Keratometry

Question 1

is an instrument used to measure the front surface curvature of the cornea

Answer 1

Keratometer

Question 2

the approximate radius of cornea

Answer 2

3 mm

Question 3

Informations that keratometer provide:

Answer 3

The radii of the curvature of the cornea
The degree of corneal astigmatism
Presence of corneal distortion
Direction of the principal meridian of the eye

Question 4

Keratometry is essential in the

Answer 4

fitting of CL, evaluating patients with keratoconus, and IOP implant surgery

Question 5

Refractive index of cornea

Answer 5

1.3375

Question 6

Parts of keratometer

Question 7

One position keratometer: measures 2 meridian at the same time

Answer 7

Bausch and Lomb Keratometer

Question 8

Two position keratometer: measures one meridian at one time

Answer 8

Javal-Schiotz Keratometer

Question 9

Note: difference between one position keratometer and two position is that Bausch and Lomb Ker has circles while Javal-Schiotz has rectangles and stairs

Question 10

When the weakest corneal meridian is at near 180

Answer 10

WTR

Question 11

When the weakest corneal meridian is at 90

Answer 11

ATR

Question 12

If the principal meridian are between 30 and 60 degrees or between 120 and 150 degrees

Answer 12

Oblique

Question 13

It determines the relationship between corneal and refractive astigmatism

Answer 13

Javal’s Rule

Question 14

Types of astigmatism

Answer 14

Simple astigmatism
Compound astigmatism
Mixed Astigmatism
Irregular Astigmatism
Oblique Astigmatism

Question 15

one focal line falls on the retina, the other meridian may fall in front or behind the retina

Answer 15

Simple astigmatism

Question 16

Both focal points lie either in front or behind the retina

Answer 16

Compound Astigmatism

Question 17

one focal point lies behind the retina, the other focal point lies in front of the retina

Answer 17

Mixed Astigmatism

Question 18

the flat and steep axes are not at right angles

Answer 18

Irregular Astigmatism

Question 19

occurs along the 45 degrees or 135 degrees meridians

Answer 19

Oblique Astigmatism

Question 20

WTR Astigmatism has ___ steepest curvature

Answer 20

Vertical

Question 21

ATR Astigmatism has ______ steepest curvature

Answer 21

Horizontal

Question 22

Manual keratometry is preferred in patients:

Answer 22

with poor fixation
Corneal abnormalities
distorted mires
when cornea is highly toric
cornea is dry

Question 23

Preferred in px with readings less than 40 D or greater than 46 D

Answer 23

Corneal topography

Question 24

used to verify no corneal abnormalities and astigmatism is regular

Answer 24

Topography

Question 25

Determines the axis and magnitude of corneal astigmatism

Answer 25

Toric calculator

Question 26

A degenerative corneal disease resulting in a generalized thinning and cone-shaped protrusion of the central cornea

Answer 26

Keratoconus

Question 27

Mild keratoconus

Answer 27

45D

Question 28

Moderate keratoconus

Answer 28

45-52D

Question 29

Advanced keratoconus

Answer 29

52D

Question 30

Severe keratoconus

Answer 30

62D

Question 31

Vertical misalignment of plus signs indicates

Answer 31

Astigmatism

Question 32

Bausch and Lomb contains how many prisms

Answer 32

2 prisms

Question 33

Procedure in using kera

Question 34

Determined by retinoscopy or subjective refraction

Answer 34

Refractive Astigmatism

Question 35

Due to the toricity of the back surface of the cornea and tilting of the crystalline lens with respect to the optic axis

Answer 35

Internal astigmatism

Question 36

Correct axis alignment when the horizontal lines of the plus appear

Answer 36

Continuous

Question 37

Corneal abnormalities

Answer 37

• Irregular contour or shape of cornea •Inadequate or excessive tear film •Ointment on the cornea •Eyelid interference

Question 38

first to use the doubling principle

Answer 38

Helmholtz

Question 39

What did Helmholtz used

Answer 39

two small glass plates with plane parallel faces

Question 40

Javal Schiotz used what type of doubling prism

Answer 40

Wollaston prism as a doubling device.

Question 41

Chamber-inskeep ophthalmometer used what doubling prism

Answer 41

Biprism

Question 42

Clinical Use of Keratometric Information

Answer 42

■ CL fitting, choice of trial lens ■ Monitoring corneal shape ■ Verification of contact lens parameters ■ Measure corneal power