Cornea transplant is a procedure that replaces damaged or diseased corneal tissue (front layer of the eye) and is replaced with a healthy corneal tissue from an eye of a deceased human donor.
Indications for corneal transplantation
Keratoconus: thinning of the cornea and being shaped as an irregular cone.
Fuchs’ dystrophy: a condition in which the cornea inner layer (endothelial) dies, causing thickening and swelling of the cornea, and leading to blurred vision.
Infection/keratitis causing inflammation and permanent damage to the cornea.
Chemical or traumatic eye injury that penetrates and scars the cornea.
Types of Keratoplasty
Three surgical options are available for cornea transplant. The choice of surgery will depend on the cause of corneal damage and the condition of cornea. All cornea donors will undergo testing to make sure it is safe for transplant.
Anterior Lamellar Keratoplasty (ALK)
In most Keratoconus cases, the innermost layer of the cornea - the endothelium, is healthy. (This is the functional layer of the cornea that contains cells that pump fluid out of the cornea and maintain its clarity.) However in full thickness corneal transplantation procedures (conventional corneal grafting surgery) this layer is also sacrificed and replaced with donor tissue. The body senses this layer as being foreign and attempts to reject this tissue. Hence post-operative steroid medications are necessary for a long time post-operatively to prevent rejection of the corneal graft. Long term use of steroids can predispose to complications such as cataract and glaucoma, besides the increased risk of secondary infection.
Deep anterior lamellar keratoplasty (DALK), is a newer method of corneal surgical procedure. It is a partial thickness graft that selectively removes the diseased anterior layers of the cornea and preserves the two healthy innermost layers, the endothelium and Descemet’s membrane. As the inner layers are retained the body does not recognize the donor tissue, hence there is less risk of rejection, and steroid medications need not be continued for a long duration.
When the above mentioned treatment is not suitable for you, and a contact lens cannot be fitted satisfactorily despite all measures, the conical cornea must be replaced surgically. Keratoplasty (Corneal transplantation or grafting) is an operation in which abnormal host tissue is replaced by donor corneal tissue. Penetrating Keratoplasty is the procedure of choice, and virtually all authorities cite success rates greater than 90%. The donor tissue is fixated onto the host by means of multiple interrupted sutures.
This procedure is helpful in cases where the innermost layer of the cornea (endothelium) is damaged. The thin layer of endothelial tissue is called descemet membrane.
There are two types of endothelial keratoplasty surgeries:
Both procedures involve removing the damaged endothelial tissue and replacing it with healthy donor tissue. Few or no stitches are required during endothelial keratoplasty surgeries compared to other keratoplasty procedures. Instead, an air bubble is used to keep the donor cornea in place. The difference between DSAEK and DMEK is the thickness of cornea, DSAEK is thicker and DMEK is thinner.
Decision for the type of transplant will depend on what suits your specific eye condition. Not all patients with diseased corneas are candidates for endothelial keratoplasty. These procedures correct corneal endothelial failure, but are not able to correct corneal scarring, thinning, or surface irregularity.
What happens before a cornea transplant surgery?
Anaesthesia team will review your medical history along with your surgeon to decide on the surgical plan which is either sedation or general anaesthesia. The surgery is an outpatient procedure and the duration of surgery is usually less than 2 hours long.
What to expect after a cornea transplant surgery?
Eye redness, irritation and sensitivity to light for the first few days after surgery.
Eye pain can be controlled by over-the-counter pain medication.
Your eye will be covered with an eye patch that should be worn when showering and sleeping.
Activities that may cause a direct hit to the eye will need to be avoided.
For the Endothelial procedure, you need to position yourself face up for a few days after surgery.
Follow up will be within 24 to 48 hours after surgery. Eye patch will be removed to check on your eye’s healing.
Drops and ointment will be prescribed to help eye healing.
Stitches may not be removed for several months depending on type of stitches and surgical technique used.
Eyeglasses or protective eyewear is recommended to help protect your eye.
While recovering, rubbing and pressing on the eye should be stopped and avoided as it may damage healing.