‘Young’ cornea tissue stored, and re-implanted to correct presbyopia
By Fiona Low

Imagine having a slice of your corneal tissue lasered off, saved and kept in deep freeze when you are, say in your 30s and near-sighted.

Then, when you develop “old sight” or presboypia in your 40s, that saved flap of tissue could be re-implanted so your focusing power on nearby objects improves.

This is now a distinct possibility. The Singapore National Eye Centre (SNEC) is leading the world in developing the procedure, following the theory that corneal tissue can be re-implanted later to correct presbyopia.

Presbyopia, which causes difficulty in focusing on nearby objects, usually sets in among those aged 40 and above.

The first half of the SNEC's pioneering procedure, that of removing a slice of cornea, is also proving to be a safer and more precise treatment option than the currently popular Lasik, especially for those with more severe myopia of between 500 and 1,000 degrees.

Lasik, first performed here more than 10 years ago, permanently corrects myopia and astigmatism. The process involves using either a blade or laser to cut a flap in the cornea in the front part of the eyeball.

The flap is then lifted and a second laser machine is used to vaporise the inner layer of corneal tissue to correct vision. The flap is then replaced.

The new procedure, called Femtosecond Lenticule Extraction (FLEx), requires surgeons to use just one laser machine – one that creates the flap and then cuts into the second layer below that as well.

The big difference between this procedure and Lasik comes in at this point. Unlike Lasik, which destroys the inner corneal tissue, the new procedure removes this disc-shaped inner layer intact for possible re-implanting in future.

The SNEC has already patented this idea of “reversing” the surgery, along with the method of preserving the corneal tissue in liquid nitrogen.

Its researchers, who have been conducting trials on rabbits so far, say they will try out the re-implanting process this year, possibly on primates, which resemble humans more closely.

Developments are proceeding along another front as well: Researchers are refining the FLEx method. This involves creating an incision of just 4mm to 5mm on the first layer of the cornea instead of excising an entire flap. It is through this tinier incision – half the width of the 9mm-cut for existing FLEx and Lasik procedures – that the inner corneal layer is removed.

This improved procedure has been dubbed Small Incision Lenticule Extraction (Smile). Having a smaller cut means less post-operative discomfort for the patient, such as the tearing and dry-eye problems, which commonly follow Lasik.

Like FLEx, Smile is also suitable for those with higher degrees of myopia. Introduced here six months ago under clinical trials, these procedures have so far been carried out on 34 patients at a cost of $2,300 to $2,500 per eye. Traditional Lasik costs about $1,800 per eye.

Bank officer Frances Yap, 32, underwent Smile in March to correct her myopia, which stood at 500 degrees, and is happy with the results, saying: “I no longer have to reach for my glasses, especially in the middle of the night, when I have to attend to my children.”

SNEC director Donald Tan believes FLEx and Smile could eventually rival Lasik – and perhaps even replace it.