Partial success of artificial corneas

“Millions of blind and partially sighted people are being given hope they will see again after artificial corneas were successfully ‘grown’ in eyes,” the Daily Express reported.

This research was in 10 patients with disease of the cornea, a major cause of blindness worldwide. The patients were the first to be fitted with corneas made from biosynthetic tissue rather than conventional human donor corneas. Two years after surgery, all the implanted corneas were still viable, with no serious reactions or complications. Six of the patients had better vision than before their surgery.

Although the results are promising, this was an early, experimental study. Far more research in much larger numbers of patients is needed before it is known if synthetic corneal implants are a viable alternative to donor corneas. The results were not all positive and the vision in these patients was still significantly poorer compared to that in patients who had corneas from human donors (although the results were similar once the 10 patients were fitted with contact lenses).

Where did the story come from?

The study was carried out by researchers from Linkoping university, Sweden, University of Ottawa, Canada, CooperVision Inc, US, FibroGen Inc, US and Synsam Opticians, Sweden. It was funded by the Swedish Research Council and County of Östergötland, the European Union Marie Curie International Fellowship and the Canadian Stem Cell Network. The material used for the synthetic implants (called recombinant human type III collagen) has been patented by FibroGen Inc, a biotechnology company. One of the authors of this study is vice president of the company’s Protein Therapeutics and Collagen Development, and developed the material used in the study.

The study was published in the peer-reviewed journal Science Translational Medicine and reported widely in the media. The BBC correctly mentioned at the end of its report that this was an early study in only 10 people. The Daily Mirror’s headline (“Miracle of a bionic eye that can cry”) was misleading, as was the Express ’s first paragraph. Most reports tended to emphasise the positive results from the study, without including its limitations.

What kind of research was this?

The researchers point out that disease of the cornea (the transparent outermost surface of the eye, which is made of collagen) is the second largest cause of vision loss and blindness worldwide (the first is cataracts). The current treatment for corneal blindness is to replace the damaged tissue with human donor cornea, but a severe donor shortage means that, worldwide, about 10 million people with corneal damage are untreated, with the result that 1.5 million new cases of blindness are diagnosed every year. Donor tissue also has problems including infection and tissue rejection.

In recent years, scientists have developed a form of biosynthetic collagen, which they used to develop artificial corneas. Researchers think these could provide an alternative source for patients needing corneal transplants. This early clinical study is the first to test synthetic corneal transplants in humans with corneal damage and vision loss.

This type of research is called a phase 1 study, when a treatment is first trialled in humans. These small trials aim to investigate how safe a treatment is and how it works. As the researchers point out, far bigger trials are needed to test the potential of synthetic corneas.

What did the research involve?

The researchers enrolled 10 patients between the ages of 18 and 75, all with corneal damage and significant vision loss. The patients had to fulfil certain criteria such as already being on the waiting list for a first donor transplant. Nine of the patients had a type of corneal damage called keratoconus (a condition where there is gradual thinning and bulging of the cornea), and one had corneal scarring following an inflammation.

The patients all had a corneal transplant using the synthetic collagen between October and November 2007. All the patients were operated on by the same surgeon, using the same surgical technique. They had regular, detailed follow-up for two years after surgery to assess how successful the operations had been. Their vision was tested with both spectacles and contact lenses, and other factors such as intraocular pressure, tear production and corneal status and nerve function were also regularly assessed.

Two years after surgery, the vision of these 10 patients was compared to that in another 60 patients with the same condition who had undergone donor transplants two years previously. The results were analysed using standard statistical methods.

What were the basic results?

After two years, the implants in all 10 patients had been retained without problems of rejection, vascularisation or infection and without the need for the long-term steroid treatment normally associated with donor implants.

In all patients:

• Cells from the patients’ own tissue had grown into the implants.
• Nerve regeneration was observed and touch sensitivity was restored, both to an equal or greater degree than that seen with human donor tissue.
• Some blink reflex and tear production was also restored.

Seven patients developed “focal areas of haze” in areas where the new implant had been sutured to tissue. The haze was associated with other problems such as thinning of the implant and fibrosis.

At two years, the vision in six patients had improved compared to before surgery (using a measure called best spectacle-corrected visual acuity (BSCVA). Of the remaining four patients, vision remained unchanged in two and had worsened in two.

Compared to the 60 patients who had received donor implants, visual acuity was significantly lower in the patients who had synthetic implants. However, after the patients given synthetic implants were fitted with contact lenses, the two groups had similar levels of vision.

How did the researchers interpret the results?

The researchers say that the problems of haze and thinning, which reduced vision, indicate that further developments in surgical technique are needed. However, they say the results show that biosynthetic corneal implants could offer a “safe and effective alternative” to human donor implants and thus help to address the current donor shortage.

Conclusion

This small early stage study found that biosynthetic corneal tissue implanted into 10 patients remained viable two years after surgery, without causing serious complications or side effects. The implants also improved vision in some patients although results were significantly poorer when compared to patients who had donor implants (until contact lenses were used). Some patients experienced problems after surgery, which reduced the potential improvements in vision.

Since follow-up lasted only two years, it is uncertain if outcomes improved, deteriorated or remained the same after this time. In addition, as only 10 people were treated, there is a long way to go before it is known if biosynthetic corneal implants are a viable alternative to donor implants. This study warrants further clinical stages of research, involving much larger numbers of people.

Globally, corneal blindness is a common cause of blindness that is often due to trauma or infection. However, in the UK, as in most other developed countries, age-related macular degeneration, glaucoma and diabetic retinopathy are the most common causes of vision loss. These findings have no relevance to the treatment of these common conditions.