lec 16 CL physical & chemical properties

Question 1

Group 5-A is

Answer 1

Low water content, non-ionic, and surface treated lenses

Question 2

Group 5-B1 is

Answer 2

Low water content, non-ionic, non- surface treated, and hydrophilic monomer-containing lenses

Question 3

Group 5-B2 is

Answer 3

Low water content, non-ionic, non- surface treated, and semi-interpenetrating network- containing lenses

Question 4

Group 5-C is

Answer 4

High water content, non-ionic lenses

Question 5

Group 5-D is

Answer 5

Ionic materials, both low and high water

content lenses

Question 6

Low DK/t can cause what in the cornea?

Answer 6

1. Endothelial Blebs
2. Microcysts and Vacuoles
3. PH shift
4. Polymegathism
5. Fold in descemet’s membrane (5% edema = striae 10% edema = folds)

Question 7

How much oxygen is required for normal corneal metabolism for daily and month wears?

Answer 7

9. 9% for DW lenses (Dk/t = 24)

17. 9% for EW lenses (Dk/t = 87)

Question 8

What are the symptoms of soft contact lens associated corneal hypoxia (SLACH)?

Answer 8

Blurry vision 
Pain 
Tearing 
Photophobia
(Tearing & Photophobia can occur up to 8 hours after lens removal)

Question 9

Will you see neovascularization with SLACH?

Answer 9

Yes, only in extreme cases

Question 10

Lid Wiper Epitheliopathy is more common in:

Answer 10

GP & Si-Hy CL wearers

Question 11

Which dye to use when looking for Lid Wiper Epitheliopathy?

Answer 11

Lissamine Green. marx line.

Question 12

The modulus of the different CL brands.

Answer 12

Night & Day:    	1.50 
PureVision:	        1.10 
AirOptix:	                1.0 
Acuvue Oasys:       0.72 
Biofinity:	                0.8 
Acuvue True Eye:	0.71 
Dailies Total 1:	0.70 
Acuvue Advance	0.60

Question 13

What is superior epithelial arcuate lesion?

Answer 13

Mechanical friction of soft contact lens on superior cornea; excessive vaulting across superior cornea. upper lid collapse lens against cornea.
feeling of irritation and foreign body sensation

Question 14

What are the optical properties of SCL?

Answer 14

Refractive index
Spectral transmission
Dispersion
Scatter

Question 15

How does water content affect the refractive index in SCL?

Answer 15

more water contents, less refractive index

less water contents, more refractive index

Question 16

What are the material requirements for biocompatibility lens?

Answer 16

Be inert 
Contain no leachable 
Not be selectively absorbing 
Not exhibit excessive electrophoresis 
Exhibit low friction in situ
Be electrically compatible
Not induce inflammatory or immunological responses

Question 17

To ease manufacture, a contact lens material should:

Answer 17

Be homogeneous 
Have consistent mechanical properties 
Be stress-free and dimensionally stable 
Be durable and resist local heating 
Be easy to polish/retain surface finish 
Have predictable hydration characteristics

Question 18

What is the advantage of ionic material SCL?

Answer 18

more wettable

Question 19

What are the disadvantages of ionic material SCL?

Answer 19

1. Deposit more readily
2. Deposits may be bound
3. More susceptible to pH changes

Question 20

What are the advantages of non-ionic material SCL?

Answer 20

1. Less deposit prone
2. Do not bind charged particles
3. Less susceptible to pH changes

Question 21

What are the disadvantages of non-ionic material SCL?

Answer 21

less wettable

Question 22

What are the different types of tint in SCL?

Answer 22

Transparent tint: 
1. Full diameter (handling)
2. Iris diameter
3. Iris diameter, clear pupil
Prosthetic Opaque
Cosmetic Opaque

Question 23

Which is the most common SCL tint?

Answer 23

Transparent tint, iris diameter

Question 24

T/F Reactive dye is not susceptible to chorine or other bleach compounds.

Answer 24

False. it’s suceptible