Lensometry and ANSI
When spotting a straight-top bifocal, the three dots should be parallel to this feature.
What is the segment line?
The primary reference point used for blocking progressive lenses is the:
What is the fitting cross?
This piece of lab equipment cuts the channel for the nylon cord or liner.
What is a lens groover?
This lens material must always be grooved wet.
What is glass?
This type of eyewear uses tension instead of compression to retain the lens.
What is nylon cord eyewear?
Unwanted vertical prism can be detected by comparing this reference point between lenses.
What is the MRP height?
Daily Double: Besides locating permanent markings, what is the second major function of a PAL identifier?
What is confirming lens design and layout information for fabrication?
A groove that is too deep weakens this part of the lens.
What is the lens edge?
This lens material can be grooved either dry or wet.
What is polycarbonate? (Trivex also acceptable)
This liner system requires a wider groove than standard nylon cord.
What is a figure-8 liner?
Daily Double: Name one ANSI tolerance related to segment placement or prism imbalance.
Acceptable answers: Vertical segment height ±1.0 mm, horizontal placement ±2.5 mm, prism imbalance limits.
Hidden circles on a PAL are located this distance from the PRP.
What is 17 mm?
The approximate groove width for standard nylon cord frames is:
What is 0.5 mm?
Wet grooving helps reduce heat and this risk.
What is chipping or cracking?
This nylon cord frame design may be found in both metal and plastic frames.
What is a recessed metal rim nylon cord system?
According to ANSI, total vertical segment height tolerance is within this many millimeters.
What is ±1.0 mm?
This chart provides fitting height, design type, and availability for a progressive lens.
What are progressive identifier charts?
Why must polishing be completed before grooving a nylon cord lens?
What is to avoid altering the groove dimensions?
Which lens material generally requires a thicker minimum edge: CR-39 or polycarbonate?
What is CR-39?
True or False: Nylon cord eyewear uses a traditional bevel to retain the lens.
False
Add power is determined by taking the difference between which two readings?
What is the distance and near sphere power?
Equal amounts of ____ prism may be used when surfacing progressive addition lenses.
What is base down?
In nylon cord eyewear, what feature replaces the function of a bevel?
What is the groove?
True or False: All lens materials use the same grooving method.
False
In nylon cord eyewear, what feature replaces the function of a bevel?
What is the groove?