NCLE Advanced Certification Exam

NCLE Advanced Certification Exam

NCLE Advanced Certification Exam

The answer is D.

The posterior optical zone will directly affect the lens to cornea relationship of a rigid gas

permeable lens. If the posterior optical zone is steepened, it will increase the sagittal depth. If it

is flattened, it will decrease the sagittal depth. Changing the power, which is accomplished by

changing the anterior optical zone, will not affect the sagittal depth of the lens, nor will changing

its edge design. - ✔✔1. The sagittal depth of a rigid gas permeable contact lens can be altered

without changing the diameter by:

A. Changing the power

B. Changing the edge design

C. Changing the radius of curvature of the anterior optical zone

D. Changing the radius of curvature of the posterior optical zone

The answer is A.

A lens is truncated by removing a segment of the lower edge of a contact lens. This creates a

straight edge that interacts with the lower lid and aids in lens positioning. Of the lens designs

listed in the question, the only one that requires precise positioning of its optical portions is a

translating bifocal lens. - ✔✔2. A truncation is used on a rigid gas permeable contact lens to help

enhance the performance of which type of design?

A. Bifocal

B. Aphakic

C. Bitoric

D. Keratoconus

The answer is B.

A lenticular or myoflange design will decrease the mass of an aphakic lens as well as increase

the edge profile, which allows it to interact more with the upper lid and aid in positioning of the

lens. - ✔✔3. The mass of an aphakic rigid gas permeable contact lens can be reduced by making

the lens design:

A. Spherical

B. Lenticular

C. Tricurve

D. Aspheric

The answer is B.

Increasing the optical zone diameter and increasing the overall lens diameter will both tighten

and steepen the relationship of the lens to the cornea. Decreasing the optic zone diameter will

serve to flatten and loosen the lens to cornea relationship. Using a prism-ballasted lens design

will not affect the lens to cornea relationship as it relates to sagittal depth. - ✔✔4. In order to

tighten the fit of a rigid gas permeable lens you can:

I. Increase the optical zone diameter

2. Decrease the optical zone diameter

3. Increase the overall lens diameter

4. Use a prism ballasted lens design

A. 3 only

B. 1&3

C. 2 only

D. 2&3

The answer is D.

A hyperflange will decrease edge thickness as well as lens awareness . Aspheric peripheral

curves change the posterior design of the lens but do not reduce edge thickness. A higher Dk

material will not change the overall lens edge thickness. A myoflange will actually add thickness

to the lens edge and is used for high plus lenses not high minus lenses. - ✔✔5. A high minus

rigid gas permeable lens will be thin centrally with relatively thick edges. To reduce the edge

thickness, and increase overall comfort, use:

A. Aspheric peripheral curves

B. A myoflange

C. A higher Dk material

D. A hyperflange

The answer is C.

One would rarely polish or attempt to manipulate the central posterior surface of a rigid lens.

Applying polishing pressure to the mid-peripheral and the peripheral anterior surface would add

plus power. Applying polishing pressure to the central anterior surface would add minus power. -

✔✔6. To add minus power to a rigid contact lens with a rotating modifying spindle, one would:

A. Polish the posterior surface of the rigid lens

B. Polish the mid peripheral anterior surface

C. Polish the central anterior surface

D. Polish the peripheral anterior surface

The answer is A.

The keratometer readings indicate the need for a spherical back surface, which would rule out the

use of a bitoric lens. A soft spherical lens would not correct the moderate amount of refractive

astigmatism that is present, nor would the spherical rigid gas permeable lens. A front surface

toric RGP would best meet this patient's needs since it has a spherical back surface, but has a

toric front surface which would correct the residual astigmatism. - ✔✔7. Which lens design

would provide the best visual acuity for a patient with the following information?

K's 42.00@ 180/ 42.50@90

Rx -6.75 +1.75 cx 90

A. Front surface toric rigid gas permeable

B. Spherical rigid gas permeable

C. Soft sphere

D. Bitoric rigid gas permeable

The answer is A.

