NCLE Advanced Certification Exam With Correct Answers
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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 a...
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NCLE Advanced Certification Exam
With Correct Answers
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. - Answer 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. - Answer 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. - Answer 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
,NCLE Advanced Certification Exam
With Correct Answers
relates to sagittal depth. - Answer 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. - Answer 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. - Answer 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
,NCLE Advanced Certification Exam
With Correct Answers
correct the residual astigmatism. - Answer 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. - Answer 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. - Answer 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. - Answer 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
, NCLE Advanced Certification Exam
With Correct Answers
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. - Answer 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. - Answer
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. - Answer 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.
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