Synonyms: corneal transplant, corneal graft

Background

This is the procedure whereby abnormal host tissue is replaced by a healthy donor cornea. It has been performed for over 100 years and is the commonest and most successful of transplant procedures.¹ It may be:

• Full thickness: penetrating keratoplasty
• Partial thickness: lamellar or deep lamellar keratoplasty

This record will give you an overview of who the procedure is for and what it entails. Many of these patients will be under ongoing ophthalmological supervision and the decision to operate is made by a corneal surgeon. Follow-up will be by the surgical team: it will be frequent initially and then taper depending on the patient's progress. Complications are also outlined - if you suspect any of these, a same day referral is mandatory.

To understand the procedures, it is worth remembering that the cornea has three layers. Working from anteriorly to posteriorly: the outer epithelial layer, the thick, middle stroma and the single cell layer endothelium (whose cells cannot regenerate once damaged and which controls the hydration of the cornea, so giving rise to corneal oedema if damaged).

The patient

There are a number of reasons for performing a penetrating keratoplasty. These include:²

• Optical problems - improving vision is the most common indication. Conditions leading to keratoplasty tend to be:
  • The dystrophies (e.g. Fuchs' endothelial dystrophy - form the bulk of the older patient group)
  • The degenerations (e.g. Salzmann nodular degeneration)
  • Some corneal ectasias (e.g. keratoconus - form the bulk of the young patient group). Scarring due to trauma or infection is also an indication.
  Go to our records on Corneal Problems - Acute and Corneal Problems - Non Acute to find out more about these conditions.
  
  
• Tectonic issues - if there are severe structural changes of the cornea (e.g. thinning), a graft may be needed to preserve the corneal integrity. In this case, it tends to be an emergency procedure to prevent or treat corneal perforation.¹

Rarely, there may be therapeutic reasons (e.g. a chronic corneal infection that is unresponsive to antimicrobial treatment) and even more rarely, cosmetic reasons.

A lamellar keratoplasty is indicated where there is opacification of only a third of the thickness of the stroma or where there are diseases of the corneal margin such as corneal thinning, recurrent pterygium or limbal dermoids.

Deep lamellar keratoplasty is performed where there is disease of the anterior cornea (up to 95% involvement) but sparing of the endothelium. This might be for chronic inflammatory disease for example, which carries a high risk of graft rejection (see below).

The procedure

Donor tissue is harvested within 24 hours of donor death. As with all transplants, there are certain restrictions imposed in order to maximise positive outcome, e.g. in common with other transplant procedures, tissue is not accepted where there has been death of unknown cause. In keratoplasty, additional contraindications include a very young donor (the cornea is floppy and may give poor refractive results), individuals over 70 years old (there are low endothelial cell counts) and those with intrinsic eye disease or previous intraocular surgery.

The steps in a penetrating keratoplasty are:

• Determination of graft size - this is done pre-operatively.
• Excision of donor cornea - a corneal 'button' is prepared.
• Excision of diseased host tissue - there are a number of technical difficulties possible at this stage as the rest of the globe contents needs to be protected.
• Fixation of donor tissue - this is with interrupted or continuous non-absorbable sutures (to allow for adequate tissue healing time).
• Finishing off steps - the eye is filled with viscoelastic fluid.

What to expect

Protocols vary from unit to unit but patients can broadly speaking expect the following:

Peri-operatively

Keratoplasty is a procedure that is generally done as a day case. It may be carried out under local or general anaesthetic and may involve an overnight stay. It takes an hour or two to complete and a pad will be placed on the eye until first post-operative review. The patient shouldn't experience significant pain post-operatively (some swelling and slight discomfort can be expected).

