8. How to: Lens selection

Question 1

Can you select a lens for a patient?

Answer 1

You can never decide, you can offer the options available and allow the Px to make a choice

Question 2

True or false- soft hydrogel lenses moulds to the shape of the cornea?

Answer 2

True

Question 3

Which lenses are bigger or smaller compared to the cornea- Soft CL or RGPs?

Answer 3

Soft hydrogel lenses: Larger then cornea
RGP: Smaller then cornea

Question 4

How are RGP lenses designed?

Answer 4

To match the profile of the cornea

Question 5

2 reasons why RGP lenses not that common?

Answer 5

1. They are not comfortable- takes 2 weeks for the cornea to desensitize and build up on the wearing time.
2. They are ordered on exchange: patients need to come back to get the perfect fitting.

Question 6

FT meaning

Answer 6

Full time

Question 7

Is it a concern if Px with orthokeratology lens are wearing them overnight?

Answer 7

No

Question 8

EW meaning

Answer 8

Extended wear

Question 9

If wearing lenses more then 3 times a week, what option is cheaper- monthly or daily lenses?

Answer 9

Monthly lenses cheaper in this case.

Question 10

Meaning of SV?

Answer 10

Single Vision

Question 11

Meaning of MF

Answer 11

Multifocal

Question 12

Can you have prism into CL?

Answer 12

No

Question 13

What is a soft CL?

Answer 13

Plastic which contains varying amount of water.

Question 14

What does it mean when a materials name ends with “filcon”?

Answer 14

This is a material used for soft CL

Question 15

HT Meaning on lenses?

Answer 15

Handling tint- bluish hue on lenses

Question 16

Base curve relates to?

Answer 16

Curvature of the back surface

Question 17

TD- Total diameter relates to?

Answer 17

This is the overall size of the lens

Question 18

Why do silicone lens have a lower water content?

Answer 18

Because they have silicone that transports much more oxygen and hence, a lower content of water is required. This also reduces dehydration of the lens. Hence, better in Px with dry eye.

Question 19

Silicone lenses are sifter then hydrogels, why?

Answer 19

Lower water content in comparison.

Question 20

Silicone vs hydrogel lenses, which lens has a lower deposition rate?

Answer 20

Standard hydrogels

Question 21

Silicone vs hydrogel lenses, which lens has greater oxygen permeability?

Answer 21

Silicone hydrogels

Question 22

Silicone vs hydrogel lenses, which lens is more expensive?

Answer 22

Hydrogels

Question 23

Silicone vs hydrogel lenses, which lens is suitable for EW?

Answer 23

Silicone hydrogels

Question 24

Silicone vs hydrogel lenses, which lens has a risk of hypoxia?

Answer 24

Standard hydrogels

Question 25

What question is asked to guide on the type of lens that will be suitable for Px?

Answer 25

How often do you want to wear them?

Question 26

What lens is recommended for Px that want to wear lenses 2-3 times a week?

Answer 26

Dailies. RGP not suitable.

Question 27

What lens is recommended for Px that want to wear lenses 3-7 times a week?

Answer 27

Fortnightly or monthly disposable soft CL. Or RGP

Question 28

How does someone's work relate to the type of lenses selected for a Px?

Answer 28

High computer use throughout the day: silicone lens are picked over standard hydrogels since they prevent dehydration.

Question 29

What does HVID stand for?

Answer 29

Horizontal Visible Iris Diameter

Question 30

How is HVID measured?

Answer 30

Horizontal measurement from limbus to limbus. It gives the idea of total diameter of a lens.

Question 31

By what diameter should soft lenses and RGP lenses be in relation to HVID?

Answer 31

Soft lenses: need to be 2mm bigger then HVID. RGP lenses need to be small by 2mm then HVID.

Question 32

What is the full form of VPA?

Answer 32

Visible Palpebral Aperture

Question 33

How is VPA measured? And why is it important?

Answer 33

When head in neutral position- it is the lid to lid vertical measurement. It indicates how much space there is between the top and bottom lid. Gives an idea of the challenges during insertion and removal.

Question 34

VPA is more informative in soft lenses fitting or RGP?

Answer 34

RGP

Question 35

Pupil diameter is measured in which 3 conditions?

Answer 35

1. Minimum light conditions 2. Average (normal) light conditions 3. Maximum light conditions (UV light source used)

Question 36

Why is pupil size measurement relevant epically for hard CL fitting?

Answer 36

Because the optical portion that the patient is looking through needs to be bigger then their maximum pupil size.

Question 37

How are CL recorded in the record card?

Answer 37

Manufacturer name and lens name BC / TD/ Power