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NCLE Advanced Certification Exam
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NCLE Advanced Certification ExamThe 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
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