EYE BANKING & KERATOPLASTY
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