National Opticianry Competency Exam -- Section I Test Questions &
Answers
When discussing thick lenses, the factors which are considered in computing the lens power
are:
a. front curve, thickness, and index
b. back curve, thickness, and index
c. front curve, back curve, and thickness
d. front curve, back curve, thickness and index - correct answer d. Front curve, back curve,
thickness and index of refraction are all factors in computing the power of a lens.
Toric transposition shows:
a. lens thickness
b. power in principal meridians
c. the power of the ADD
d. the lens diameter - correct answer b. Toric transposition shows what curves will be ground
on the lens and at what meridians.
Increasing the diameter of a minus power lens always increases its:
a. vertex power
b. center thickness
c. weight
d. refractive index - correct answer c. Increasing the diameter of any power lens will always
increase its weight.
The optical center of a round segment is located:
a. at the very top of the segment
,b. in the geometric center of the segment
c. 5 mm from the top of the segment
d. at the very bottom of the segment - correct answer b. The optical center of a round segment
is located at the geometric center of the segment.
The base curve of any multifocal lens is found on the surface containing the:
a. cross curve
b. cylinder surface
c. segment
d. ocular curve - correct answer c. The base curve of any multifocal lens is located on the same
side as the segment.
Normal slab-off (bicentric grind) is ground on the lens whose vertical meridian has the:
a. strongest curves
b. most plus power
c. least plus power
d. least minus power - correct answer c. Bicentric grinding is ground on the lens whose vertical
meridian has the weakest plus power.
The refractive error indicated by the Rx +1.75 -2.75 x090 is:
a. compound hyperopic astigmatism
b. compound myopic myopic astigmatism
c. simple myopic astigmatism
d. mixed astigmatism - correct answer d. Mixed astigmatism occurs when focus occurs in front
of the retina and also in back of the retina. A mixed power spherocylinder lens is used to
correct for this refractive power.
Tempering a lens by heat treating results in a lens being:
a. less resistant to impact
,b. more resistant to impact
c. more resistant to surface scratching
d. impossible to break - correct answer b. Heat treating makes a lens more impact resistant.
A slab-off lens is for the correction of:
a. astigmatic errors
b. excessive weight of lens
c. excessive prism imbalance at the reading level
d. exotropia - correct answer c. Excessive prism imbalance at the reading level can be corrected
by the use of slab-off lenses.
Chem-tempering makes a glass lens more impact-resistant by placing the lens in a potassium
nitrate bath. The lens undergoes a process known as:
a. ion exchange
b. iron oxide activation
c. silver halide transfer
d. thermal bleaching - correct answer a. Ion exchange occurs in chem-tempering when the
large ions of the molten bath replace the smaller ions in the glass.
Which wavelength of light have been indicated as possible contributors to the onset of
cataracts?
a. 400-520 nm
b. 520-635 nm
c. 350-400 nm
d. 635-750 nm - correct answer c. Wavelengths of 350-400 nm have been considered possible
contributors to the onset of cataracts.
When the lenses are laid out and marked for cutting and edging, the lenses are usually
decentered so as to correspond to the patient's pupillary distance after the lenses are inserted.
This is done for the following reason:
, a. to avoid unwanted prism
b. for cosmetic effect
c. to use off-center lenses
d. to avoid thick edges on the nasal side - correct answer a. The lens is decentered to
correspond to the patient's pupillary distance so the patient is looking through the optical
center of the lens, which is the point where no prism exists.
Light falling on the front surface of a spectacle lens is:
a. partially reflected, partially absorbed and the remainder refracted
b. partially reflected and the remainder refracted
c. partially absorbed and the remainder refracted
d. totally refracted - correct answer a. When light falls onto the front surface of the lens, it is
reflected, absorbed, and refracted.
A concave mirror:
a. can focus parallel incident rays to form a real image
b. can focus parallel incident rays to form a virtual image
c. always produces inverted images of real objects
d. produces virtual images smaller than the real object - correct answer a. Rays of light that
travel towards a concave mirror can focus in front of the mirror as a real image.
White light is broken into its component colors when it is :
a. diffracted
b. refracted
c. reflected
d. diffracted or refracted - correct answer d. White light breaks into its component colors
during the process of diffraction or refraction.
