is 100

OCT is 5

Question 5

OCT low coherent interferometry

Answer 5

Compares 1 optical beam with another

Question 6

How does OCT work

Answer 6

Splits light into two beams using a mirror.

One is transmitted into patients eye, reflects off structures and back to the mirror.

Other is reflected. Combines with beam from pt eye.

Combined beam goes into photodetector and time delay is measured.

Question 7

OCT signal depends on what

Answer 7

Amount of light absorbed, transmitted or reflected.
Transparent structures are cool or black
Dense structures are hot or white

Question 8

Normal retinal imaging 
RNFL
Plexiform 
Nuclear 
PR 
RPE/Bruchs/Chorio

Answer 8

RNFL is bright with red backscatter. 
Plexiform has intermediate reflectivity 
Nuclear has minimal reflectivity 
Photoreceptors are dark. Least reflective. 
RPE/bruchs/chorio: Highly reflective.

Question 9

What causes increased reflectivity

Answer 9

Infiltrates, scar, exudate, hemes
Exudate- reflective and shadow
Hemes- Reflective and scatter and shadow

Question 10

What causes decreased reflectivity

Answer 10

Edema, hypo pigmented RPE
Serous fluid has few cells and no scatter
Blood has many cells and more scatter

Question 11

OCT cirrus captures dense cube of scan in how many seconds

Answer 11

2.4