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OD3 (S1&2) > CLM - Irregular Cornea Fitting II - Week 7 > Flashcards

CLM - Irregular Cornea Fitting II - Week 7 Flashcards

1
Q

What are three indications for contact lenses after a corneal graft?

A

Ametropia
Irregular astigmatism
Refractive anisometropia
-difference of >4.00D

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2
Q

What percentage of grafts with >5.00D astigmatism had irregular astigmatism?

A

22%

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3
Q

What spectacle and surgical refractive procedure can correct irregular astigmatism?

A

No spectacle correction or surgical refractive procedure can correct irregular astigmatism apart from regrafting

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4
Q

List three possible causes of irregular astigmatism. What do all three result in and where?

A

Excessive and variable suture tension
Poor suture alignment
Significant asymmetric host thinning
-all three result in irregular healing at the graft margin

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5
Q

What suture technique generates the most astigmatism and why? Name an advantage of this technique over others.

A

Single interrupted sutures
-uneven distribution of tension
-surgeons have more control of astigmatism by removing individual sutures

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6
Q

What are five components to assessing a corneal graft for contact lenses?

A

History
Topography
Slit lamp examination
Slit lamp photography
Pachymetry

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7
Q

List three general graft shapes and describe them.

A

Prolate - steeper centrally, flatter peripherally
Oblate - flatter centrally, steeper peripherally
Mixed

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8
Q

Describe the C, C, and E mneumonic for RGP lenses.

A

C - centre - base curve - central fluorescein pattern
C - centration
E - clearance

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9
Q

What is a good base curve to begin with when trialling RGPs?

A

2/3rds towards the flattest K reading
i.e. 8.1/7.2 - try 7.8

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10
Q

What is a good diameter to begin with when trialling RGPs?

A

11.2mm

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11
Q

What is considered a small RGP for a corneal graft?

A

One that fits within or on the graft

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12
Q

List three potential problems that can occur with small RGPs (for corneal grafts). Explain why for each.

A

Stability - may easily be displaced off the graft
Small optic - may have flare difficulties especially at night
Small diameter - if the lens is displaced, the edge may be visible again, especially at night

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13
Q

What is considered a medium RGP for a corneal graft?

A

One that fits over the graft

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14
Q

What does the larger diameter of a medium RGP lens allow for vs a smaller one and what does this improve?

A

Allows for lid attachment with better stability

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15
Q

What may need adjustment with medium RGPs for corneal grafts and why?

A

May need to adjust peripheral curves to control edge clearance

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16
Q

What does the larger optic of a medium diameter RGP reduce vs smaller RGPs (2)?

A

Larger optic reduces flare, less interaction with the pupil, especially at night

17
Q

Is the back surface toric of a medium RGP lens for a corneal graft generally considered? Explain. What is the host astigmatism generally like vs the corneal graft?

A

Generally not, unless the graft astigmatism is ?5.00D
-generally the host cornea has much less or no significant astigmatism

18
Q

What is considered a large RGP for a corneal graft?

A

Corneo-scleral

19
Q

What does the larger design of large diameter RGPs for corneal grafts allow for the elimination of and how?

A

Eliminates superior edge interaction via significant lid attachment

20
Q

What should be aimed for regarding bearing and edge clearance with large RGP lenses for corneal grafts?

A

Moderate area of central bearing and edge clearance that allows adequate tear exchange

21
Q

What can excessive edge lift in large diameter RGPs cause?

A

May cause the lens to displace on excursions

22
Q

What is a disadvantage of sclerals and minisclerals?

A

Expensive and time consuming

23
Q

List some advantages of scerals and minisclerals.

A

Comfortable
Good vision
Hard to lose
Hard to break

24
Q

What should you look for at the edge of the lens with sclerals and minisclerals?

A

Compression of conjunctival blood vessels
-edge lift if so

25
Q

List the three most common causes of penetrating graft failures, in order.

A

Rejection
Endothelial cell failure
Infection

26
Q

Does graft failure increase with increasing numbers of graft surgeries performed on the same eye, or is this negligible?

A

It increases

27
Q

When is the incidence of graft rejection highest?

A

First year following transplantation

28
Q

Can graft rejection be controlled?

A

With early intervention, yes
-pred forte

29
Q

What acronym is important for patients with a corneal graft?

A

RSVP
Redness
Sensitivity to light
Vision changes
Pain/soreness

30
Q

What are 5 signs of graft rejection that can be seen using a slit lamp?

A

Limbal/bulbar hyperaemia
Dilated blood vessels towards the graft
Graft oedema
Anterior chambel reaction
Fluorescein staining

31
Q

How does epithelial infiltration occur in graft rejection?

A

As discrete sub-epithelial infiltrates

32
Q

When does epithelial rejection typically occur after graft surgery?

A

Within the first year

33
Q

Is stromal rejection common or uncommon?

A

Uncommon

34
Q

What is the most common form of graft rejection (which layer)? What is seen with this (3)?

A

Endothelium
-keratic precipitates scattered across the endothelium
-folds in descemet’s membrane
-stromal oedema

35
Q

What is khodadoust line? What does the graft look like ahead and behind this line?

A

Keratic precipitates in line advancing in from the peripheral cornea
-graft clear ahead of the line, and oedematous behind it

36
Q

What should be measured when corneal graft rejection is detected?

A

IOP

37
Q

Does elevated IOP increase or decrease the viability of the endothelium?

A

Decrease

38
Q

What may ocassionally be required for endothelial rejection in a corneal graft?

A

Maintenance low dose steroids for months or years

OD3 (S1&2) (114 decks)

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