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

CLM - Irregular Cornea Fitting I - Week 7 Flashcards

1
Q

What is a keratoplasty?

A

Corneal transplant/graft

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2
Q

What is the oldest form of human transplantation?

A

Blood transfusion, followed by keratoplasty

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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

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4
Q

What age are most donor eyes?

A

> 60

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5
Q

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

A

Yes, significantly

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6
Q

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

A

Severe infections
Haematological malignancies
HIV
Hepatitis

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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

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8
Q

What is the waiting time for a corneal graft?

A

6-9 months

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9
Q

How soon is the cornea removed from a donor eye?

A

Within hours of death

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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

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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

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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

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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

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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

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15
Q

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

A

Yes

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16
Q

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

A

Increases structural integrity

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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

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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

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19
Q

What is the graft size determined by (2)?

A

Size of the recipient cornea
Area of the disease

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20
Q

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

A

Increases

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21
Q

How wide are full thickness corneal grafts in diameter typically?

A

7.5-8.5mm

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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

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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

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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

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25
Q

How is the graft centred (2)?

A

It is centred over the pupil and displaced slightly nasally

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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

OD3 (S1&2) (114 decks)

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