Risks of Corneal Graft Surgery

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Penetrating corneal grafts

Complications during surgery

Choroidal (expulsive) haemorrhage – usually results in loss of useful vision or loss of the eye. Estimates vary from 1:200 to 1:100 (compared to 1:600 for cataract surgery). Risk factors are thought to be: hypertension, glaucoma, previous ocular surgery, old age and coughing or straining during surgery under local anaesthetic.

Intraocular bleeding during surgery – this usually settles spontaneously, but may result in prolonged visual recovery until blood reabsorbs. Occasionally may require emergency surgery to control raised eye pressure.

Cataract – is uncommon early usually resulting from minor injury to the lens during surgery. Late cataract is more common probably due to the effect of steroid drops needed to prevent rejection in the early post-operative period.

Iris trauma – is common but is rarely identifiable after surgery. However an irregular pupil may occur and it is sometimes safer for the surgeon to remove part of the iris (peripheral or broad iridectomy) at the time of surgery; this is more often needed in inflamed eyes.

Early post-operative complications

Endophthalmitis – the risks of severe infection after surgery is probably commoner after graft surgery than other forms of surgery at about 1:500 cases. It can usually be treated effectively with prompt early therapy. Later infection can be related to loosening sutures or suture removal.

Primary donor transplant failure – when the donor cornea does not function after transplantation. About 1:400 cases.

Glaucoma (raised eye pressure leading to some loss of vision) – is very common in patients with pre-existing glaucoma (about 30-50%) and will require additional glaucoma therapy, or surgery (laser, drainage or tube surgery) to control it. In patients with no problems except for the corneal disease it is rarely a long term problem although short term raised eye pressure in the immediate post-operative period (related to inflammation) or later (due to the need for steroid drops to prevent rejection) is common. These cases are usually easily controlled but may require additional medical therapy or surgery.

Wound leaks leading to loss of fluid from the inside of the eye – are uncommon and usually settle without the need for re-stitching which is rarely needed. A post-operative appointment either the morning after surgery or within the first week is required to exclude and manage this problem.

Excessive inflammation after surgery – inflammation is normal and usually controlled by the use of steroid drops alone. Severe inflammation may occur in patients who have severe allergy, have had previous graft surgery, or previous scleritis (i.e. after Acanthamoeba infection or in Rheumatoid arthritis). This type of severe inflammation is uncommon, unpredictable but controllable with immunosuppressive therapy by mouth. Although this type of treatment commonly has short term side effects the treatment is usually only necessary for 3 – 4 months and is usually successful.

Persistent corneal ulcer – All of the skin on the surface of the donor cornea (the epithelium) is normally replaced within a few days to a year after the operation. This process is complex and occasionally fails. Use of non-preserved eye drops, ointments, therapeutic contact lenses and other measures may be needed to achieve healing.

Late complications

Corneal graft infections – occur in 1:20 to 1:50 of patients often related to the stitches or herpes (in previously infected patients). Infection may be acute or chronic (infections crystalline keratopathy) and is always serious. Corneal graft rejection may follow as a consequence of infection. Loose stitches are one of the commonest causes of this which is why regular visits are needed after surgery and why all stitches should be removed when the graft has healed, usually between 15 months to 2 years.

Corneal graft rejection – occurs in up to 20% of low risk grafts and up to 80% of high risk grafts (replacement grafts after previous rejection, corneas with blood vessels or those that are inflamed at the time of surgery). Rejection requires prompt therapy and patients need to contact me or if I cannot be contacted then attend the A&E Department at the Royal Berkshire Hospital, the Oxford eye Hospital or their local eye unit within 24 hours. Most rejection episodes can be treated with steroid drops alone. In a few cases oral steroids may be needed.

Corneal graft slippage – Corneal sutures are usually removed from a year onwards, with complete suture removal from 15-18 months after surgery in most cases. In up to 5% the graft may be found not to be fully secure, requiring further sutures to be placed at the same sitting. If graft slippage occurs later, then a return to the operating theatre for resuturing is required.

High astigmatism – astigmatism occurs where the donor cornea resting on the patients eye has a different curvature in one direction (axis) than another, and is normal after graft surgery. In uncomplicated corneal disease (keratoconus and Fuch’s dystrophy) average astigmatism is around 5 dioptres. Only about 10% of cases require further surgery (astigmatism surgery) to permit useful spectacle vision and this is usually carried out between 15 – 24 months after the initial operation. Irregular astigmatism is uncommon following suture removal but occasionally occurs and can only be corrected with a contact lens.

In complicated cases astigmatism is a much more common problem.

Cystoid macular oedema – is uncommon in patients having uncomplicated grafts without lens extraction. In uncomplicated grafts combined with cataract surgery the risk is probably the same as for cataract surgery alone (about 3%) and usually resolves spontaneously but drops or tablets may be sometimes be helpful. In patients who are having grafts following complicated cataract surgery or trauma these problems occur much more commonly (up to 50%) and may be intractable. Additional therapy with steroid injections around or into the eye may be necessary. Macular oedema is a common cause of disappointing outcomes after graft surgery in these complex situations.

