Unit 3

Question 1

P=(n-1)/r where:

Answer 1

P= curvature power in diopters
n= 1.3375 (index of refraction for eyes
r= radius of curvature IN METERS

Question 2

Average corneal power

Answer 2

43.50 D

Question 3

Steeper cornea is higher or lower diopter value

Answer 3

Higher

Question 4

Flatter cornea is higher or lower diopter value

Answer 4

Lower

Question 5

With the rule astigmatism Is steeper at what axis?

Answer 5

90 degree (vertical axis)

Question 6

Against the rule astigmatism is steeper at what axis?

Answer 6

180 degrees (horizontal)

Question 7

What kind of astigmatism looks like a red eight

Answer 7

With the rule

Question 8

What kind of a stigmatism looks like a red Bow tie

Answer 8

Against the rule

Question 9

Purposes of keratometry

Answer 9

-Detect amount and type of astigmatism
-Determine initial contact lens shape
-Intraocular lens implant selection
-Indicate a compromised cornea
-Diagnose keratoconus
-Assess tear layer and quality

Question 10

Radius of curvature should be written in this unit of measure

Answer 10

Metres

Question 11

As the radius of corneal curvature gets bigger the K reading does this

Answer 11

Gets smaller

Question 12

What does MCAR stand for

Answer 12

Mires clear and regular

Question 13

What does corneal topography do

Answer 13

Describes the shape of the corneal surface and all meridians

Question 14

In topography normal corneas are represented by these colours

Answer 14

Greens and yellows

Question 15

In topography flatter areas are represented by these colours

Answer 15

Blues or cool colours

Question 16

In topography steep areas are represented by these colours

Answer 16

Reds or hot colours

Question 17

All corneal topography devices display this information

Answer 17

-Keratometry values
-Power and access of the flattest meridian

Question 18

Purposes of corneal topography

Answer 18

-Screen for corneal changes
-Monitor corneal ectasia
-Fitting contact lenses
-Pre-and post refractive surgery
-Post keratoplasty
-Ocular surface disorders

Question 19

What does a placido disc do

Answer 19

Determines the shape of the anterior cornea only

Question 20

What does slit scanning and Scheimpflug technology do

Answer 20

Take a series of 2-D images and reconstruct them into 3-D image of the front and back surface of cornea

Question 21

Axial maps are good for this

Answer 21

-Corneal power
-Good overview

Question 22

Tangential maps are good for this

Answer 22

-Power and curvature at individual points
-Most accurate

Question 23

Elevation maps

Answer 23

Placido- calculate elevation
Scheimpflug- Actual elevation measured

Question 24

Corneal thickness map is taken by these machines

Answer 24

-Scheimpflug
-scanning slit

Question 25

Review manual keratometer labelling answer key

Answer 25

Try to name the parts based only on the numbers