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III. Contact Lenses I > Midterm I > Flashcards

Flashcards in Midterm I Deck (143)
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1

In order to steepen a GP lens, what must be done (with numbers)?

1. increase BCR by 0.50D
OR
2. increase OZD by 0.3mm

2

What type of lenticular should be used for lower plus lenses or tighter lids?

regular carrier

3

What is the upper lid position in normal lid position? 1. Lower lid? 2. What is the required GP lens fit? 3

1. 1/3 to 1/6 over cornea (10:00 and 2:00)
2. at limbus
2. lid attachment fit

4

What is the distance from the extension of the case curve edge to the surface of the lens?

radial edge lift (REL) (less than AEL)

5

If a GP lens has too much fluorescein at the edges (excessive edge width), what are the options for changing the lenses (with numbers)?

1. steepen SCR/PCR by at least 1.0mm
2. decrease SCW/PCW by at least 0.2mm

6

What are the key relationship changes to BCR and OZD to maintain the same fitting relationship (with numbers)?

1. flatten BCR (dec) 0.25D for every 0.4 to 0.5mm increase in OZD
2. steepen BCR (inc) 0.25D for every 0.4 to 0.5mm decrease in OZD

7

What is the measurement that represents the true curvature data?

tangential

8

What are sagittal depth calculations used for clinically?

1. maintaining or changing the fitting relationship
2. comparing two soft contact lenses
3. calculating center thickness of a CL

9

What are the results of using plasma of GP lenses?

1. cleaning contamination from substrates
2. improved lubricity
3. decrease in wetting angle measurements (good thing), thereby improveing on-eye wettability
4. increased bond strength

10

How would you decrease the edge lift of a lens?

steepen the peripheral curve radii and/or decrease the peripheral width

11

When were rigid gas permeable lenses first used?

1979

12

In order to flatten a GP lens, what must be done (with numbers)?

1. decrease BCR by 0.50D
OR
2. decrease OZD by 0.3mm

13

What is the typical edge thickness for unpolished lenses?

0.10 to 0.12mm

14

What are the best strategies to examine the fluorescein pattern of a GP lens?

1. use 10x or less mag
2. cobalt blue filter
3. wratten yellow filter
4. wide beam on slit lamp

15

Do myopes accommodate and converge more or less in spectacles?

less

16

What are the advantages to a lid attachment fit?

1. less movement
2. more comfortable

17

What type of prism is not able to go into contact lenses?

lateral

18

What is the typical center thickness for plano lenses?

0.20 to 0.21mm

19

What are the benefits of PMMA's?

1. readily machined
2. low cost
3. fairly wettable
4. easy to care for

20

What are the lens types that have a Dk of around 100?

1. Optimum Extra
2. Boston XO
3. Fluoroperm 151
4. HDS 100

21

What is the typical center thickness for +3.00 and up lenses?

0.30 to 0.60mm

22

What is selected to provide the appropriate power of a GP lens?

front/power curve (anterior optic zone)

23

What is the average range of horizontal visible iris diameter (HVID)?

10 to 13mm

24

What is the range of lenses that use a plano shape?

-2.00 to -3.00

25

What is the lenticular curve of a GP lens viewed with?

microscope

26

What do the peripheral curve designs provide?

1. fit cornea better
2. encourages tear exchange behind lens
3. aids in lens removal
4. assists in centration

27

What should the SCW be for a tetra-curve design? 1. ICW? 2. PCW? 3

1. 0.3
2. 0.2
3. 0.2

28

What are the different types of monomers used in GPs?

1. methacrylic acid (MA)
2. methyl methacrylate (MMA)
3. hydroxyethyl methacrylate (HEMA)
4. glycerol methacrylate (GMA)
5. vinyl pyrrolidone (VP)
6. vinyl alcohol (VA)
7. phosphorylcholine (PC)
8. siloxane

29

What is the distance from the edge of lens to extension of base curve radius (parallel to optic axis)?

axial edge lift (AEL)

30

What is the care protocol for plasma treated lenses?

1. non-abrasive cleaner
2. after 6 months can use Boston and other abrasives