Aspheric Contact Lenses

Question 1

The concept of aspheric lens design has been around since

A. 1930
B. 1970
C. 1950
D. 1990

Answer 1

1950

Question 2

Why did early lens production attempts fail to produce an aspheric design?

A. Unsophisticated equipment
B. Poor lens material
C. Lack of high tech polish
D. Poor measuring equipment

Answer 2

Unsophisticated equipment

Question 3

What does the term CNC lathe mean?

A. Central numerical cut
B. Inventor’s initials
C. Computer numeric controlled
D. Cut neutralize concept

Answer 3

Computer numeric controlled

Question 4

A surface that is spherical has an eccentricity value of

A. 1.0
B. 0.0
C. 0.40
D. Greater than 0.20

Answer 4

0.0

Question 5

Which aspheric surface deviates the most from a spherical surface?

A. Ellipse
B. Hyperbola
C. Parabola
D.Circle

Answer 5

Hyperbola

Question 6

What early instrument led to a better understanding of corneal topography?

A. Keratometer
B. Zeiss slit lamp
C. Panoscope
D. Topogometer

Answer 6

Topogometer

Question 7

A parabola has an eccentricity value of

A. 1.0
B. 0.0
C. 0.40
D. Less than 0.20

Answer 7

1.0

Question 8

An ellipsodial surface has an eccentricity value of

A. 0.10 - 0.90
B. 1.0
C. 0.0
D. More than 1.0

Answer 8

0.10 - 0.90

Question 9

If the back surface apical radius of a lens is the same, what is the difference between an ellipse and a parabola?

A. The ellipse has greater asphericity
B. The parabola has a greater rate of flattening
C. The ellipse has a greater rate of flattening
D. Since the radius is the same, there is little or no difference

Answer 9

The parabola has a greater rate of flattening

Question 10

The shape of an aspheric lens is designed by its

A. E value
B. M value
C. Q value
D. Z value

Answer 10

E value

Question 11

When compared to a spherical lens, the sagittal depth of an elliptical surface with an eccentricity value of 0.45 begins to change significantly at what diameter?

A. 1.0mm - 2.0mm
B. 4.0mm - 5.0mm
C. 5.0mm - 7.0mm
D. 8.0mm - 9.0mm

Answer 11

8.0mm - 9.0mm

Question 12

How many peripheral radii can the modern CNC lathe cut?

A. 3
B. 6
C. 10
D. 18

Answer 12

10

Question 13

The advantage(s) of short polishing time is

A. Less heat generated to damage the material
B. Rapid production time
C. Alters the lathe cut surface less
D. All of the above

Answer 13

All of the Above

Question 14

The best candidate for RGP aspheric lenses has equal corneal and refractive astigmatism

A. Less than 1.00 diopter of corneal astigmatism
B. Between 0.25 and 1.00 diopter of corneal astigmatism
C. Between 2.50 and 4.00 diopters of corneal astigmatism
D. Between 0.75 and 2.50 diopters of corneal astigmatism

Answer 14

Between 0.75 and 2.50 diopters of corneal astigmatism

Question 15

Research demonstrates that the average central cornea has an eccentricity rate of

A. More than 0.70
B. Approximately 0.3
C. 0.0
D. Between 0.0 and 1.50

Answer 15

Approximately 0.3

Question 16

Research demonstrates that the average eccentricity of the mid-peripheral cornea tends to be

A. More than 1.50
B. Highly irregular and hard to measure
C. About 0.7
D. Less than 0.3

Answer 16

About 0.7

Question 17

To allow the asphericity to function, the overall diameter of the lens should be

A. 8.5mm - 9.0mm
B. 9.3mm - 10.3mm
C. 8.0mm - 9.0mm
D. Diameter has no effect on eccentricity

Answer 17

9.3mm - 10.3mm

Question 18

Then fitting a cornea with less than 0.75 D cylinder, the diagnostic base curve selection should be made based on

A. 0.20mm steeper than flat “K”
B. 0.20mm flatter than flat “K”
C. 0.10mm steeper than flat “K”
D. on “K” or slightly flatter

Answer 18

On “K” or slightly flatter