The wetting angle of a rigid gas permeable material describes how a fluid spreads over the

surface. It is important to remember, however, that wetting angle is a description of the material

outside of the patient's natural ocular environment. Within minutes of insertion, a rigid lens is

encapsulated in the natural tear mucin and the wetting angle of the material is no longer

important. - ✔✔8. Which of the following describes the angle that the edge of a bead of water

makes with the surface of a plastic?

A. Wetting angle

B. Surface angle

C. Bead angle

D. Reflection angle

The answer is B.

The back surface of a rigid lens will usually correct only the astigmatism that is found on the

surface of the cornea. Therefore, when there is significantly more astigmatism in the refraction

than on the surface of the cornea, residual astigmatism is anticipated. - ✔✔9. If a patient has 1.50

D of refractive cylinder and keratometer readings of 44.00@ 180/ 44 .50 @ 90, a spherical rigid

gas permeable lens will:

A. Give the patient their best correctable vision

B. Usually result in residual astigmatism

C. Fit poorly

D. Be uncomfortable

The answer is C.

Lenticular astigmatism usually exists when the amount of refractive cylinder is greater than the

amount of corneal cylinder. It is assumed that the additional astigmatism originates in the

crystalline lens. - ✔✔10. If a patient has spherical K readings of 43.50 and an Rx of -4.00 +1.75

cx 90, the patient has:

A. Corneal astigmatism

B. Against the rule astigmatism

C. Lenticular astigmatism

D. Mixed astigmatism

The answer is B.

With regular astigmatism, even high degrees, a soft toric lens can work quite effectively.

Presbyopic and aphakic patients can also be successfully fit with soft lenses. However, patients

with irregular astigmatism will achieve their best visual acuity only with rigid gas permeable

lenses since soft lenses will mold to the corneal contour and not mask the irregularity. - ✔✔11.

In which of the following situations is a rigid gas permeable lens always preferred over a soft

lens?

A. Regular astigmatism

B. Irregular astigmatism

C. Aphakia

D. Presbyopia

The answer is A.

Decreasing the optical zone diameter while steepening the base curve of a rigid gas permeable

lens will allow the lens to cornea relationship to remain the same, since decreasing the optical

zone diameter loosens the lens to cornea relationship and steepen- ing the base curve tightens the

relationship. Increasing the overall lens diameter also tightens the fit and will only exaggerate the

change made to the lens to cornea relationship. Decreasing the center thickness or increasing the

lens power will have no significant effect on the relationship of the lens to the cornea. - ✔✔12.

In order to steepen the base curve of a rigid gas permeable lens without changing the lens to

cornea relationship, you would also need to:

A. Decrease the optical zone diameter

B. Decrease the center thickness

C. Increase the overall lens diameter

D. Increase the lens power

The answer is B.

Increasing the overall lens diameter or increasing the optical zone diameter will steepen the lens

to cornea relationship. Conversely, decreasing the optical zone diameter, decreasing the overall

lens diameter or flattening the base curve will loosen the relationship. If one change is made that

tightens the relationship and another is made that loosens it, the changes will cancel each other

out. - ✔✔13. To steepen the lens to cornea relationship of a rigid gas permeable lens you could :

A. Increase overall diameter and decrease optical zone diameter

B. Increase overall diameter and increase optical zone diameter

C. Increase optical zone diameter and decrease overall diameter

D. Increase optical zone diameter and flatten base curve

The answer is D.

Modification of rigid gas permeable lenses is a valuable skill and can increase a practitioner's

success at RGP fitting. Many in-office modifications can be utilized to improve the positioning

of a lens, reduce discomfort for the patient and eliminate corneal staining. - ✔✔14. Which is not

an indication for modifying a rigid gas permeable lens? 

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Version 2022
Category Exam (elaborations)
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Authors qwivy.com
Pages 161
Language English
Tags NCLE Advanced Certification Exam
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