Introduction to Bifocals

Question 1

Why do you need Bifocals?

Answer 1

• Presbyopia= lens becomes too stiff to move around, you can’t move the lens as much and so begin to lose accommodation
• small print becomes difficult to read, feel like they have to hold something further than arms length to read clearly
• presbyopia coincides with existing rx

Question 2

Glasses options for presbyopia

Answer 2

1) Single Vision
2) Bifocals
3) Trifocals
4) Varifocals
5) Enhanced readers/ occupationals

Question 3

Single Vision

Answer 3

• full lens dedicated to rx
• two separate pairs
• good for people doing fine work
• not convenient as they have to keep changing glasses

Question 4

Bifocals

Answer 4

Focuses at distance and near - has a visible segment

Question 5

Trifocals

Answer 5

Focuses at distance, intermediate and near

Question 6

Varifocals

Answer 6

• don’t have a visible segment
• have distance at top, near at bottom, has a smooth transition in middle for intermediate
• some distortion at the periphery

Question 7

Enhanced readers/ occupationals

Answer 7

• px doing lots of intermediate work

- more near/inter than distance

Question 8

Why pick bifocals?

Answer 8

• allow clear vision at any 2 distances
• wide reading area
• more convenient than 2 pairs

Question 9

Disadvantages of bifocals

Answer 9

• visible line bet distance vision and reading area = cosmetic
• indicative of px age
• small seg diameters have limited FOV compared with single vision
• prismatic effect - segment will also exert prismatic effect on top of main rx
• jump

Question 10

Bifocal shapes

Answer 10

Described by their segment shape and size in my eg D28

• D seg
• R seg
• C seg
• E seg

Question 11

D segs

Answer 11

• cosmetics - reasonable - straight line is noticeable tho
• vision - seg exerts base up prism - good for minus lenses as when reading, you may experience some base down prism wearing this lens
• availability - excellent, available in large and small sizes

Question 12

R segs

Answer 12

Cosmesis - good, segment not as noticeable
Vision - seg exerts base down prism so good for positive lenses
Availability- excellent, available in large and small sizes

Question 13

C segs

Answer 13

Cosmesis - better than d segs, curved top not as noticeable
Vision - seg exerts base up prism, food for minus lenses
Availability - reasonable selection of sizes

Question 14

Executive lenses

Answer 14

Cosmesis - poor - straight line across
Vision - good optics, no jump
Availability - harder to get hold of

Question 15

Advantages and disadvantages for diff segs

Answer 15

Cosmesis - r segs are less noticeable
Cost - larger segments more expensive
Availability - e segs harder to get hold of
Vision- less jumps with D segs, none with E segs