Corneal transplantation is also known as a corneal grafting or keratoplasty and involves removal of the central section of a diseased or scarred cornea with clear, healthy corneal tissue from an eye bank. This may involve removing the patient's entire cornea (full thickness) or only the stromal tissue, leaving the patient's endothelial cells intact (partial thickness). Corneal transplantation is offered to patients with advanced keratoconus or corneal scarring and who can no longer obtain functional vision with contact lenses.
It is a highly successful operation: when performed by an experienced corneal surgeon, graft survival rates are over 90% after 10 years and the average life of a transplant is around 15-20 years.
Only about 15% of people with keratoconus will ever need to consider a corneal transplant. That number is diminishing with the introduction of corneal collagen crosslinking to halt progression in keratoconus and more advanced, specialised contact lens designs for keratoconus.
Corneal transplantation is a life changing procedure and no keratoconus patient should consider having a corneal transplant until they have exhausted all contact lens options. These contact lenses need to be fitted by a specialist contact lens fitter for keratoconus - most general optometrists do not have experience in fitting contact lenses on people with keratoconus.
Poor fits can deter patients from wearing contact lenses and lead them to seeking premature surgery and notably corneal transplantations.
Should I have a corneal transplant?
The decision to have a corneal transplant is not easy and needs to be taken in conjunction with a patient's corneal surgeon, contact lens fitter and family. A number of factors need to be considered.
- there are many risks associated with the operation including infection, retinal detachment, glaucoma, cataract (especially resulting from high use of steroids to control inflammation and rejection) and complications from the anaesthetic.
- the graft can reject at any time and is susceptible to damage from sharp objections and blows. Contact sports are contraindicated.
- rejection can often be reversed if treated quickly enough - within hours or days of the first symptoms appearing (see below).
- post operative vision is unpredictable and a majority of grafts recipients are affected by astigmatism requiring further vision correction with spectacles or contact lenses to achieve best corrected vision. A corneal transplant should not be considered as an alternative to wearing glasses or contact lenses.
- recovery times are long. Stitches may remain in place for 12-18 months and vision may not stabilise for 2 years. This may impact on a patient's education, work and family life.
- Although repeat corneal transplants can be performed, success rates for second and subsequent corneal transplants are much lower than for the first graft.
- Corneal transplants are covered by Medicare for public hospital patients and by private health insurance in Australia. Patients without private health cover and who wish to choose their own corneal surgeon can expect to pay at least $5,000 per eye for the operation.
The first ever corneal transplant was performed in 1905 and the first in Australia was performed in 1940. There are about 1,500 corneal transplants performed each year in Australia and about 300 of these are for keratoconus. Donor age is not important; most donors are in their seventies.
The cornea has to be retrieved within a few hours of the death of the donor. The cornea to be transplanted is screened for diseases and assessed for its viability, i.e. how healthy is the cornea; it is then stored in a special nutrient solution at the Eye Bank until the transplant operation. As the cornea has no blood vessels the donor and host do not have to be tissue matched. The patient is adequately anaesthetised either with local anaesthesia or by a general anaesthetic.
The cornea to be replaced is carefully removed with special instruments usually 8.0-8.5mm diameter, the actual area to be replaced is determined by the extent of the disease in the cornea. The cornea to be transplanted is usually 8.5-9.0mm diameter and is stitched in place with great precision by an eye doctor specialising in corneal surgery i.e. a corneal surgeon. Often the corneal surgeon uses twelve clock-hour nylon stitches in combination with a continuous band nylon stitch for maximum strength.
The surgery usually takes approximately 60-90 minutes. This delicate process can be considered like removing the skin of one ripe tomato and stitching it on the skin of another ripe tomato and expecting to end up with a smooth and regular shape. Anti-rejection drops (steroids) are required for many months or years depending on the degree of inflammation. The corneal surgeon will carefully monitor the dosage rate.
Individual stitches may be removed as the healing continues to allow some controlled reshaping of the transplanted cornea. Even after only a few months the new cornea, complete with stitches, will usually have a more regular shape and often will give much better vision than was possible before the operation. The stitches or sutures usually remain in place from 12 to 18 months, but this can vary depending on the individual's healing rate and the corneal shape.
Due to the large amount of swelling in the transplanted cornea during the healing process, it is impossible to predict the quality of vision that may be possible when the stitches are still in place. Only a few months after all the stitches have been removed can reliable measurements be made regarding the shape of the transplanted cornea and the refractive error.
If the final corneal shape is reasonably regular and the focussing error is not greatly different from the other eye, then a spectacle correction is usually possible. If the corneal shape is irregular or has very high astigmatism or the focussing error is quite different from the other eye, then a hard contact lens is necessary. Miniscleral hard contact lenses can vault the transplanted cornea and substantially improve comfort and stability.
Deep anterior lamellar keratoplasty (DALK) is a partial thickness graft that preserves the inner most layer of the cornea, the endothelium. This layer keeps the cornea clear by removing fluid from the bulk of the cornea. The donor cornea has its own endothelium removed and the donor epithelium and stroma are held in place by sutures. A graft rejection usually begins in the endothelium, and by retaining this layer the chance of a potentially blinding graft rejection episode is greatly reduced. Retaining the endothelium also adds to the structural integrity to the post-graft cornea.
This surgery is technically more demanding as it involves dissecting the cornea. Due to the interface between the donor and host tissue, the final visual result is often slightly reduced when compared to the vision from a penetrating keratoplasty. A penetrating keratoplasty can still be performed if the DALK result is unsatisfactory.
More recently, transplants of the middle or Bowman layer of the cornea have been performed on keratoconus patients to stiffen the cornea. These may delay or reduce the need for DALK or penetrating keratoplasty.
DALK transplantation is the preferred method of corneal grafting today where possible, as it reduces the chances of rejection despite slightly poorer visual outcomes compared to full thickness grafts.
What happens to my graft after 20 - 30 years?
Most transplants function very well for very many years, in fact the transplant may last the life of the recipient, but we don't really know as yet. In 2017, a patient in Victoria had a graft that turned 100 years old. The donor was 82 years old at the time of the transplant and the transplant was performed 18 years ago. The transplant was still performing very well.
What about corneal transplant rejection? What should I look for?
GRAFT REJECTION CAN OCCUR AT ANY TIME NO MATTER HOW OLD THE GRAFT IS, NO MATTER IF THE GRAFT HAS BEEN TROUBLE FREE FOR MANY YEARS. Corneal graft rejection occurs reasonably frequently (one in twenty) and can usually be adequately controlled by early intervention with the appropriate treatment regime, usually frequent steroid drops. Initial treatments may require steroid drops every hour or even every 30 minutes around the clock, if the rejection is quite intense. If the graft rejection is detected early enough then steroid drops may only be required four times a day during waking hours. Occasionally maintenance low dose steroids may be required for months or years to keep a graft clear and to prevent inflammation.
RSVP - an important reminder
- R for redness - the white part of the eye becomes red, next to the cornea
- S for soreness - feeling gritty, sandy or sore
- V for vision- hazy or foggy vision
- P for photophobia- sensitivity to light
Anytime these symptoms occur, even if you only have one of the symptoms, you need to consult your optometrist or ophthalmologist urgently, to check if you are having a graft rejection. Early diagnosis is essential to successfully treat a graft rejection.
Please contact Keratoconus Australia for a free booklet on corneal transplantation.