Chapter 5- Dispensing part II (2)

Question 1

What is the difference between bifocals and progressive lenses?

Answer 1

Progressive lenses provide the most natural vision for the wearer by seamlessly transitioning between near and far prescriptions within the lens.

Whereas, a bifocal lens is separated into distinct areas of near and far vision prescriptions

Question 2

What are the advantages of a plastic frame material?

Answer 2

1- More people are less likely to have an allergic reaction to plastic.

2- Less likely to get bent out of shape

Question 3

What are the disadvantages of a plastic frame material?

Answer 3

1- May be more breakable than a metal frame

2- Requires more frame material to make them than a metal frame so they tend to be heavier.

Question 4

What are some examples of materials that come with plastic frames?

Answer 4

1- Cellulose acetate

2- SPX

Question 5

What are the properties of cellulose acetate?

Answer 5

1- Inexpensive

2- Has reinforced sides- metal spike down the sides

3- However, they can discolour with age and can react with skin to form white deposits.

4- Adjusts at moderate heat (57 degrees)

Question 6

What are the properties of SPX?

Answer 6

1- Flexible

2- Lightweight

3- Adjusts at 95 degrees- however, it can shrink if overheated

Question 7

What are some of the materials that come with metal frames?

Answer 7

1- Nickel silver

2- Nickel titanium

3- Titanium

Question 8

What are the properties of nickel silver?

Answer 8

1- Most common metal used for frames – inexpensive

2- Can be easily adjusted

3- Skin can react to nickel

Question 9

What are the properties of nickel titanium?

Answer 9

1- Lighter than silver nickel

2- Has memory metal (returns to original shape when heated)

Question 10

What are the properties of titanium?

Answer 10

1- Expensive

2- Lighter than nickel titanium

3- Flexible

4- Hard to repair