NCLE Advanced Certification Exam with COMPLETE SOLUTION | 459
Questions with 100% Correct Answers
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
14. Which is not an indication for modifying a rigid gas permeable lens?
A. Corneal staining
B. Poor lens position
C. Discomfort
D. Surface Wettability Correct Answer: The answer is D.
Questions with 100% Correct Answers
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
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 Correct Answer: 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.
14. Which is not an indication for modifying a rigid gas permeable lens?
A. Corneal staining
B. Poor lens position
C. Discomfort
D. Surface Wettability Correct Answer: The answer is D.
