Dispensing 4 - Occupational lenses Flashcards
What is an occupational lens?
a lens that is chosen for a specialised viewing situation so not for general wear
what kind of occupations may wear double segment lenses?
-plumbers
-electricians
-mechanics
-pharmacists
-librarians
what are double segment/ double d lenses?
-occupational lenses that provide intermediate vision when looking up instead of bifocals/trifocals where you have to look down
-they are also known as multifocal lenses
what is a quadrifocal lens?
a trifocal lens with upside down segment at the top
how wide are double d style double segment lenses?
28mm
Whats the minimum separation of
double round segment lenses
4mm?
whats the typical segment separation in double segment lenses?
14mm
what kind of people may typical progressive lenses not be good for? What other lenses would also not be appropriate for these people and why?
may not be good for those whose visual tasks are predominantly based around near or intermediate work such as:
-office workers
-cooks
-decorators
-people who play card/ board games
-people who read sheet music
other lenses not good for this are:
▪ ordinary reading lenses may not give enough depth of vision
▪ bifocals will miss the intermediate area altogether
▪ trifocals may not have large enough areas
whats the main limitation of varifocal lenses?
distance portion lies straight ahead so if the px does lots of intermediate tasks like heavy computer use, the px will keep having to lift their chin up or lift frames to see intermediate which gets tiring doing it all day
whats the difference between a typical degressive lens and a typical progressive lens?
in a degressive lens, you take the near as reference and remove plus to get the intermediate while for a typical progressive, you take the distance Rx is the reference and progressively add plus power
What is an example of a degressive lens and what is the fitting like?
Essilor Interview of -0.80D or -1.30D degression
fitting is at the lower limbus with respect to HCL
what are restricted distance lenses?
Similar to a degressive but with ‘distance’ portion at the very top of lens
Give an example of a restricted distance lens
Varilux computer V3:
▪ Semi Distance Zone
▪ Power in the semi-distance zone can correspond to the distance prescription or can be over plussed by 0.25D or 0.50D
How do restricted distance lenses work?
allow for a narrow area of distance vision in the very top of the lens, allowing the wearer to see across an office or meeting room, whilst providing a
wider area for near and intermediate vision than a traditional varifocal would give
what are restricted distance lenses for?
for providing patients with even more depth of vision than other vocational lenses
