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
...
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 Dkmaterial 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:
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