CLM - Irregular Cornea Fitting I - Week 7 Flashcards

1
Q

What is a keratoplasty?

A

Corneal transplant/graft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the oldest form of human transplantation?

A

Blood transfusion, followed by keratoplasty

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Is everyone a universal donor for keratoplasty? Is blood typing required? Does donor age have an impact?

A

Yes
No blood typing required
Donor age not as important as other tissue transplants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What age are most donor eyes?

A

> 60

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Do grafts from donors <50 have better survival raves vs >60?

A

Yes, significantly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What diseases need to be excluded from corneal donors (4)?

A

Severe infections
Haematological malignancies
HIV
Hepatitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the longevity of a corneal graft? Explain.

A

Up to 150 years, exact number unknown

If most grafts come from donors aged 60+, most grafts will be very old

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the waiting time for a corneal graft?

A

6-9 months

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How soon is the cornea removed from a donor eye?

A

Within hours of death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a penetrating keratoplasty? List all the layers of the cornea involved (5).

A

Full thickness graft

  • epithelium
  • bowman’s layer
  • stroma
  • descemet’s membrane
  • endothelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a deep anterior lamellar keratoplasty? List all the layers of the cornea involved (3).

A

A partial thickness graft

  • epithelium
  • bowman’s membrane
  • stroma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a descemet’s stripping automated endothelial keratoplasty? List all the layers of the cornea involved (3). Describe how the graft tissue is prepared.

A
A partial thickness graft
-stroma
-descemet's membrane
-endothelium
Tissue is prepared using an automated microkeratome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a descemet’s membrane endothelial keratoplasty? List all the layers of the cornea (2).

A

Partial thickness graft

  • descemet’s membrane
  • endothelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Compare the rates of full thickness, DALK, DSAEK, and DMEK procedures over recent times.

A

Full thickness rates are decreasing, while the others are increasing, notably DSAEK and DMEK

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Do all partial thiccness keratoplasties preserve descemet’s membrane and endothelium?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does retaining descemet’s membrane affect the post-graft cornea?

A

Increases structural integrity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where do most corneal graft rejections occur? Retaining what layer will minimise the risk of rejection?

A

Uusally begins in the endothelium

Retaining the endothelium reduces the chance of rejection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What anaesthesia is used for corneal graft procedures (technique not drug)?

A

General or retrobulbar with IV sedation

Majority done under local anaesthesia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the graft size determined by (2)?

A

Size of the recipient cornea

Area of the disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Does the risk of rejection increase or decrease with increasing graft size?

A

Increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How wide are full thickness corneal grafts in diameter typically?

A

7.5-8.5mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What instrument is used to excise the host cornea and what does it look like? What is used to maintain stability?

A

A trephine - an instrument with a circular blade that suctions onto the cornea
When twisted, the blade slices the cornea
The rest is incised manually
Vacuum is used to maintain suction and stability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What risks are presented if the graft size is >8.5mm, aside from increased rejection risk (3)?

A

Post-op increase in IOP
Anterior synaechiae
Vascularisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What risk is presented if the graft size is >7.0mm?

A

Smaller sizes give rise to higher astigmatism due to increased tension from the host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How is the graft centred (2)?

A

It is centred over the pupil and displaced slightly nasally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

For the host cornea, briefly describe how layers are separated in deep anterior lamellar keratoplasty (3).

A

Trephine used to incise cornea 2/3rds
Air bubble injected
Viscoelastic injected between descemet’s membrane and the stroma

27
Q

For the donor graft, briefly describe how layers are separated in deep anterior lamellar keratoplasty (2).

A

Descemet’s membrane is stained with tryptophan blue

It is then manually removed

28
Q

Compare visual outcomes in deep anterior lamellar keratoplasty vs penetrating keratoplasty. Explain why they are so.

A

Penetrating keratoplasty can often achieve 6/6= vision

Due to the extra interface, final best VA for DALK is often reduced a line

29
Q

Is deep anterior lamellar keratoplasty easier or more challenging to carry out?

A

More challenging

30
Q

What are the three most common diseases treated by penetrating keratoplasty (in order)?

A

Keratoconus
Failed previous graft
Bullous keratopathy

31
Q

What are the two most common diseases treated by partial thickness keratoplasties?

A

Fuch’s endothelial corneal dystrophy

Bullous keratopathy

32
Q

Corneal grafts performed for which disease has significantly better graft survival vs other indications?

A

Keratoconus

33
Q

Post graft surgery, how long does it take for complete corneal epithelial healing? what is this important for?

A

94% in 7 days

-important to re-establish barrier to infection

34
Q

What is the normal endothelial count in a 20 year old vs 80? what may happen if the count reaches 500-1000?

