Multifocal Lenses

Question 1

widest section of the segment area prior to edging, often part is cut off

Answer 1

seg width

Question 2

seg depth vs seg height

Answer 2

depth is in uncut blank

height is in lens cut to fit frame

Question 3

vertical distance from DRP to top of seg

Answer 3

seg drop

Question 4

distance that the lens must be decentered from GC to correspond with OC

Answer 4

inset

Question 5

amount the seg must be further decentered to correspond with the near PD

Answer 5

seg inset

Question 6

total inset=

Answer 6

inset+seg inset

Question 7

multifocal construction where no ledge or change of curvature on the front surface can be felt, it’s only available with glass (2 materials), having a higher index than the carrier lens

Answer 7

fused

Question 8

multifocal construction where only one material is used, power change occurs due to change in surface curvature, you can feel the segment, all plastic-like materials are made of this design

Answer 8

one piece

Question 9

multifocal construction where custom small segments are glued onto the carrier lens, usually a round small segment

Answer 9

cemented lens

Question 10

multifocal construction where two sections are glued together as upper and lower type, near OC can be displaced from distance OC

Answer 10

franklin construction

Question 11

franklin construction is only used for creating _

Answer 11

horizontal prism in the near portion

Question 12

most commonly used non-PAL type of multifocal

Answer 12

D segments with OC 5 mm below seg

Question 13

D-_ is most common
What is the range?
seg drops range from?

Answer 13

28
25-45
2mm to 7mm

Question 14

round segs vary in size: _
main advantage:
a main use:
seg drop:

Answer 14

22mm to 40 mm (smaller available for occupational)
very unnoticeable
therapeutic lens for children
4 mm to 9mm

Question 15

a _ is a round seg that tapers off into the distance portion

blur zone:

Answer 15

blended seg

2-3mm

Question 16

difference between B and R ribbon segments?

Answer 16

OC is at center of B, OC can be moved up and down for R

Question 17

ribbon segs are used for what occupations?

Answer 17

bricklayers and heavy equipment operators

Question 18

B ribbon segs allow for _

Answer 18

distance vision below the segment

Question 19

curve top segs (like D) sizes vary:

OC is _mm below top

Answer 19

22-28mm

4.5mm

Question 20

executive lens is similar to franklin, but only one-piece and distance and near OCs are _

Answer 20

coincident

Question 21

main advantage of executive lens

Answer 21

maximum reading zone

Question 22

disadvantages of executive?
ledge increases as _ increases
thickness is dependent on _
_ than D-segs
large ED should be avoided

Answer 22

add power
near power
thicker/heavier

Question 23

ultex: round seg with _ diameter

where is near OC?

Answer 23

very large

bottom of blank, may be cut off with edging

Question 24

trifocals are typically _% of add power

trifocals are not available with near add powers of less than _

Answer 24

50

+1.50

Question 25

7x28 trifocal means:

Answer 25

7mm height, 28mm width

Question 26

flat top trifocal is typically a _

executive trifocal spans _

Answer 26

D-seg

width of lens

Question 27

E/D trifocal is _

used for which type of work?

Answer 27

executive intermediate, D-25 near

office desk work, largest intermediate possible

Question 28

occupational segs are double round _ _ or _mm
seg separations are _mm
are dissimilar adds available?

Answer 28

22, 25, 28
14
yes

Question 29

a quadrafocal is a double round occupational lens with a _

Answer 29

trifocal on bottom seg

Question 30

golfer’s classic:
_mm round seg
_ add
_ seg drop

Answer 30

15mm
low
10mm

Question 31

High DefAmberd High Contrast Orange
28mm wide _
_mm seg drop
good for who?

Answer 31

flat top
7
outdoor enthusiasts

Question 32

in flat top bifocal, seg line should coincide with _

Answer 32

lower lid

Question 33

when fitting trifocals, top of intermediate zone should coincide with _

Answer 33

bottom of the pupil

Question 34

if a patient is erect with head up, fit _

Answer 34

lower

Question 35

if a patient is slouched with chin down, fit _

Answer 35

higher (already looking down)

Question 36

height:
tall patients?
short patients?

Answer 36

lower segs - need to turn eyes downward more

don’t raise for short patients

Question 37

fit round segs slightly _

Answer 37

higher (1mm) because top of seg is useless

Question 38

blended bifocals should be fit 1mm _, be aware of blur zone

Answer 38

higher

Question 39

for high powered distance rxs, fit BF a little _

and put OC a little _

Answer 39

higher

higher

Question 40

if seg is too high, _ vertex distance

if seg is too low, _ vertex distance

Answer 40

decrease

increase

Question 41

to compensate for seg height difference due to different size frames

1) determine difference in A dimension
2) divide by 2
3) add to measured seg height

Answer 41

-