Special device invented by a top Singapore eye surgeon is used worldwide in corneal transplants

AFTER cataract operations on both eyes within a period of about three years, Mr S.R.V. Iyer began to experience glare and poor vision in his left eye.

An examination by eye surgeon Professor Donald Tan, medical director of the Singapore National Eye Centre (SNEC), revealed a detached cornea in the troubled eye, recalls Mr Iyer, 72.

In September last year, he underwent a corneal transplant operation performed by Prof Tan, who used the special Tan EndoGlide device that he invented.

Says Mr Iyer, an engineer: “The operation took about two hours. I was able to go home a few hours later.

“The vision in my left eye is today near 100 per cent perfect. I still go back to SNEC for check-ups once every few months.”

Corneal surgeries at SNEC, using the Tan EndoGlide, have so far had 100 per cent success, says Prof Tan, who invented this special inserter with some doctors at the eye centre.

Named after him, the patented inserter which looks like a thumb drive was introduced early last year. It is used to guide a donor cornea into the eye of the recipient.

This device is the first to be approved by the US Food and Drugs Administration and it is currently used worldwide in such operations.

Seven other donor corneal inserters, mostly invented in the United States, are still undergoing FDA trials.

Corneal transplants have been on the rise in Singapore, says Prof Tan. “In the 1990s, we had only 50 transplants a year. Today, we have about 350 transplants.”

He says the usual corneal transplant involves removal of the entire cornea and replacement with a donor cornea. Today, a procedure known as selective lamellar keratoplasty (SLK) is used instead.

Surgeons cut away only the affected part of the cornea — the top layer or the bottom layer — leaving much of the rest intact.

The replacement donor layer is then inserted by an endoglide through a 4.5mm incision at the side of the eye.

The cornea, the transparent front part of the eye, has three main layers — the surface layer (epithelium), the middle layer (stroma) and the inside layer (endothelium).

“So we can have different types of transplants,” says Prof Tan. “Selective lamellar keratoplasty is a much safer surgery and it’s much more effective.

This microsurgery surgery takes skill as the normal cornea is just half a millimeter thick,” he adds.

There are many eye diseases where the inner layer is normal. So it is left alone, says Prof Tan.

“The whole point is that a corneal transplant can face tissue rejection but the layer which always rejects is the inside layer.

“If that is not involved in a transplant, the risk of rejection is almost zero.”

Cell injury continues to be a negative consequence in any eye transplant surgery. Dr Tan’s EndoGlide procedure minimises this risk.

In the lamellar method, the donor layer is folded like a taco and inserted into the eye. This folding can damage delicate corneal cells. When it is unfolded, more cells are injured.

The Tan EndoGlide configures the donor layer into a double coil without the folding and this reduces cell damage.

The endoglide gently inserts the replacement corneal layer through a keyhole incision on the side of the eye.
 
The layer is then gently pulled in by a pair of forceps on the opposite side of the eye through another tiny incision. Once inside, the donor layer uncoils automatically. A small puff of air is blown in to position the
donor layer in place.

On this procedure, Prof Tan says: “We are now in a trial for 100 patients. We have done 30 cases and all have been successful.”

Some 80 Tan EndoGlide transplants have been performed in the US, Germany, Britain, Japan, Taiwan and the Middle East. An International EndoGlide Users Group has also been formed.

There are two big clinical trials being planned in the US using this method of corneal transplant.

Says Prof Tan: “We want to be one of the top five eye centres in the world for corneal transplants. I can say that in Asia, we are probably No. 1 now.”