Topic 13 Corneal Grafts

Overall yield:

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Clinical exam:

Viva:

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Essay:

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MCQ:

<S> Opening question No. 1 : Tell me about corneal grafts

"Corneal graft is a surgical procedure in which diseased host cornea is replaced by healthy donor cornea."

"Broadly, corneal grafts can be either partial thickness/lamellar or full thickness/ penetrating."

"The indications for full thickness corneal graft are ..." "Prior to the operation, the patient must be evaluated for..."

CO Exam tips:

• This is a gift question! You should be able to talk for at least a few minutes ■■i? without any interruption

Opening question No. 2: What are the indications for penetrating keratoplasty (PKP)?

"The indications for corneal grafts can be ..."

Indications for PKP

1. Optical

• Bullous keratopathy (pseudophakic and aphakic)

• Keratoconus

• Corneal dystrophy

• Corneal inflammatory diseases — interstitial keratitis, HSV

• Corneal traumatic scars

• Failed grafts

2. Tectonic

• Corneal perforation

• Peripheral corneal thinning

3. Therapeutic

• Infective keratitis

What are preoperative factors to look out for prior to PKP?

Preoperative factors

1. Evaluate patient's ocular condition and manage poor prognostic factors prior to PKP

• Factors (Big 4 poor prognostic factors)

• Ocular inflammation

• Corneal vascularization

• Ocular surface abnormalities

• Associated lid abnormality (entropian, ectropian)

• Tear film dysfunction and dry eyes

CO Exam tips:

• Remember the BIG 4 poor prognostic factors well

• Other factors to consider

• Corneal hyposthesia

• Cornea irregularity

• Pre-existing cataract (consider triple procedure)

• Structural changes of AC (peripheral anterior synechiae, rubeosis) Assess visual potential

• Retinal and macular conditions (e.g. cystoid macular edema)

• Optic atrophy

Topical antiblotics/steroids/cyclosporin A if necessary

Opening question No. 3: How do you perform a PKP? Steps in PKP

1. Preoperative preparation

• Maumanee speculum

• Superior and inferior rectus bridle suture with 4/0 silk

• Flieringa ring if necessary (indications: post vitrectomy, aphakia, trauma, children)

• Overlay suture if necessary (7/0 silk at limbus)

• Check recipient bed size with Week trephine (usually 7.5mm)

2. Donor button

• Check corneoscleral disc

• Harvest donor cornea button with Week trephine on Troutman punch

• Approach from posterior endothelial side

• Use trephine size 0.25-0.5mm larger than recipient bed

• Keep button moist with viscoelastic

3. Recipient bed

• 3-point fixation (2 from bridle suture, one with forceps)

• Week trephine imprint to check size and centration

• Other types of trephine

• Baron Hessberg trephine and Hannah trephine (suction mechanism)

• Set trephine to 0.4mm depth

• Enter into AC with blade

• Complete incision with corneal scissors

4. Fixation of graft

• Fill AC with viscoelastic

• Place donor button on recipient bed

• 4 cardinal sutures with 10/0 nylon (at 12 o'clock first, followed by 6, 3 and then 9)

• 16 interrupted sutures

• Advantages of interrupted sutures

• Easier for beginners

• Better for inflamed eyes and eyes with vascularization

NOTES

• "How do you check the corneoscleral disc?"

• Media (clarity and colour)

• Corneal button (clarity, thickness, irregularity, surface damage)

NOTES

• "Why is the donor button made larger than recipient bed?"

• Because donor button is punched from posterior endothelial surface

• Tighter wound seal for graft

• Increases convexity of button (less peripheral anterior synechiae postop)

• More endothelial cells with larger button

• Other suture techniques

• Continuous suture

• Better astigmatism control

• Combined continuous and interrupted sutures

5. End of operation

• Check water tightness and astigmatism with keratometer

• Subconjunctival steroids/antibiotics

How is the donor corneal button stored?

"Storage media can be divided into ..."