Epithelial downgrowth – when the skin from the surface of the eye grows inside the eye is very difficult to treat and always requires further surgery and may eventually lead to loss of vision. It is fortunately rarer than the other conditions.

Lamellar corneal grafts

Complications during surgery:

Conversion to penetrating (full-thickness) graft – the deep dissection of the cornea required to perform a deep lamellar graft may result in tearing of the deepest corneal layers so that a penetrating keratoplasty may need to be performed. It occurs in 5-10% of planned deep lamellar grafts, and is more likely in advanced keratoconus where the tissues are already very thin and weak.

Early post-operative complications

Excessive inflammation after surgery – inflammation is normal and usually controlled by the use of steroid drops alone. Severe inflammation may occur in patients who have severe allergy, have had previous graft surgery, or previous scleritis (i.e. after Acanthamoeba infection or in Rheumatoid arthritis). This type of severe inflammation is uncommon, unpredictable but controllable with immunosuppressive therapy by mouth. Although this type of treatment commonly has short term side effects the treatment is usually only necessary for 3 – 4 months and is usually successful.

Persistent corneal ulcer – All of the skin on the surface of the donor cornea (the epithelium) is normally replaced within a few days to a year after the operation. This process is complex and occasionally fails. Use of non-preserved eye drops, ointments, therapeutic contact lenses and other measures may be needed to achieve healing.

Late complications

Interface opacity – the join between the patient’s remaining tissue and the donor cornea heals by scarring, which creates an opacity across the vision. In most cases this is very mild, but in some case can significantly reduce vision or cause glare. The acuity from a lamellar graft for keratoconus is on average 1 line less good than a full-thickness graft on a standard Snellen sight test chart. The opacity tends to slowly reduce with time, so that the vision also improves slowly over time (1-2 years).

Corneal graft infections – occur in 1:20 to 1:50 of patients often related to the stitches or herpes (in previously infected patients). Infection may be acute or chronic (infections crystalline keratopathy) and is always serious. Corneal graft rejection may follow as a consequence of infection. Loose stitches are one of the commonest causes of this which is why regular visits are needed after surgery and why all stitches should be removed when the graft has healed, usually between 9 to 18 months. Loose stitches can develop early in lamellar grafts, with symptoms of soreness or foreign body sensation. If you develop these symptoms having previously had a comfortable eye, then you need to contact me as detailed below, for corneal graft rejection.

Corneal graft rejection – occurs in up to 10% of lamellar grafts, although the consequences are rarely as serious as in a penetrating graft. Rejection requires prompt therapy and patients need to contact me or if I cannot be contacted then attend the A&E Department at the Royal Berkshire Hospital, the Oxford eye Hospital or their local eye unit within 24 hours. Most rejection episodes can be treated with steroid drops alone. In a few cases oral steroids may be needed.

High astigmatism – astigmatism occurs where the donor cornea resting on the patients eye has a different curvature in one direction (axis) than another, and is normal after graft surgery. In uncomplicated corneal disease (keratoconus and Fuch’s dystrophy) average astigmatism is around 5 dioptres. Only about 10% of cases require further surgery (astigmatism surgery) to permit useful spectacle vision and this is usually carried out between 15 – 24 months after the initial operation. Irregular astigmatism is uncommon following suture removal but occasionally occurs and can only be corrected with a contact lens.

In complicated cases astigmatism is a much more common problem.

Epithelial downgrowth – After lamellar graft surgery the skin on the surface of the eye may enter the space between the graft and the remaining recipients corneal tissue leading to the need for a regraft; because it cannot enter the eye the risk of loss of all useful vision is low.

DSEK/Endothelial Graft

DSEK grafts are vulnerable to the same complications as other corneal grafts, although the risks of expulsive haemorrhage are lower and the post-operative refraction is much less likely to be irregular or have high astigmatism. The most important complications specific to DSEK surgery are early dislocation and late interface opacity.

Dislocation of Graft

The endothelial graft may come away from the patients cornea in the first few days after surgery, resulting in corneal failure, with oedema (waterlogging) causing markedly reduced vision and often painful blisters on the corneal surface. Partial separation will often resolve spontaneously, but major or complete separation requires a return to the operating theatre for ‘rebubbling’. In this operation an air bubble is injected into the eye to push the donor material up against the patients cornea. The graft may need to be repositioned, and the air bubble kept in place for up to 30 minutes.

In some cases the donor will not adhere, or adheres but does not function. In either situation a replacement graft (DSEK or penetrating) will be required.

If the donor material has been perforated during preparation then the donor may separate into layers. This will usually resolve spontaneously, but if it does not, then rebubbling or replacement may be needed.

Poor Vision

Vision after DSEK will be poor until the donor adheres to the patients cornea and pumps fluid out of it. From 2 weeks post-op the vision should improve, with vision usually good after 4-6 weeks. If the donor graft is thick, or the interface between patient and donor heals with scarring, then vision may not be good enough for the patient. The vision usually improves slowly over the next few months, but a regraft with a new DSEK, or a penetrating graft is rarely necessary.

Thank you to John Dart, Moorfields Eye Hospital.
Modfied from: Litoff D, Krachmer J. Complications of corneal surgery. Int. Ophthalmol.Clin. 1992; 32(4): 79-95.