Topography (Walker - Test 3)

Question 1

Why is corneal topography important?

Answer 1

Allows us to describe and understand what retinal image we are getting. Gives us numbers, elevation, to a more precise number, and assess ocular/corneal shape. **Keratoconus is most common irregular cornea you will see

Question 2

Classic reasons to use a corneal topographer?

Answer 2

Dz evaluation and monitoring: curvature changes, edema & CL eval: irregular corneas and ortho-k monitoring

Question 3

Advanced reasons to use a corneal topographer?

Answer 3

Tear film eval, eval of candidacy of refractive surgery, and custom CL fitting (empirical GP lens design)

Question 4

Tomography vs Topography?

Answer 4

Tomography is both surfaces and topography is anterior surface. Tomography: allows a 3-D section of the cornea to be presented
Topography: helpful in study of the shape of the corneal surface, or corneal curvature

Question 5

Types of Corneal Topography:

Answer 5

Placido Disk, Scheimpflug Imaging, Scanning Slit

Question 6

Placido Disk (i.e. Medmont) **following questions are on this

Answer 6

Concentric annular light source onto the corneal surface, reflected light is captured

Question 7

What type of light projects from the conical instrument?

Answer 7

Red or Infrared

Question 8

Medmont E300

Answer 8

Small cone; small red concentric circle of red lights, and used for topography data (more precise than large cone)

Question 9

Oculus Keratopgraph

Answer 9

Large Cone; less sensitive; reflection based system - measure things on tear films and tear film assessment & topography on anterior surface

Question 10

Placido Disk: Mires

Answer 10

Concentric white circles = mires = reflection on the surface of cornea

Question 11

Blurrier mires mean?

Answer 11

Evident of a poor tear film

Question 12

What would keratoconus look like with a placido disk?

Answer 12

Not symmetric and ovalish shape instead of circular shape

Question 13

On a topographer, what color is indicative of steep?

Answer 13

Hotter color = steeper + more elevated; Red is steepest

Question 14

On a topographer, what does a blue color indicate?

Answer 14

Cooler color (blue is lowest) = flatter + less elevated/or more depressed

Question 15

Scheimpflug Imaging (i.e. Pentacam) (Not under Placido Disk)

Answer 15

Off-axis light captures precise measurements of the anterior and posterior surfaces of the cornea

Question 16

Why is Oculus Pentacam significantly more $?

Answer 16

Allows for posterior measurements

Question 17

What type of anterior and posterior data does Scheimpflug give?

Answer 17

Optic scan cross section at multiple angles; can see scars, areas of thinning, if pt had keratoconus, etc…

Question 18

Scanning Slit (i.e. Orbscan)

Answer 18

Slit beams rapidly scan projected light and a camera to capture the reflected beams to create a map of the anterior and posterior corneal surface; Scheimpflug and Placido disk technology

Question 19

Analyzing a Corneal topography image

Answer 19

Refer to noteservice for images

Question 20

What do black dots mean in a corneal topography image?

Answer 20

Not reliable data in a particular area. Could be due to eyelashes covering

Question 21

Axial vs Tangential Corneal Topography?

Answer 21

Axial: Broader average of the curvature. Things are more averaged. Good for basic CL fitting
Tangential: Point by point analysis. Good for molding/finetuning/refractive sx