Corneal Transplants: Advancing Artificially

As an alternative to human corneal transplants, artificial corneas can offer various benefits for surgeons: the long waiting lists for donor tissue can be skipped, there is much less eye drop aftercare, and – in theory, at least – artificial corneas will outlast the predicted graft survival rates of human transplants.

Alternative corneas were first approved for use in the US in 1992 and have been steadily improving since. This year, Thomas Poole, consultant ophthalmologist at Frimley Health NHS in Surrey, became the first surgeon in England to perform an endothelial keratoplasty with an artificial cornea. The operation restored the sight of a 91-year-old patient whose human cornea transplant had failed.

The Ophthalmologist caught up with Poole to discuss how he prepared for the procedure, the stigma that patients can attach to human corneas, and his predictions for the future application of artificial versus human transplants.

What pressure did you feel being the first surgeon in England to perform this procedure?

I didn’t feel any pressure at all – because I didn’t know it was the first one in the country! It was a perfect case to do – it was a very difficult eye and the patient was elderly with many previous surgeries, including a failed human graft. I said to him, “We’ve just seen good five-year results on this new artificial graft. Would you like to be a guinea pig for it?” He agreed, I did the surgery, and everything went well. It was only afterwards that the EndoArt team – the team responsible for the synthetic implant – said to me, “Do you know that was the first one in England?”

What were your expectations ahead of the graft?

I’ve been doing ophthalmic surgery for a long time and I’m always a little bit skeptical of new innovations. And that’s why I told the patient he would be a “guinea pig,” because even if the results are good in trials, until you’ve used it yourself, you’re never quite sure. So I was delighted when it started to work.

Have you had any contact with the patient since the surgery?

I saw him recently for some of the interviews I’ve been doing. For an item on BBC London, I actually got to see his retina and optic nerve, which I’ve not seen before because of the cloudy view. To be able to do this – and not simply rely on the patient telling me that they can see better – was really amazing.

Were there any issues with the procedure itself?

We’re used to putting a thin graft inside the eye and floating it up with a gas bubble, but for the EndoArt implant you have to use a longer-lasting gas bubble, position the patient on their back for longer, and use at least one stitch. The patient ended up having four stitches. He had experienced fairly traumatic surgery in the past, which had damaged his iris. One issue was that his previously damaged iris was trying to get in between the graft and the artificial cornea, so that made things a little bit tricky.

Another issue was that the patient had a unicameral eye, which is important for endothelial corneal grafting because it is very hard to get a gas bubble to stay in the right place. As soon as the patient sits up, the gas bubble just goes into the back of the eye and doesn’t support the graft – that’s why he had to have more than one stitch.

When the EndoArt team arrived, I explained that the patient was a unicameral eye, had many previous surgeries, and was a pretty challenging case. But they told me this was typical for the kind of cases they are working on. Everyone is trying this procedure on very difficult eyes, where there doesn’t seem to be much hope with a human cornea anymore.

What advantages do artificial corneas have over human corneas?

Interestingly, I’ve found that there’s a kind of perceptual advantage. When patients are given a choice between a human or an artificial cornea, many will choose the artificial. There’s just something about having another human tissue in their eye that makes patients slightly squeamish.

Another advantage of artificial corneas is that a human cornea can fail because the patient’s immune system will attack it. There will be an inflammatory reaction, the graft might fail, and the cornea will become cloudy again. An artificial cornea doesn’t do that because it’s made of an inert plastic that the body doesn’t recognize as other tissue.

In addition, with a human graft, most ophthalmologists will keep the patient on steroid eye drops for the rest of their life. It might only require a couple of drops a week to stop the graft from being rejected, but that’s still difficult in developing countries, for example, where hospital access is limited. Indeed, it is very difficult for patients in those countries to obtain those drugs reliably for the rest of their life. But with an artificial graft, you can stop all the drops after three months.

How did you prepare ahead of the transplant?

I didn’t do a wet lab because the surgery is actually very similar to what we do anyway with corneal grafts. But the EndoArt team sent me a really good slide deck – like a tutorial – with quite extensive tips and advice on the procedure.

The day before surgery, the team went through the case with me, and, about half an hour before the operation, we went over it again. So I felt fully prepared.

How do you see this procedure evolving in the UK – and beyond?

The next five years are critical – we will be putting artificial corneas in many more eyes and then assessing the results. Publications discussing this type of implant and its vision results are already coming out thick and fast. I keep thinking of other patients of mine that would benefit from this transplant.

As for outside the UK, there is a clear unmet need in developing countries. I have performed corneal grafts in Zambia in the past 10 years, where we shipped in donor corneas from the US at great expense. Back in 1997, I worked in Tanzania, where my supervisor would do the occasional corneal graft. He said it was a “nightmare.” Follow-ups, for example, were extremely difficult – patients had to travel in from their villages by bus, which could be a five-hour journey. Later, I realized that rich patients from countries like Tanzania would fly to South Africa or the UK for a corneal graft. But now, with the artificial cornea option, the door is opening. The graft is still not cheap, but I believe it is achievable in countries without a proper eye banking service in place.