The tolerance for the overall lens diamter according to the ANSI standards is: A. +/-0.005mm B. +/-0.05mm C. +/-0.01mm D. +/-0.1mm - B. According to the ANSI standards (Z80.2-1989), the tolerance for the overall diameter of a contat lens is +/-0.05mm. ANSI standards have been developed to maintain ...
NCLE Prep Exam 3 of 4 | with COMPLETE SOLUTION
The tolerance for the overall lens diamter according to the ANSI standards is:
A. +/-0.005mm
B. +/-0.05mm
C. +/-0.01mm
D. +/-0.1mm Correct Answer: B.
According to the ANSI standards (Z80.2-1989), the tolerance for the overall diameter of a contat
lens is +/-0.05mm. ANSI standards have been developed to maintain quality in the contact lens
industry. It is important to have an understanding of the ANSI guidelines.
All of the following will enable the practitioner to verify the overall rigid gas permeable lens
diameter except:
A. Slot gauge
B. Shadowgraph
C. Measuring magnifer
D. Radiuscope Correct Answer: D. Radiuscope
The slot gauge, shadowgraph and measuring magnifier will all enable the practitioner to verify
the overall lens diameter of rigid gas permeable lens. The radiuscope is an instrument that will
measure the base curve of a rigid lens.
Placing the concave side of a rigid gas permeable lens against the lens stop of the lensometer,
will provide you with which of the following?
A. Back vertex power
B. Front vertex power
C. Best vertex power
D. Closest vertex power Correct Answer: A. Back vertex power
By placing the back (posterior) surface of the rigid gas permeable lens against the lens stop, the
reading that results will be in back vertex power
An instrument that allows simultaneous verification of lens diameter, optic zone width and
peripheral curve width is:
A. Measuring magnifier
B. Ophthalmometer
C. Profile analyzer
D. Radiuscope Correct Answer: A. Measuring magnifier
An ophthalmometer, another name for the keratometer, cannot measure the listed parameters.
The profile analyzer evaluates the peripheral curve blends and the radiuscope measures the base
, curve of the rigid contact lens. The measuring magnifier is the only instrument that will measure
the parameters listed.
Assessment of the quality of the peripheral curves (blends) of a rigid contact lens is achievable
by the use of the:
A. Profile analyzer
B. Shadowgraph
C. Profile analyzer
D. Burton lamp Correct Answer: A. Profile analyzer
All of the listed instruments show that a rigid contact lens has blends. However, the only
instrument that can adequately assess the quality of the blends between the peripheral posterior
curve (PPC), intermediate posterior curve (IPC) and the central posterior curve (CPC), is the
profile analyzer.
The instrumental used for magnification of the edge of a rigid contact lens is a:
A. Keratometer
B. Shadowgraph
C. Profile analyzer
D. V-groove gauge Correct Answer: B. Shadowgraph
A keratometer measures the corneal curvature. A profile analyzer measures the peripheral curves
(blends) and a v-groove gauge measures the diameter of a rigid contact lens.
The tolerance for lens power under +/-10.00D is:
A. 0.12D
B. 0.25D
C. 0.37D
D. 0.50D Correct Answer: A. 0.12D
According to the ANSI standards (Z80.2 - 1989), the tolerance for the power of a contact lens
under +/-10.00D is +/-0.12D
Which of the following will NOT measure contact lens parameters?
A. Keratometer
B. Radiuscope
C. Burton lamp
D. Thickness gauge Correct Answer: A keratometer will measure the base curve of a lens with
an attachment known as a con-ta-check; however, a radiuscope is most frequently used. A
thickness gauge will measure the center thickness of a contact lens. A burton lamp evaluates the
fluorescein pattern similar to a slit lamp.
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