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Corneal Surgery

Diseases of the Cornea and Anterior Segment of the eye are increasing in prevalence. As we age, the incidence of age-related corneal degeneration increases, and corneal diseases are a significant cause of blindness in both developed, and developing countries. Fortunately, developments in surgical technique and ophthalmic technologies now allow us to successfully treat many blinding corneal conditions. Current forms of Corneal Transplantation, Artificial Cornea Surgery, Artificial Iris Surgery, and Pterygium Surgery can now be performed with less complications and good success rates.

The Cornea

The cornea is the clear transparent window at the front of the eye, allowing light to focus and enter the eye. If the cornea is damaged or distorted by injuries or infection, or becomes cloudy due to various corneal diseases, vision may be significantly reduced, or lost. The cornea has several layers consisting of different tissue layers – some corneal diseases affect only inner or outer layers, while other corneal diseases may affect all the layers of the cornea.

Corneal Transplantation

Corneal Transplantation is a surgical procedure, in which the diseased layers of the cornea are replaced by healthy donor corneal tissue donated by another individual when he or she passes away. The replacement of the cloudy cornea, with a clear and healthy new cornea, restores vision to the corneal transplant patient.

Current forms of Corneal Transplantation

The Cornea consists of several layers, and in many patients, not all the layers are diseased or damaged. In the past, corneal surgeons only performed one main procedure – the Penetrating Keratoplasty (PK) operation, whereby the entire central aspect of the cornea was replaced by a donor cornea – a full-thickness transplant.

Penetrating Keratoplasty

Today, several forms of corneal transplantation procedures exist, and it is now possible to selectively replace different layers of the cornea, whilst retaining the unaffected layers. The major advantages to just replacing the diseased layers, and leaving the healthy layers untouched, include a stronger eye after surgery, good visual quality, relatively quick visual recovery, and most importantly, a marked reduction in complications, both during and after surgery, which leads to good success rate overall. These forms of partial thickness corneal transplantation are termed Lamellar Keratoplasty procedures.

There are basically 2 forms of modern Lamellar Keratoplasty:

Anterior Lamellar Keratoplasty (ALK)

ALK procedures involve exchanging only the front layers of the cornea, leaving the innermost layer (the Endothelial Layer), intact and unchanged. The commonest ALK procedure today is Deep Anterior Lamellar Keratoplasty (DALK), where all the front layers of the cornea are fully exchanged. The major advantage of DALK is that the risk of corneal transplant rejection is reduced to a 1-2% risk, compared to PK surgery, where the risk of rejection may be as high as 10-15%. With a DALK procedure, it is also often possible to achieve the good visual quality, and because the risk of rejection is much less, less anti-rejection steroid eyedrops are used after surgery, which also means a reduction in other complications such as glaucoma, and infection.

Deep Anterior Lamellar Keratoplasty

Endothelial Keratoplasty (EK)

In many instances, corneal clouding is due to an ageing or abnormal innermost layer of the cornea, known as the Endothelial Layer, which consists of Endothelial Cells which are either insufficient in numbers or are damaged. EK procedures leave the front layers of the cornea intact, and instead just exchange the innermost layers which contain the endothelial cells needed to keep the cornea clear. Because the donor endothelial layer is usually inserted through as small side incision (similar to “keyhole surgery”), there are no sutures on the cornea (“sutureless surgery), and vision recovers much at an earlier rate than PK or ALK. EK is usually performed as a Day Surgery procedure, and can also be performed under Local Anesthesia (LA)(just an anesthetic injection around the eye), as opposed to a full General Anesthesia (GA). The risk of transplant rejection is also much lower than PK, and ranges from 1-4%.

There are 2 forms of EK surgery, DSAEK (Descemets Stripping Automated Endothelial Keratoplasty), and DMEK (Descemets Membrane Endothelial Keratoplasty).

Descemets Stripping Automated Endothelial Keratoplasty

In DSAEK, a slightly thicker layer of inner corneal tissue, consisting of several layers, is transplanted – this procedure has been shown to have good vision restoration, less complications – rejection as compared to PK, in the region of 2-4%, and is therefore a relatively common form of transplantation in the West and in advanced countries.

Descemets Membrane Endothelial Keratoplasty

DMEK is a relatively later version of EK surgery in which only the innermost membrane and the endothelial cells are transplanted – this thin and delicate layer makes the surgery more challenging, and only a few surgeons perform this procedure at present, but the main advantages of DMEK is that the rejection rate is only about 1%, and DMEK offers good quality vision after surgery.

In both DSAEK and DMEK, repeat corneal transplantation can be more easily performed, as compared to PK surgery, and can also be combined with other forms of surgery such as cataract removal and intraocular lens implantation at the same sitting.

Artificial Cornea Surgery

Corneal transplantation may not be the ideal treatment for some of the more severe corneal diseases. In some patients, who have previously had failed corneal transplants, and in some severe cases of chemical or thermal injuries affecting the cornea, in certain severe dry eye or inflammatory states, an Artificial Cornea (otherwise known as a Keratoprosthesis, or KPro) may be indicated.

Pterygium Excision with Conjunctival Autograft

New Forms of Pterygium Surgery

The current innovation in pterygium surgery is Conjunctival Autografting using Fibrin Glue – this procedure uses fibrin glue to attach a conjunctival graft (taken from under the eyelid) in pterygium excision – this procedure has the lowest rate of recurrence of the pterygium (in the region of 1-2%), provides a good cosmetic result, and is sutureless surgery, which reduces patient comfort after surgery.

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