Keratometry

Question 1

Keratometer

Answer 1

Diagnostic instrument used by an eyecare specialist for measuring the curvature of the anterior surface of the cornea.

Question 2

What are the normal ranges for a keratometer?

Answer 2

43.00 to 44.00 Diopters

Question 3

What does the keratometer determine?

Answer 3

• The curvature:steepness or flatness
• Refracting power :astigmatism
• The integrity of the cornea or tear film

Question 4

When do we use a keratometer?

Answer 4

-Fitting and evaluation of CL
-Determining K readings for IOL calculation prior to cataract surgery
-Determining cause of refractive error (corneal/axial)
-Assessing change in corneal shape:
Keratoconus, corneal scarring or post surgery
-As a start point for refraction (baseline):
Evaluating distortions or irregularities

Question 5

Preparing the patient

Answer 5

1) Prepare the room
2) Focus the eye piece(to your refractive needs)
3) Position the patient
4) Occlude eye not being tested
5) Align the instrument for the patient
6) Instruct the patient to look straight ahead at the eye

Question 6

Horizontal Meridian

Answer 6

(Mouse is in center )

Question 7

Vertical meridian

Answer 7

(Mouse is in middle)

Question 8

Astigmatism: With The Rule (WTR)

Answer 8

Flattest K @ 180

Steepest curvature in the vertical meridian

Minus axis @180

K1 44.00 @180
K2 46.00 @90 ( steepest curve )

Question 9

Astigmatism: Against The Rule (ATR)

Answer 9

Flattest k @ 90

Steepest curvature In horizontal Meridian
Minus axis @90

K1 44.00 @90
K2 46.00 @180 (steepest curve)

Question 10

Simple Astigmatism

Answer 10

• simple myopic astigmatism: Plano/-2.00x180
• simple hyperopic astigmatism:
  Plano/+2.00x180

Question 11

Compound Astigmatism

Answer 11

• compound myopic astigmatism:
  - 1.00/-2.00x180
• compound hyperopic astigmatism:
  +2.00/-1.00x180

Question 12

Mixed Astigmatism

Answer 12

+1.00/-2.00x180

Question 13

What are the 5 types of astigmatism ?

Answer 13

Simple
Compound 
Mixed
Irregular 
Oblique

Question 14

What are the pros of using the keratometer?

Answer 14

Provides a clear understanding of the integrity of the pre-corneal tear film, a dynamic view of the surface of the cornea.

Question 15

Manual keratometry is preferred in patients with ?

Answer 15

Poor fixation
Corneal abnormalities
Distorted mires
Corneal dryness

Question 16

What are the cons of using a keratometer?

Answer 16

Only the astigmatic and not spherical refraction can be determined.

Does not consider astigmatism that may arise from the posterior corneal aspect and any lens.

Does not give the cylindrical lens required for correction with glasses.