Chapter 9 Flashcards
In the making of concentric style bifocals, the different power zones (distance and near) may be ground on:
a) the front surface b) the back surface
c) either surface d) both surfaces
either surfaces
The addition of fluorine to the rigid lens ingredients increases:
wettability
Which of the following instruments would NOT be used to verify the lens diameter in the office?
a) diameter gauge b) radiuscope
c) measuring magnifier d) projection magnifier
Radiuscope
Mounting the lens blank in the lathe so that the face of the button is perpendicular to the spindle is necessary to avoid:
unwanted prism
When reading the radius of curvature of the back surface with the radiuscope, the lens is floated on a drop of liquid to:
a) neutralize the reflection from the front surface
b) keep the front surface clean
c) level the lens
d) none of the above
a) neutralize the reflection from the front surface
During the lathing process for toric lenses, cylinder power is generated by:
Squeezing the lens in a crimping tool
When the lens power is verified, placing the concave surface against the lensometer aperture will reveal ______ power.
Back vertex
Which of the following polishes should NOT be used to polish gas permeable lenses?
a) Silvo b) Sil-02-Care c) Alox d) X-Pal
a) Silvo
After reducing the overall diameter, which of the following additional modifications are required?
a) applying peripheral curves b) blending
c) edge shaping and polishing d) all of the above
d) all of the above
Removal of plastic from the bottom of a lens to produce a flat edge that will control rotation is called: a) prism ballast b) truncation
c) base curve d) blending
b) truncation
In-office power changes should be limited to ± __ D. or less.
a) 0.25 b) 0.50 c) 1.00 d) 2.00
b) 0.50
When rigid lenses are manufactured, which parameter is cut first?
a) anterior convex curve
b) central posterior curve
c) CN bevel
d) posterior peripheral curve
b) central posterior curve
After the sharp junctures between curves on the lens posterior are smoothed out, they are called:
a) blends c) lenticulation b) bevels d) apex
a) blends
Which in-office modification is the easiest to perform?
a) changing base curve
b) adding plus power
c) truncation
d) adding minus power
d) adding minus power
Calculation of which lens parameter is NOT under the control of the fitter?
a) central posterior curve
b) posterior optical zone
c) anterior power curve
d) center thickness
a) centeral posterior curve
Polishing the surfaces of rigid gas permeable lenses should be performed:
a) every six months
b) only when it is needed
c) every year
d) never
b) only when it is needed
Lens blends and “ski edge” can be verified using a:
a) keratometer
b) junctometer
c) radiuscope
d) long fluorescent light bulb
d) long fluorescent light bulb
An in-office modification that can be done to thin the edge of a minus lens is the:
a) hyperflange b) myoflange
c) CN bevel d) ski edge
c) CN bevel
The ideal finished edge thickness for rigid lenses, regardless of whether they are plus or minus, is____mm a) 0.08-0.12 b) 0.04-0.10 c) 0.20-0.44 d) 0.5-1.0
a) 0.08-0.12
In aspheric lens design, the change in curvature that occurs from the center to the edge of the aspheric zone is called:
eccentricity
Hydrogel lens materials allow the transport of oxygen to the cornea and carbon dioxide away from the cornea because they contain:
three dimensional polymers
The FDA has created four lens groups to clarify categories of similar hydrophilic lens polymers. These groups are defined by:
water content and electrostatic properties
During the lathe cutting process, humidity must be controlled at a low level in order to:
a) avoid premature hydration
b) maintain quality standards
c) avoid destruction of the lens
d) all of the above
d) all of the above
A spin cast lens will generate:
an aspheric back surface
