Auckland University researchers believe they are just five to 10 years from growing entire human corneas in the laboratory to implant into patients' damaged eyes.
Professor Charles McGhee, the head of the university's National Eye Centre, performed New Zealand's first laboratory-cultured stem cell operations on patients with damaged corneas in 2010, improving the sight of most of the affected eyes.
The stem cells are typically taken from a patient's own healthy eye in a tiny biopsy - or less commonly from inside the lower lip - and are cultured in the laboratory. The resulting tissue is implanted into the damaged eye, in some cases with the addition of the transplantation of a donor cornea.
Now Professor McGhee has told a conference of eye specialists in Melbourne that growing new corneas from stem cells is nearly within the grasp of his team, which is at the forefront of this kind of work internationally.
The cornea is the transparent dome at the front of the eye. It is about 12mm in diameter, less than 1mm thick and contains three layers of cells. It can be damaged by trauma such as chemical splashes or boiling water, or by disease. This can also cause a shortage, in the cornea, of stem cells, the cells that can develop into various kinds of tissue.
Around 250 corneal transplants are done each year using corneas from deceased donors, but the supply of donated tissue is too low to meet the demand.
In 2010, the Auckland University researchers could grow cells only for the outer layer of the cornea.
"Other people are doing it as well, but in the University of Auckland we've now grown the outer layer, the middle layer and the inner layer ... so it won't be long until we can grow them into a functional biological cornea," Professor McGhee said.
"Whether that's the whole cornea, or whether it's specific layers of the cornea - we'll suit it to the needs of the person.
"It's not unreasonable that in 10 years we might have a biological cornea created in the laboratory and transplanted into the patient. I think five to 10 years is probably the time line."
To grow a replacement cornea requires a "matrix" - a superstructure or scaffold - on which the cells can grow. Various groups internationally have experimented with human proteins and synthetic polymers.
"You can use the cornea from someone else, a donor, and remove all the donor cells, then grow all the layers of new cells on to that, so what you are essentially using is the collagen of the donor cornea."
Professor McGhee and colleagues wrote in the journal Clinical and Experimental Ophthalmology in July that six eyes in five patients had been treated in Auckland with their own stem cells that had been cultured in the lab.
Five of the eyes had done well following treatment, which included a donor corneal transplant for some, but in one eye the treatment had failed after initial success.
How it's done
*A tiny piece of tissue is taken from a person's healthy eye.
*The tissue contains stem cells, which can be developed into various cells in the laboratory.
*They are grown into the kind of cells required for the cornea, on a membrane derived from human placenta.
*The resulting tissue is implanted into the patient's injured eye.
*To grow an entire cornea in the laboratory.