Post-operative medical care

The patient will be given preservative-free topical steroid/antibiotic drops which are gradually tapered but which may be continued at low doses for a year or more. They may also be given a course of mydriatics (which enlargen the pupil). If there was pre-existing herpes simplex keratitis, there may also be an oral course of aciclovir. Oral acetazolamide might be given to those with coexistent glaucoma.¹

Follow up is frequent initially. A common protocol is review at a day, a week, a month and 2-3 monthly thereafter. Removal of sutures is progressive if there are interrupted sutures and is usually completed by about 12 months post procedure (although circumstances may shorten or extend this time). Some patients go on to require contact lens' wear.

Post-operative non-medical care

Once home, normal bathing and showering can resume but care must be taken not to get water in the eye for a month. If the eye gets sticky, gently wash with cooled, boiled water. Eyelid make-up should also be avoided for this time. Sunglasses can minimise discomfort but contact lenses should be avoided for at least 8 weeks - the patient should talk to their surgeon before resuming wear. It is very important that the patient does not rub their eye in the early weeks post-operatively. Additionally, an eyeshield will be given to the patient to wear whenever they sleep or have a nap, for several weeks, to avoid inadvertent rubbing of the eye.

Swimming should be avoided for at least a month. Contact sports should be avoided until the green light is given by the team to go ahead using goggles. Light work can be resumed in 2-3 weeks and manual labour in 3-4 months. Driving may be affected by a change of visual acuity and the patient should take the team's advice before starting up again.

It may take months or even longer to recover useful vision.

Complications^1,2

If you suspect any of the complications listed below, same day referral is mandatory. The patient may present to the primary or emergency healthcare services with early complications. Late complications are more commonly picked up as they develop when the patient is seen in the eye clinic.

Early
• Persistent epithelial defects (> 2 weeks' duration): look for symptoms and signs of a corneal abrasion.
• Irritation by protruding sutures: look for a red eye with associated foreign body sensation. Do not evert the eyelids as you would with a regular foreign body in the eye.
• Wound leak: if you are able to, look for a shallow anterior chamber and perform a Seidel's test (see record on Examination of the Eye on how to do this).
• Iris prolapse (through the operative wound): look for a pigmented mass within the operative wound (a peripheral incision, rather like a can opener) and an associated pupil deformity.
• Uveitis: red eye, photophobia, pain, poor vision ± headaches.
• Elevated intraocular pressures: see record on Acute Glaucoma.
• Keratitis or endophthalmitis: rare but latter is sight threatening, therefore an emergency.
Late
• Astigmatism (± need for contact lenses or refractive surgery).
• Recurrence of the original disease process - this is common with viral keratitis.
• Late wound separation and suture-related problems.
• Glaucoma.
• Cystoid macular oedema.

Graft rejection

Early: primary graft failure
• Usually occurs by the first operative day.
• Cloudy cornea in an otherwise 'quiet' eye (not red, painful etc.).
• Usually due to defective donor endothelium or operative trauma.
Late: graft rejection
• About 50% occur within the first 6 post operative months and the vast majority with a year.
• Different types (endothelial versus epithelial) can produce different clinical pictures.
• Look for evidence of a red eye, corneal clouding ± uveitis, associated with decreased visual acuity.
• This is usually due to immunological graft rejection.

Treatment is with intensive topical steroids ± periocular steroids ± systemic immunosuppression.

Prognostic factors¹

Poor prognosis is noted in patients with:

• Additional corneal problems such as vascularisation or peripheral thinning.
• Associated ocular disease such as herpes, active inflammation or uncontrolled glaucoma.

Keratoprotheses

These are artificial corneal implants. They are used in patients who are unsuitable for keratoplasty. This complicated surgery (which uses the patient's own tooth root and alveolar bone to support the prosthesis) is performed in two stages, 2-4 months apart and is limited to patients with:²

• Bilateral blindness with normal retina and optic nerve.
• Severe, debilitating but inactive anterior segment disease (e.g. chemical burns).
• Multiple previously failed corneal grafts.
• Patients with good motivation.

About 80% experience visual improvement; the remainder is often found to have pre-existing optic nerve or retinal dysfunction.