A

2,800 cells/mm2 - 20 year old
2,500 to 2,000 cells/mm2 - 80 year old
Corneal decompensation may occur at low counts

35
Q

Are endothelial cells lost at the graft-host junction after graft surgery? What is the rate of endothelial cell loss like after surgery?

A

Cells lost at the junction

Ongoing endothelial cell loss still occurs

36
Q

Is endothelial cell loss more rapid in the graft or the host cornea following graft surgery?

A

More rapid in the graft

37
Q

Following graft surgery, when does majority of endothelial cell loss occur?

A

Within the first two years

38
Q

How does endothelial cell loss compare in penetrating keratoplasty vs DALK?

A

Significantly less endothelial loss due to retention of host endothelium

39
Q

Where is corneal sensitivity maximal?

A

At the corneal apex

40
Q

What happens to corneal nerves in penetrating keratoplasty and DALK? What is corneal sensitivity like post surgery?

A

They are severed

Central grafts are completely or markedly hypo-aesthetic

41
Q

Compare corneal sensitivity after a penetrating keratoplasty vs DALK.

A

More sensitivity in DALK vs PK

42
Q

List four complications following graft surgery.

A

Flat anterior chamber
Acute post-operative glaucoma
Persistent epithelial defects
Infection

43
Q

Describe a fixed dilated pupil following graft surgery and how it can occur (2).

A

Due to ischameic atrophy of the iris sphincter secondary to an iris strangulation

44
Q

List three ways glaucoma can occur after graft surgery.

A
Chronic secondary (anterior synaechiae)
Steroid induced
Secondary inflammatory (uveitis)
45
Q

Can cataracts occur after graft surgery?

A

Yes, posterior subcapsular from steroid

46
Q

List three optical complications after graft surgery.

A

High degree of regular astigmatism
Irregular astigmatism
Significant anisometropia

47
Q

What is vision like immediately after graft surgery and why? What happens over the next few weeks?

A

Hazy due to folds in descemet’s membrane

Gradually improves over weeks and months as graft endothelium clears graft stromal oedema

48
Q

Is it possible to predict the quality of vision following graft surgery?

A

Not

49
Q

What can be done to reduce excessive astigmatism (2)?

A

Monitor it using topography and selectively remove/insert sutures

50
Q

What is vision often like with sutures in and once they are removed? Explain why.

A

Patients may achieve good quality vision with sutures in as they maintain regular curvature
Once removed, stresses within the graft can influence host toricity
-vision may deteriorate

51
Q

Is vision likely to improve followjng suture removal?

A

No

52
Q

If there is significant myopia, regular and/or irregular astigmatism, will they be compensated for by the removal of the sutures?

A

No

53
Q

Compare VA outcomes in full thickness vs DALK grafts (percentages).

A

Full thickness grafts for keratoconus - 75% achieve a post graft VA of 6/12
DALK - 50% achieve a post graft VA of 6/12

54
Q

What percentage of graft recipients have regular astigmatism (and what magnitude)? Is there a difference in rates between full/partial thickness grafts?

A

Up to 50% had regular astigmatism of >5.00D

-no difference between full/partial thickness grafts

55
Q

Is topography useful for information on elevation of the peripheral host cornea?

A

No, limited information

56
Q

What are the four components of graft assessment?

A

Topography maps
Corneal toricity - regular/irregular astigmatism
Graft diameter - measure it
Location of the graft - displaced from the corneal centre

57
Q

What can cause scarring/haze after graft surgery (6)?

A
Generalised scarring
Suture scars
Overall haze due to aged graft
Peripheral haze due to arcus
Rejection episodes
Herpes scars
58
Q

What is meant by blood vessel ingrowth?

A

Blood vessel growth to the graft - a pathway for inflammation

59
Q

What should be noted when assessing active blood vessel ingrowth (5)?

A
Size
Number
Location
Extent within the host
Extent within the graft
60
Q

How does inactive blood vessel ingrowth appear and what is a technique to see them?

A

Ghost vessels - retro-illumination

61
Q

What is the most significant factor in determining graft failure?

A

Corneal vascularisation

62
Q

Consider graft surgery to treat keratoconus. Can the host cornea continue to thin (2)? Explain what can happen after (2).

A

It can continue to develop
-take particular note from 4 to 8 o’clock
If the host cornea thins too much, it can cause sagging and an inferior bulging of the graft

63
Q

Is refractive keratoplasty done while sutures are still in place or once they are removed?

A

Typically wait until all sutures are out before doing refractive keratoplasty

64
Q

What is refractive keratoplasty?

A

Insertion of sutures to reduce corneal astigmatism