CLM - Irregular Cornea Fitting I - Week 7 Flashcards
What is a keratoplasty?
Corneal transplant/graft
What is the oldest form of human transplantation?
Blood transfusion, followed by keratoplasty
Is everyone a universal donor for keratoplasty? Is blood typing required? Does donor age have an impact?
Yes
No blood typing required
Donor age not as important as other tissue transplants
What age are most donor eyes?
> 60
Do grafts from donors <50 have better survival raves vs >60?
Yes, significantly
What diseases need to be excluded from corneal donors (4)?
Severe infections
Haematological malignancies
HIV
Hepatitis
What is the longevity of a corneal graft? Explain.
Up to 150 years, exact number unknown
If most grafts come from donors aged 60+, most grafts will be very old
What is the waiting time for a corneal graft?
6-9 months
How soon is the cornea removed from a donor eye?
Within hours of death
What is a penetrating keratoplasty? List all the layers of the cornea involved (5).
Full thickness graft
- epithelium
- bowman’s layer
- stroma
- descemet’s membrane
- endothelium
What is a deep anterior lamellar keratoplasty? List all the layers of the cornea involved (3).
A partial thickness graft
- epithelium
- bowman’s membrane
- stroma
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 partial thickness graft -stroma -descemet's membrane -endothelium Tissue is prepared using an automated microkeratome
What is a descemet’s membrane endothelial keratoplasty? List all the layers of the cornea (2).
Partial thickness graft
- descemet’s membrane
- endothelium
Compare the rates of full thickness, DALK, DSAEK, and DMEK procedures over recent times.
Full thickness rates are decreasing, while the others are increasing, notably DSAEK and DMEK
Do all partial thiccness keratoplasties preserve descemet’s membrane and endothelium?
Yes
How does retaining descemet’s membrane affect the post-graft cornea?
Increases structural integrity
Where do most corneal graft rejections occur? Retaining what layer will minimise the risk of rejection?
Uusally begins in the endothelium
Retaining the endothelium reduces the chance of rejection
What anaesthesia is used for corneal graft procedures (technique not drug)?
General or retrobulbar with IV sedation
Majority done under local anaesthesia
What is the graft size determined by (2)?
Size of the recipient cornea
Area of the disease
Does the risk of rejection increase or decrease with increasing graft size?
Increases
How wide are full thickness corneal grafts in diameter typically?
7.5-8.5mm
What instrument is used to excise the host cornea and what does it look like? What is used to maintain stability?
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
What risks are presented if the graft size is >8.5mm, aside from increased rejection risk (3)?
Post-op increase in IOP
Anterior synaechiae
Vascularisation
What risk is presented if the graft size is >7.0mm?
Smaller sizes give rise to higher astigmatism due to increased tension from the host
How is the graft centred (2)?
It is centred over the pupil and displaced slightly nasally