Storage media

1. Short term (days)

• Moist chamber

• Storage duration: 48 hours

• McCarey-Kaufman medium

• Standard tissue culture medium (TC199, 5% dextran, antibiotics)

• Storage duration: 2-4 days

2. Intermediate term (weeks)

• Dexsol/Optisol/Ksol/Procell

• Standard tissue culture medium (TC199) plus chondroitin sulphate, HC03 buffer, amino acid, gentamicin

• Organ culture

• Advantage: Decrease rejection rate? (culture kills off antigen-presenting cells)

• Disadvantage: Increase infection rate?

• Storage duration: 4 weeks

3. Long term (months)

• Cryopreservation

• Liquid nitrogen

• Storage duration: 1 year

• Disadvantages: Expensive and unpredictable results

"The contraindications included patients with ..."

Contraindications for cornea donation 1. Systemic diseases

• Death from unknown cause

• CNS diseases of unknown cause

• Creutzfeld-Jacob disease, CMV encephalitis, slow virus diseases

• Infections

• Congenital rubella, rabies, hepatitis, AIDS

• Septicemia

• Malignancies

• Leukemias, lymphomas, disseminated cancer

What are the contraindications for donation of corneas?

2. Ocular diseases

• Intraocular surgery

• History of glaucoma and iritis

• Intraocular tumors

• Corneas are difficult to handle

• Small diameter and friable

• Very steep cornea (average keratometry = 50D)

• Low endothelial cell count

4. Duration of death > 6 hours

<3> WhSitare the complications of corneal grafts?

'The complications can be divided into complications specific to corneal grafts or general complications of intraocular surgery." "They can occur in the early or late postoperative period ..."

Complication of corneal grafts

1. Early postoperative

• Glaucoma or hypotony

• Persistent epithelial defect

• Endophthalmitis

• Recurrence of primary disease

2. Late postoperative

• Infective keratitis

• Recurrence of disease

• Astigmatism

• Persistent iritis

• Late endothelial failure

3. Others complications of intraocular surgery

• Expulsive hemorrhage

• Retrocorneal membrane

<3> What are causes of graft failure?

"Graft failure can be divided into early failure or late failure." Graft failure

• Primary donor cornea failure

• Unrecognized ocular disease

• Low endothelial cell count

• Storage problems

• Surgical and postoperative trauma

• Trephination

• Intraoperative damage

• Recurrence of disease process (e.g. infective keratitis)

CO Exam tips:

• Do not confuse graft failure with graft rejection (which is one of the causes of graft failure and: may or may not lead to failure)

• Infective keratitis 2. Late failure (> 72 hours)

• Rejection (30% of late graft failures)

• Persistent epithelial defect

• Infective keratitis

• Recurrence of disease process

• Late endothelial failure

<S> What are factors which affect graft survival?

"The factor which affect graft survival can be divided Into ..."

Graft survival

1. Factors associated with higher risk of graft rejection

• Repeat grafts

• Position of graft (eccentric graft)

• Presence of peripheral anterior synechiae

• Exposed sutures

• Deep stromal vascularization

2. Other factors associated with graft failure

• Preexisting glaucoma and high IOP

• Intraocular inflammation (iritis)

CO Exam tips:

• Remember the BIG 4 poor prognostic factors!

<§> Howdo you grade corneal graft prognosis according to disease categories?_

Brightbill's classification

GRADE I (Excellent)

• Keratoconus

• Lattice and granular dystrophy

• Traumatic leukoma

• Superficial stromal scars GRADE II (Good)

• Bullous keratopathy

• Fuch's dystrophy

• Macular dystrophy

• Small vascularized scars

• Interstitial keratitis

. Failed Grade I PKP

• Combined PKP and cataract op GRADE III (Fair)

• Active bacterial keratitis

• Vascularized cornea

• Active HSV keratitits

• Congenital hereditary endothelial dystrophy . Failed Grade II PKP

GRADE IV (Guarded)

• Active fungal keratitis

• Congenital glaucoma

El Exam tips:

• Just remember the ones in BOLD!

