Intro to CLs

Question 1

Previous GP indication for soft CLs

Answer 1

Previous GP adherence & 3 and 9 oclock staining

Question 2

CI for soft CLs

Answer 2

• Inflammation/ disease of AS
• Poor hygiene
• Chronic allergies/antihistamine used
• Systemic/Autoimmune/ immuno compromised diseases
• poor tear film
• irregular astigmatism
• Radial keratomy
• Dry/dusty enviroments
• giant papillary conjuctivitis

Question 3

Rigid lenses include 2 types

Answer 3

PMMA and GP

Question 4

Why are PMMA hardly used?

Answer 4

Rigid lenses with NO OXYGEN TRANSFER

Question 5

What are GP made of?
How is the oxygen transfer?
Where do they sit in respect to the cornea?

Answer 5

Made of acrylic, silicone, flourine
Allows oxygen transfer but less than soft CLs
Sits ON the cornea

Question 6

Soft CLS are made of ____.
How is their oxygen transfer?
Where do they sit in respect to the cornea?

Answer 6

Made of plastic polymer and water
Water allows the passage of Oxygen
Larger than cornea sits past the limbus

Question 7

“Ideal CL fit”
Rigid lenses:
Soft CLs:

Answer 7

The lens to parallel the corneal shape for rigid

The lens to drape evenly for soft CLS

Question 8

Lens will shift in a part of the cornea is too

Answer 8

Flat

Question 9

What is a BC?

Answer 9

How steep or flat the center portion of the lens is

Usually same a corneal center

Question 10

Soft lens fitting measurements

Answer 10

Focused on BC

Question 11

Rigid lens fitting measurements

Answer 11

Focused on BC, secondary & tertiary curve

In order for a rigid lens to parallel the corneal shape, it must flatten in periphery as well

Question 12

What are secondary and tertiary curves

Answer 12

Gradually flatten towards the edge

Numbers get larger BC-> SC->TC

Question 13

How does a GP lens look and why?

Answer 13

Starts a bit steep toward the center and flatten as you go out to allow room for tears to move underneath the lens

Question 14

The edge lift in a rigid lens allows tear exchange. This is important because it allows:

Answer 14

• Lens to move a bit
• Nutrients to get to the cornea
• Not having the tear film present would erode corneal
• Problems if too steep or edge is curved in

Question 15

Multiple reasons why rigid lenses need the edge lift:

Answer 15

Tear exchange
Enhaced capillary attraction
Prevent erosion of cornea or epithelium

Question 16

For the edge lift in rigid lenses the PC should be

Answer 16

A little flatter than the radius of curvature of the cornea in that area

Question 17

Equation for effective power?

Answer 17

F2= F1/(1-dF1)

d= 12mm

Question 18

Clinically, you should vertex any power that’s ___

Answer 18

4.00D and above. Anythig less, the change would be less tham 0.25 so insignificant

Question 19

Minus lens are ___ effective when moved closer to the eye.

Will need ___ power in CL than specs

Answer 19

More effective

Less power in CL

Question 20

Plus lens are ___ effective when moved closer to the eye.

Will need ___ power in CL than specs

Answer 20

Less effective

More power

Question 21

How does vertex distance effect accommodation stimulus?

Myopes vs hyperopes

Answer 21

Myopes acc. Increased as lens is move towards the eye

Hyperopes acc decreases as lens is move towards the eye

Question 22

Presbyopes response after CLs?

Myopes vs hyperopes

Answer 22

Myopes would notive NVA are affected in CL before glasses (woll need bifocals sooner bc of acc. Stimulus )

Hyperopes may be able to push it off for a bit longer in CLs than in glasses

Question 23

_____ children with ___ AC/A ration should be encouraged to consider CLs.

Answer 23

Hyperopic with high AC/A ratios

Ortho at far and eso at near

Question 24

Retinal image size is dependent on

Answer 24

Lens power and distance from the eye

Question 25

Maginifcation/minifications with CLs?

Myopes vs hyperopes

Answer 25

Myopes will have less minification : appear larger

Hyperopes will have less magnification: appear smaller

Question 26

Always do a binocular assesment before prescribing CLs because

Answer 26

Patients who need a lot of prism or BU wil still need glasses becuse it’s the only way to prescrive it

With fragile binocularity and acc. Function, problems can occur