CLM - Specialty Contact Lens Fitting - Week 10

Question 1

What percentage of keratoconic patients fail to adapt to RGP lenses?

Answer 1

10%

Question 2

List three disadvantages of RGPs for keratoconus.

Answer 2

Initial adaptation and comfort
Lens ejection/stability
Unilateral fitting

Question 3

List three types of specialty contact lenses.

Answer 3

Corneoscleral lenses
Hybrid lenses
Miniscleral lenses

Question 4

What is the physically larger diameter RGP lenses of corneo-scleral designs to optimise? What is the comofrt like compared with corneal RGPs?

Answer 4

Optimises centration
Better comfort profile

Question 5

How do corneo-scleral RGPs interact with the limbus?

Answer 5

They vault the limbus

Question 6

How does tear exchange occur with corneo-scleral lens designs?

Answer 6

Pumping action

Question 7

What are E series ACL limbal lift designs for (4)?

Answer 7

Normal eyes
Non-proud grafts
PMD
High ametropia

Question 8

What are K series ACL limbal lift designs for?

Answer 8

Keratoconus

Question 9

What are G series ACL limbal lift designs for?

Answer 9

Advanced/highly proud corneal grafts

Question 10

Compare the cost of E series lenses to regular RGPs.

Answer 10

Marginally more expensive

Question 11

Are E series lenses more prone to lens ejection? What about debris entrapment?

Answer 11

Very good resistance to both

Question 12

Can E series lenses be fit unilaterally?

Answer 12

Yes

Question 13

Can E series lenses be combined with SCLs or are they incompatible?

Answer 13

Can be combined

Question 14

How do hybrid lenses deal with the main corneal irregularities of corneal ectasia?

Answer 14

Vault them

Question 15

Are the fitting concepts of hybrid lenses the same as SCLs and RGPs?

Answer 15

No

Question 16

What are hybrid lense ideal for?

Answer 16

Oval/central/dectentred cones

Question 17

What three indications may hybrid lenses be suitable for?

Answer 17

Globus/pellucid degeneration
Other corneal irregularities (LASIK induced ectasia or trauma)
Post-INTACs, post-CXL

Question 18

Are hybrid lenses also suitable for corneal grafts?

Answer 18

No

Question 19

What are hybrid lenses a priority choice for (5)?

Answer 19

Monocular corrections
Strong history of RGP intolerance
Part-time wear
Dusty/windy occupational environment
Application for sport/recreational activity

Question 20

What is the aim when vaulting the cornea using hybrid lenses?

Answer 20

Aim for the least amount of vault that allows complete apical clearance

Question 21

Describe how hybrid lenses are applied to the eye.

Answer 21

Bowl is completely filled with non-preserved saline (and a drop of NaFl when assessing patient’s fitting thechnique)
Patient leans forward with their head parallel to the floor and eye wide open
Lens is gently applied directly to the eye

Question 22

How do you assess hybrid lens application technique? What do air bubbles indicate?

Answer 22

Check for air bubbles beneath the lens
Cannot be removed by lens manipulation
Requires removal and re-application

Question 23

During hybrid lens removal, is the use of lubricating drops recommended?

Answer 23

No

Question 24

What can be worn to optimise grip on the lens when removing hybrid lenses?

Answer 24

Latex gloves

Question 25

What is the outer landing zone with hybrid lenses? What about inner landing zone?

Answer 25

Outer - Region of the soft contact lens in contact with the cornea Inner - outer region of the RGP in contact with the cornea

Question 26

How do the outer and inner landing zones appear with fluorescein?

Answer 26

Outer - a relatively thick dark band Inner - relatively thinner dark band

Question 27

Is a feather touch ideal with hybrid lenses or do you want complete clearance? What should be barely visible?

Answer 27

Complete clearance, though with as little vault as necessary Pupil should barely be visible

Question 28

What is the most common source of failure when fitting hybrid lenses?

Answer 28

Over-vault

Question 29

What is next after determining vault depth? What should you start with?

Answer 29

Determining skirt curvature -start with medium skirt

Question 30

What should you aim for when determining skirt curvature in terms of fluorescein staining (hybrid lenses, 2)?

Answer 30

Fluorescein thinning in the ILZ Gentle bearing in the OLZ

Question 31

What is lens movement like in hybrid lenses?

Answer 31

Similar to soft contact lenses

Question 32

How do skirts that are too flat or steep stain (hybrid lenses)?

Answer 32

Too flat - OLZ too dark Too steep - OLZ too bright -in both cases the ILZ is barely noticed, not ideal, it should be a thin faint line

Question 33

When the ideal fluorescein pattern is achieved, what should you do (hybrid lenses)?

Answer 33

Over-refraction

Question 34

How is the vault depth determined with topography-based fitting?

Answer 34

Measure the mean saggital height (um) then use a guide and select a depth corresponding to your mean value and trial it Adjust accordingly based on fluorescein staining

Question 35

How is the skirt curvature determined with topography-based fitting? What power map is used?

Answer 35

Measure vertical displacement (mm) of the corneal apex from the centre of the reflected mires using tangential power laps Select based on a guide, then adjust accordingly

Question 36

Do minisclerals have movement?

Answer 36

No, essentially none

Question 37

Are minisclerals a sealed system or does it permit tear exchange?

Answer 37

Sealed system

Question 38

Are minisclerals considered small or large diameter?

Answer 38

Large

Question 39

Do minisclerals have a small or large optic zone? What does this mean for edge awareness?

Answer 39

Large optic zone -minimal edge awareness

Question 40

Is vision with minisclerals good at night?

Answer 40

Excellent

Question 41

What are three applications of minisclerals?

Answer 41

All forms of corneal irregularities RGP intolerance Dry eye disease or exposure keratopathy

Question 42

What is the process of miniscleral application?

Answer 42

The same as hybrid lenses

Question 43

Can gas bubbles be displaced in minisclerals?

Answer 43

No

Question 44

Describe the process of removing minisclerals.

Answer 44

Manipulate the lower lid against the edge of the lens to encourage tear exchange, breaking the seal Gently attach the DMV applicator to the edge of the lens and tilt the lens off the eye Do not suction the applicator to the middle and try pulling it off

Question 45

What should you quantify when assessing miniscleral fit?

Answer 45

Tear thickness profile across the lens

Question 46

What two things should you watch out for with minisclerals?

Answer 46

Corneal staining Conjunctival blanching