Pediatric grafts

Mild keratoconjunctivitis sicca Mild chemical burns Corneal blood staining Corneal staphylomas Failed Grade III PKP GRADE V (Poor)

• Severe keratoconjunctivitis sicca

(Stevens Johnson's syndrome, ocular cicatrical pemphigoid, chemical and thermal burns)

Tell me about graft rejection

"Graft rejection is a type 4 immune reaction."

"It can be divided into epithelial, subepithelial, stromal and endothelial rejection."

Graft rejection

1. Pathophysiological basis of rejection

• Type 4 immunological reaction

• Divided into: epithelial, subepithelial, stromal and endothelial rejection

• Immunological phenomenon

2. Bisk factors

• Repeat grafts

• Position of graft (eccentric graft)

• Peripheral anterior synechlae

• Exposed sutures

• Deep stromal vascularization

3. Clinical features

• 2 weeks onwards (if less than 2 weeks, consider other diagnosis)

• Epithelial rejection

• Epithelial rejection line (advancing lymphocytes, replaced by epithelial cells from recipient)

• Usually low grade, asymptomatic, eye is quiet

• Subepithelial rejection

• Nummular white infiltrates (Krachmer's spots)

• Mild AC activity

• Stromal rejection

• Most important of the 4 types

NOTES

"What is the evidence that rejection is an immune phenomenon?"

• Rejection of 2nd graft from same donor begins after shorter interval and progresses more rapidly

• Brief period of latency (2 weeks) before rejection

• Rejection correlates with amount of antigen introduced in graft

• Neonatally thymectomized animals reject grafts with difficulty

NOTES

"What are the problems of large grafts?"

• Increased risk of rejection (nearer vessels)

• Increase IOP (more peripheral anterior synechiae)

• Large epithelial defect (limbal stem cell failure)

Redness Pain

Signs

• Limbal injection

• Keratic precipitates

• Endothelial rejection line (Khodadoust's line)

• Stromal edema Endothelial rejection

• Combination of stromal and endothelial rejection

^Js Clinical approach to corneal grafts

This patient has a corneal graft... The graft has interrupted sutures...

Look for

• Pseudophakic/aphakic (pseudophakic or aphakic bullous keratopathy?)

• Hazy graft/local edema

• Keratic precipitates, AC cells, Khodadoust's line

• Peripheral anterior synechiae

• Stromal vascularization

• Other eye for corneal dystrophies, keratoconus

I'll like to

What is the role of cyclosporin A in corneal grafts?

1. Indications (high risk of graft rejection)

• Young patient

• Repeat grafts

• Large grafts/sclerokeratoplasty

• Deep stromal vascularisation

■ Limbal allografts (chemical injury, SJS)

• Post graft rejection

2. Investigations prior to treatment

t Renal function tests and uric acid levels

• Fasting blood glucose and HB A1C

• Liver function tests

• Hepatitis B screen and serology for hepatitis C, herpes zoster, CMV and HIV

3. Treatment regime

• Cyclosporine A (neoral) 5mg/kg/day in 2 divided doses

• Treatment continued for at least 1 year

• Dosage gradually tapered after 3 months

4. Monitoring during treatment

• CBC, renal function, liver function . CXR, ECG

• Serum cyclosporine level

• Co-management with renal transplant physician

<£> Tell me about lamellar keratoplasty

"Lamellar keratoplasty is a partial thickness corneal graft."

Lamellar keratoplasty

1. Indications

• Partial thickness corneal diseases

• Superficial corneal dystrophies (Reis Buckler)

• Superficial corneal scars

• Recurrent pterygium

• Corneal thinning (Terrien's marginal degeneration)

• Corneal perforation

• Congenital lesions (limbal dermoid)

• Superficial tumors

2. Advantages

« Minimal donor tissue requirements

• No intraocular entry

• Faster wound healing and rehabilitation

• Lower risk of rejection and therefore less use of topical steroids

3. Disadvantages

• Does not replace damaged endothelium

• Interface scarring

• Technically more difficult

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