peter lec Flashcards
(13 cards)
What are bifocals used for
Correction of presbyopia and are needed to replace plus power
Who developed Bifocals
Ben Franklin in 1784
what are Stock lenses
lenses that are finished and referred to uncuts
what do Progressive lenses have
Have a corridor and intermediate vision and a fitting cross
the fitting cross is usually how many mm from the corridor
4mm above
What markings do Progressive lens have
Distance verification circle, near verification circle, fitting cross, prism reference point, Datum line
Where are progressives usually measured
At the mid-pupil
Progressive lens verification have
Manufacturers engrave brand icons and add power usually on the nasal side
How do you find distance decentration
FPD-DPD
How do you find inset
DPD-NPD
How do you find the below measurement
half of B and subtract by height and you get your below
How do you find total decentration
DPD+Inset
