Introduction To Corneal

TransplantationLecture 14

Liana Al-Labadi, O.D.

Corneal TransplantsCorneal diseases are the second most prevalent cause of blindness & affect more than 10 million people worldwide according to WHO

The most common treatment for corneal blindness is corneal transplantation with a donor cornea

Corneal Transplant

An operation involving the central part of the cornea

It involves replacing the host cornea with a donor cornea

The operation itself is reasonably straightforward, but the recovery period often takes a long time & optometrists should be able to let their patients know what to expect during and after the surgery

Corneal Transplants

As with cataract surgery, primary care optometrists can develop & refine their clinical skills in comanaging patients who undergo corneal transplant surgery

Understanding & mastering preoperative, intraoperative & postoperative components of each procedure, optometrists can develop solid interprofessional relationships with corneal

specialists to improve the patient’s overall treatment & ouctcome

Corneal Layers

Epithelial Layer- 10% of total thickness

Bowman’s membrane- Tough layer

Corneal stroma- Primarily water

Descemet’s membrane- regenerates readily

Endothelial layer- No regeneration

Corneal Transplants

Two major types of corneal transplants

Penetrating keratoplasty (PK)- full thickness

Affected tissue removed full thickness i.e. all corneal layers

Lamellar Keratoplasty- Anterior or posterior

Indicated when a patient has:

Chronic cornea disorder- vision does not meet the patient’s needs

Patient’s vision cannot be corrected with glasses or contact lenses

Patient cannot tolerate his or her correction

Surgical OptionsPenetrating Keratoplasty (PK)

Deep Anterior Lamellar Keratoplasty (DALK)

Posterior Lamellar Keratoplasty (PLK)

DLEK

DSEK

DSAEK

DMEK

Keratoprostheses

Corneal Transplants1st corneal transplant- performed more than 100 year ago

Corneal transplants at the time involved replacing the entire thickness of the area being transplanted, even when most of the tissue remained healthy

Anterior & posterior lamellar keratoplasty did not become available until the late 90s

Problems with PK surgery

Rejection

High degree of irregular astigmatism

Cataract & glaucoma

PK risks decreased by leaving a portion of the host cornea in place- at least in theory

Pk is indeed a risky procedure

Even more difficult to develop predictable alternatives that provide visual outcomes equivalent to those of PK

Corneal Transplants

% of full-thickness corneal transplant procedures continues to decline

In 2008, over one-third of all corneal grafts were endothelial keratoplasties

% of full-thickness corneal transplant procedures continues to decline

Less risk of rejection & other complications

Recent development in techniques result in visual outcomes more comparable to those of PK

For those active in corneal surgery comanagement, recent developments may leave them confused

Important to analyze the differences between techniques & outcomes of PK & LK to get a better understanding of deep lamellar surgeries

IndicationsIndications for corneal transplant may be anatomic or functional

Anatomic indications include:

Visual- opacification, regular refractive error or higher order aberrations (irregular astig)

Reconstructive- thinning or perforation

Therapeutic- edema, dystrophies, degenerations, deposits, intractable infections or painful bullous keratopathy

Cosmetic

Functional Indications

Involve current capabilities, potential capabilities & willingness to risk change

i.e. if an anatomic indication cannot be functionally corrected with medicines or lenses or if the correction cannot be tolerated, a corneal transplant may be warranted

PK Indications

PK IndicationsKeratoconus

Keratoglobus

Corneal dystrophies: Macualr, granual & fuch’s dystrophy

Glaucoma

Trauma

Infectious

Corneal scarring or corneal edema

Congenital opacity

Corneal perforation

Bullous keratopathy

Failed Graft

PK IndicationsPreoperative consideration

Very important to consider timing of corneal transplant before recommending the surgery

Patients usually experience their best vision 4-8 month postoperatively

Before this time, vision may be worse than before the procedure

Reluctant to recommend surgery on the better eye first or on the fellow eye within six months of the initial procedure

Both eyes rarely require surgery within six months of each other

OutcomeFactors that can complicate the outcome of a corneal transplant include:

Poor eyelid anatomy or function

Severe dry eye

Chemical burns- especially alkaline

Previous radiation treatment

The presence of AC or iris-supported IOL

Elevated IOP

Uveitis

Number of previous grafts

Other surgeries- ex: Radiak Keratotomy

Surgeon’s experience

Outcome

Successful outcome

Significant improvement in the patient’s clinical condition that, in turn, improves his or her overall quality of life

Significant improvement in vision may be two or more smaller lines on an acuity chart

Ability to see with spectacles instead of contact lenses

Restoration of binocularity

Decreased glare

Less pain

Improvement in function & quality of life

Outcome

Corneal TransplantsDonor corneas

Come from someone who has expressed their wish to donate their corneas to help someone see, after their death

The donor’s cornea will have been thoroughly tested & kept in an Eye Bank for a period, before being sent to the hospital where the operation is to be carried out

Eye Bank is responsible for ensuring the donor cornea is in good condition

Eye Bank performs checks to try and ensure cornea is in good condition

Donor corneas should be free from amy infectious diseases

Must be used within 7 days- placed in sterile moist chamber

The Procedure

Anesthesia

Local block- peribulbar or retrobulbar injection

Used when general health is good

General anesthesia- Used in children

Length of procedure- 1 to 2 hours

During the operation

A circular piece of the host cornea is removed & replaced with a similarly sized piece of the donor’s cornea, which is stitched into place

Other procedures, such as CE, may be done in combination with the corneal graft

The ProcedureSutures are put into the cornea to hold the new graft in place

They affect cornea’s shape & the way the eye focuses

They are not dissolving sutures & will eventually need to be removed

Two main patterns of sutures are used:

Single running suture- left in place for 1-3 years or until spontaneous breakage occurs

Interrupted sutures- used mostly for corneas with peripheral scarring

can be selectively removed from meridians or areas of vascularization after 2-6 months

Sutures