To the viewer; the image seen in a plane mirror appears to be:
Answers
When discussing thick lenses, the factors which are considered in computing the lens power
are:
a. front curve, thickness, and index
b. back curve, thickness, and index
c. front curve, back curve, and thickness
d. front curve, back curve, thickness and index - correct answer d. Front curve, back curve,
thickness and index of refraction are all factors in computing the power of a lens.
Toric transposition shows:
a. lens thickness
b. power in principal meridians
c. the power of the ADD
d. the lens diameter - correct answer b. Toric transposition shows what curves will be ground
on the lens and at what meridians.
Increasing the diameter of a minus power lens always increases its:
a. vertex power
b. center thickness
c. weight
d. refractive index - correct answer c. Increasing the diameter of any power lens will always
increase its weight.
The optical center of a round segment is located:
a. at the very top of the segment
,b. in the geometric center of the segment
c. 5 mm from the top of the segment
d. at the very bottom of the segment - correct answer b. The optical center of a round segment
is located at the geometric center of the segment.
The base curve of any multifocal lens is found on the surface containing the:
a. cross curve
b. cylinder surface
c. segment
d. ocular curve - correct answer c. The base curve of any multifocal lens is located on the same
side as the segment.
Normal slab-off (bicentric grind) is ground on the lens whose vertical meridian has the:
a. strongest curves
b. most plus power
c. least plus power
d. least minus power - correct answer c. Bicentric grinding is ground on the lens whose vertical
meridian has the weakest plus power.
The refractive error indicated by the Rx +1.75 -2.75 x090 is:
a. compound hyperopic astigmatism
b. compound myopic myopic astigmatism
c. simple myopic astigmatism
d. mixed astigmatism - correct answer d. Mixed astigmatism occurs when focus occurs in front
of the retina and also in back of the retina. A mixed power spherocylinder lens is used to
correct for this refractive power.
Tempering a lens by heat treating results in a lens being:
a. less resistant to impact
,b. more resistant to impact
c. more resistant to surface scratching
d. impossible to break - correct answer b. Heat treating makes a lens more impact resistant.
A slab-off lens is for the correction of:
a. astigmatic errors
b. excessive weight of lens
c. excessive prism imbalance at the reading level
d. exotropia - correct answer c. Excessive prism imbalance at the reading level can be corrected
by the use of slab-off lenses.
Chem-tempering makes a glass lens more impact-resistant by placing the lens in a potassium
nitrate bath. The lens undergoes a process known as:
a. ion exchange
b. iron oxide activation
c. silver halide transfer
d. thermal bleaching - correct answer a. Ion exchange occurs in chem-tempering when the
large ions of the molten bath replace the smaller ions in the glass.
Which wavelength of light have been indicated as possible contributors to the onset of
cataracts?
a. 400-520 nm
b. 520-635 nm
c. 350-400 nm
d. 635-750 nm - correct answer c. Wavelengths of 350-400 nm have been considered possible
contributors to the onset of cataracts.
When the lenses are laid out and marked for cutting and edging, the lenses are usually
decentered so as to correspond to the patient's pupillary distance after the lenses are inserted.
This is done for the following reason:
, a. to avoid unwanted prism
b. for cosmetic effect
c. to use off-center lenses
d. to avoid thick edges on the nasal side - correct answer a. The lens is decentered to
correspond to the patient's pupillary distance so the patient is looking through the optical
center of the lens, which is the point where no prism exists.
Light falling on the front surface of a spectacle lens is:
a. partially reflected, partially absorbed and the remainder refracted
b. partially reflected and the remainder refracted
c. partially absorbed and the remainder refracted
d. totally refracted - correct answer a. When light falls onto the front surface of the lens, it is
reflected, absorbed, and refracted.
A concave mirror:
a. can focus parallel incident rays to form a real image
b. can focus parallel incident rays to form a virtual image
c. always produces inverted images of real objects
d. produces virtual images smaller than the real object - correct answer a. Rays of light that
travel towards a concave mirror can focus in front of the mirror as a real image.
White light is broken into its component colors when it is :
a. diffracted
b. refracted
c. reflected
d. diffracted or refracted - correct answer d. White light breaks into its component colors
during the process of diffraction or refraction.
To the viewer; the image seen in a plane mirror appears to be:
