EYE BANKING&

KERATOPLASTY

EYE BANKING

An eye bank is an organization which obtains,evaluates and distributes eyes from humanitarian minded citizens for use in corneal transplantation, research and education

To ensure patient safety,the donated eyes are evaluated under strict medical standards

All donated eyes not suitable for corneal transplantation are used for valuable research and education

CONTRAINDICATIONS OF EYE DONATION

EBAA has developed extensive criteria for screening donor corneas to avoid transmissable infections and other conditions.Contraindicatons include-

Death of unknown cause Unknown CNS disease or certain infections

(eg. Creutzfeldt-Jacob disease,SSPE,Progressive multifocal leukoencephalopathy,congenital rubella,rabies,Reye syndrome,active viral encephalitis,encephalitis of unknown origin)

CONTRAINDICATIONS

Active septicemia Social ,clinical or laboratory evidence

suggestive of HIV infecton,syphilis, or active viral hepatitis)

Leukemias or active disseminated lymphomas

Active bacterial or fungal endocarditis Active ocular or intraocular inflammation

such as iritis,scleritis, conjunctivitis,choroiditis

CONTRAINDICATIONS

Intrinsic malignanciessuch as malignant anterior segment tumors,adenocarcinoma in the eye of primary or metastatic origin,and retinoblastoma

Congenital or acquired eye disorders that would preclude successful surgical outcome: any central donor corneal scar or pterygium involving the central 8mm clear zone(optical area of the donor button), keratoconus, keratoglobus, or Fuch’s dystrophy

CONTRAINDICATIONS

Prior refractive coneal surgery such as radial keratotomy(RK), PRK, LASIK, and lamellar inserts,although for use in endothelial keratoplasty such as DSAEK, refractive laser surgery may not disqualify a donor.

Hepatitis B surface antigen- positive donors, hepatitis C seropositive donors.

Corneas from patients with prior intraocular surgery (cataract, IOL implants, glaucoma filtration) may be accepted if endothelial adequacy is documented by specular microscopy

Other factors to be considered includes •slit lamp appearance of donor tissue•specular microscopic data( endothelial

cell counts <2000 cells/mm2 are not used)

Death to preservation time(optimal range <12-18 hrs)

Tissue storage time prior to keratoplasty

Donor ageMost eye banks establish a lower age

limit of 24 months and an upper age limit of 70 years

Storage media

The McCarey-Kaufman tissue transport medium developed in the early 1970’s significantly reduced endothelial cell attrition, allowing corneal buttons to be safely transplanted after being stored for up to 4 days at 4◦C.

Most commonly used preservative medium is Optisol-GS(Bausch & Lomb, Irvine,CA) which includes 2.5%chondroitin sulphate, 1% dextran, ascorbic acid, vitamin B 12, and the antibiotics gentamycin and streptomycin.

Storage media

Corneal transplantation

Corneal transplantation refers to surgical replacement of a full-thickness or lamellar portion of the host cornea with that of a donor eye.

Allograft-if the donor is another person Autograft-use of donor tissue from the

same or fellow eye

Pre-operative evaluation

Complete eye examination,including a detailed social history to help determine the patient’s compliance postoperatively.

Ocular surface problems-dry eyes,trichiasis,exposure,blepharitis,and rosacea must be recognized and treated

Pre existing glaucoma or ocular inflammation should be controlled.

Active keratitis or uveitis is treated and the eye should be quiet for several months prior to surgery.

FFA and OCT can be helpful in detecting retinal problems-CME and ARMD

Poor prognostic factors-deep corneal vascularization,ocular surface disease, active anterior segment inflammation,peripheral corneal thinning,previous graft failures, poor compliance and increased IOP.

Penetrating Keratoplasty

Indications- any stromal or endothelial corneal pathology

Intraoperative complications- •damage to the lens or iris from the

trephine,scissors or other instruments •irregular trephination •poor graft centration on the host bed •excessive bleeding-iris and the

wound edge

DONOR CORNEA

COMPLICATIONS OF PK

Intra operative complications- •choroidal hemorrhage and effusion •iris incarceration in the wound •damage to the donor endothelium

during transplantation and handling

Postoperative Care

More complex than cataract surgery Long term success of a PK depends on

the quality of the postop care as much as on the performance of the operative technique

Topical antibiotics,tapering topical corticosteroids.

Postoperative Complications

Wound leak Flat chamber Glaucoma Endophthalmitis Persistent epithelial defect Recurrent primary disease Primary graft failure Graft rejection Corneal astigmatism

Diagnosis and Mangement of Graft rejection

Early recognition is the key to survival of an affected corneal graft

Occurs in four clinical formsEpithelial rejectionSubepithelial rejectionStromal rejectionEndothelial rejection Treatment-topical corticosteroids-

dexamethasone 0.1% or prednisolone 1%

Advantages of PK

Full-thickness tissue eliminates interface-related visual problems

Disadvantages of PK

Difficult to determine anterior corneal curvature,leading to significant refractive error

Post operative astigmatism Ocular surface disease or neurotrophic

cornea leads to prolonged healing or persistent epithelial defect

Lamellar Keratoplasty

2 types Superficial Anterior Lamellar

Keratoplasty(SALK) Deep Anterior Lamellar

Keratoplasty(DALK)

Superficial Anterior Lamellar Keartoplasty

INDICATIONS- Superficial stromal dystrophies and degenerations

Salzmann nodular degeneration Scars,trauma,dermoids infections Poor microkeratome dissection Corneal perforation

Superficial Anterior Lamellar Keratoplasty

Postoperative complications- loss of donor lenticule

Advantages- selective removal of pathologic tissue

more rapid visual rehabilitation Reduced risk of graft rejection Disadvantages-irregular

surface,interface vascularization

Deep Anterior Lamellar Keratoplasty

INDICATIONS- Keratoconus Infections Corneal stromal dystrophies not

involving endothelium Corneal ectasia secondary to LASIK

Deep Anterior Lamellar Keratoplasty

Intraoperative complications- Corneal perforation requiring transition

to PK Descemet’s membrane splitting Postoperative complications-

opacification and vascularization of interface, allograft rejection, inflammatory necrosis of the graft

Deep Anterior Lamellar Keratoplasty

ADVANTAGES- Tectonically stronger wound than in PK

Early removal of sutures Less dependence on topical

corticosteroids Minimal requirements for donor tissue DISADVANTAGES- Irregular interface

Descemet Stripping Automated Endothelial Keratoplasty(DSAEK)

In this procedure, descemet’s membrane and endothelium are stripped in the host eye (descemetorhexis),producing a smooth posterior stromal bed in the host.

INDICATIONS- Endothelial dystrophy Pseudophakic bullous keratopathy ICE syndrome Failed corneal grafts

Intra operative Complications of DSAEK

Poor microkeratome dissection of donor tissue

Inability to strip descemet’s tissue Loss of orientation of tissue Poor centration of trephination,leading to

a thick edge and possible epithelial growth

Intaocular hemorrhage Excessive manipulation of tissue , leading

to cell loss

Post operative Complications of DSAEK

Pupillary block Dislocation of lenticule Primary graft failure Epithelial ingrowth

Advantages of DSAEK

Rapid visual rehabilitation Independent of ocular surface wound

healing Stable corneal curvature for triple

procedures Tectonically strong Eliminates suture related problems

Disadvantages of DSAEK

Significant stromal haze,subepithelial fibrosis, or epithelial irregularity may require second procedure

Possible higher rate of endothelial cell loss