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Flashcards in Lowenstein-multifocal lenses Deck (16)
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what are all fused bifocals made of



a fused bifocal is made by adding..

a glass of higher index


what index does glass exist as



what are round seg lenses limited to

22 and 24 mm


flat top segments are designated by the diameter of the circle that the seg would represent if it were complete, it sizes...

25, 28, 35, 45 mm


all plastic bifocal lenses are ______, but not all ______ lenses are plastic

one piece


what are the 2 glass one piece bifocals

ultex and exclusive


one piece bifocals are mostly made w/ a seg that has more ___________ than the main lens

plus base curve


what does an ultex consist of

very large blank w/ the base curve on the back


in which one case is the ultex design useful

produces a large round top segment w/ a very long distance from the top of the seg to the seg optical center
-this can produce a large base down prism in the seg that is not present in the dist portion of the lens


what is an executive bifocal

a one piece bifocal w/ the segment stretching across the entire lower half of the lens


where is the base curve and add in the exectuive
what about cyl

base curve is on the upper half of the lens and the add is ground onto the surface on the lower half of the lens
-cyl is ground onto the back surface and then the back surface will have 2 diff centers and radii (like all bifocals where the seg is on the front)


what is a one piece round seg bifocal
-what is the add provided by

lens made of a single plastic w the same index throughout
-add is provided by the increased radius of curvature in the seg area


how is a one piece flat top made

lens made of a single plastic w the same index throughout but w/ the top of the circle cut off


for a pt requiring an add greater than +1.75, there is often a region btwn _________________ where vision is blurred

-esp noticable when using a desk top computer


where should the intermediate power for trifocals be set for

dist of the computer or wahtever obj the pt needs to see