nao volume II Exam 100% Accurate!!
ED - ANSWERSEffective diameter. Twice the longest radius. Used to determine the smallest lens blank
that needs to be cut.
B - ANSWERSThe vertical box dimension or the vertical distance between two horizontal tangents to the
vertical extremities of the lens shape.
DBL - ANSWERSDistance between lenses
DBC - ANSWERSDistance between centers. See GC. Frame PD
GC - ANSWERSThe geometric center of the box, eyewire, or lens shape
OC - ANSWERSOptical center. Point of not prism
Why did the FDA ban cellulose nitrate as a frame material? - ANSWERSIt was too flammable to be
considered safe
When were lenses first set in frames? - ANSWERSLate in the 13th century
Who were the first spectacle makers? - ANSWERSGoldsmiths
Which of the following frame materials was not used until the 20th century? - ANSWERSStainless steal
Why is plastic a popular material for spectacle frames? - ANSWERSIt can easily be molded and shaped.
What special care is required for nylon frames? - ANSWERSPeriodic soaking in water overnight
ED - ANSWERSEffective diameter. Twice the longest radius. Used to determine the smallest lens blank
that needs to be cut.
B - ANSWERSThe vertical box dimension or the vertical distance between two horizontal tangents to the
vertical extremities of the lens shape.
DBL - ANSWERSDistance between lenses
DBC - ANSWERSDistance between centers. See GC. Frame PD
GC - ANSWERSThe geometric center of the box, eyewire, or lens shape
OC - ANSWERSOptical center. Point of not prism
Why did the FDA ban cellulose nitrate as a frame material? - ANSWERSIt was too flammable to be
considered safe
When were lenses first set in frames? - ANSWERSLate in the 13th century
Who were the first spectacle makers? - ANSWERSGoldsmiths
Which of the following frame materials was not used until the 20th century? - ANSWERSStainless steal
Why is plastic a popular material for spectacle frames? - ANSWERSIt can easily be molded and shaped.
What special care is required for nylon frames? - ANSWERSPeriodic soaking in water overnight
