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OD3 (S1&2) > CLM - Specialty Contact Lens Fitting - Week 10 > Flashcards

CLM - Specialty Contact Lens Fitting - Week 10 Flashcards

1
Q

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

A

10%

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2
Q

List three disadvantages of RGPs for keratoconus.

A

Initial adaptation and comfort
Lens ejection/stability
Unilateral fitting

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3
Q

List three types of specialty contact lenses.

A

Corneoscleral lenses
Hybrid lenses
Miniscleral lenses

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4
Q

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

A

Optimises centration
Better comfort profile

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5
Q

How do corneo-scleral RGPs interact with the limbus?

A

They vault the limbus

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6
Q

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

A

Pumping action

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7
Q

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

A

Normal eyes
Non-proud grafts
PMD
High ametropia

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8
Q

What are K series ACL limbal lift designs for?

A

Keratoconus

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9
Q

What are G series ACL limbal lift designs for?

A

Advanced/highly proud corneal grafts

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10
Q

Compare the cost of E series lenses to regular RGPs.

A

Marginally more expensive

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11
Q

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

A

Very good resistance to both

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12
Q

Can E series lenses be fit unilaterally?

A

Yes

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13
Q

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

A

Can be combined

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14
Q

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

A

Vault them

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15
Q

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

A

No

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16
Q

What are hybrid lense ideal for?

A

Oval/central/dectentred cones

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17
Q

What three indications may hybrid lenses be suitable for?

A

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

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18
Q

Are hybrid lenses also suitable for corneal grafts?

A

No

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19
Q

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

A

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

20
Q

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

A

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

21
Q

Describe how hybrid lenses are applied to the eye.

A

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

22
Q

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

A

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

23
Q

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

A

No

24
Q

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

A

Latex gloves

25
Q

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

A

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

26
Q

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

A

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

27
Q

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

A

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

28
Q

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

A

Over-vault

29
Q

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

A

Determining skirt curvature
-start with medium skirt

30
Q

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

A

Fluorescein thinning in the ILZ
Gentle bearing in the OLZ

31
Q

What is lens movement like in hybrid lenses?

A

Similar to soft contact lenses

32
Q

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

A

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

33
Q

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

A

Over-refraction

34
Q

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

A

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

35
Q

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

A

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

36
Q

Do minisclerals have movement?

A

No, essentially none

37
Q

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

A

Sealed system

38
Q

Are minisclerals considered small or large diameter?

A

Large

39
Q

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

A

Large optic zone
-minimal edge awareness

40
Q

Is vision with minisclerals good at night?

A

Excellent

41
Q

What are three applications of minisclerals?

A

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

42
Q

What is the process of miniscleral application?

A

The same as hybrid lenses

43
Q

Can gas bubbles be displaced in minisclerals?

A

No

44
Q

Describe the process of removing minisclerals.

A

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

45
Q

What should you quantify when assessing miniscleral fit?

A

Tear thickness profile across the lens

46
Q

What two things should you watch out for with minisclerals?

A

Corneal staining
Conjunctival blanching

OD3 (S1&2) (114 decks)

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