For Christmas, I received The Best American Essays 2010, edited by Christopher Hitchens. So far, the most interesting among them has been “The Elegant Eyeball” by John Gamel, originally published in The Alaska Quarterly Review.
Despite being slightly astigmatic, I had never given much thought to eye health or ocular diseases. What was most startling and unsettling about Gamel’s account was the description of the pain associated with maladies like dry corneas or glaucoma. For some reason, I had assumed that eye illnesses simply involved the painless loss of sight, not the sort of agony he describes.
Ultimately, the essay is a reflection on the inevitability of deterioration and death in human bodies – the way time invariably takes away the most precious, necessary, and appreciated of human faculties. Gamel describes one patient – a professor of anthropology at Stanford – who responded to Gamel’s ultimate inability to stave off his macular degeneration with a mixture of realism and humility: “Why so sad, doctor? You look like you just lost your best friend. Who do you think you are – a magician, a god who turns old men into young men?”
Gamel does describe one area where there has been significant progress: in the use of intentional retinal scarification using lasers, to reduce the rate and seriousness of sight loss associated with diabetes. He describes how the treatment has helped hundreds of thousands of people to read and drive for years after diabetic retionopathy would otherwise have blinded them.
Such successful extensions aside, the resounding message of Gamel’s piece is that our own sense of the inevitability of our extending lives and vitality is an illusion. As such, we had best make full enjoyment of our vision while it remains acute.
It certainly makes sense that eye diseases would hurt, since vision is so important. Pain is a cue that your body is taking damage in a significant way, isn’t it?
Seeing into the future
Medical technology: The first commercial retinal implant is about to go on sale. It may be crude, but so were the first cochlear implants, 26 years ago
THAT it is possible to have a phone conversation with someone who is deaf shows just how far cochlear implants have come. Today’s devices, which are routinely implanted, can stimulate the auditory nerve across a broad range of frequencies. This allows users to hear and understand speech in noisy environments, without needing to lip-read, and even to hear and appreciate music in many cases. But the earliest cochlear implants could do none of this; instead they merely provided some basic sounds to assist with lip-reading. Nevertheless, when they first received clinical approval, 26 years ago, they were hailed as a medical miracle. Now retinal implants are at a similar point, as the first such device is about to be granted clinical approval in Europe and will then go on sale.
The device, called the Argus II, is by no means a cure for blindness, says Robert Greenberg, the chief executive and co-founder of Second Sight, the company in Sylmar, California, that developed it. It is intended for use by people who have lost their sight as a result of retina-wasting diseases such as retinitis pigmentosa, and like the earliest cochlear implants it is designed to provide only some basic sensory assistance. But despite its limitations all 30 of the people who have received the Argus II as part of clinical trials can, at the very least, now see changes in light levels and detect objects. This means that they can navigate around obstacles, find doorways, see parked or moving cars and look at someone’s head when talking to them. A handful of them can even read large print.
For the researchers who have spent many years developing these devices, and for the hundreds of thousands of blind people who stand to gain from them, the approval of the Argus II will mark an important turning-point. “The blind community have been waiting for this for decades,” says Lyndon da Cruz, a consultant retinal surgeon at Moorfields Eye Hospital in London, who has already implanted seven of the devices as part of the trials. “It’s almost unbelievable that it’s coming to market,” he says. “Very few people would have expected that there could be an artificial retinal device on the market by 2011.”
A different “biomimetic” approach (in other words, inspired by nature) is to engineer a material from scratch to have characteristics found in natural materials. Tissue engineers in Britain are doing just that to treat corneal scarring, a painful eye condition that affects millions of people, particularly in the developing world. When the cornea, the transparent front part of the eye, is damaged seriously enough to wipe out its resident repair team of limbal stem cells, scarring and blindness can result.
The most successful existing treatment involves extracting limbal stem cells from a healthy eye, cultivating them on human amniotic membrane (harvested from human placentas) and then surgically grafting this to the damaged eye. But this requires a well-stocked tissue bank and a biological clean room, both of which are in short supply in many developing countries. And the implants are often rejected: the long-term success rate for this operation is less than 50% after three years.
Sheila MacNeil, a professor of tissue engineering at the University of Sheffield, wondered whether this was due to damage to tiny niches in the cornea where limbal stem cells are thought to reside. Without these refuges, colourfully known as the palisades of Vogt, the transplanted stem cells could not survive. Ms MacNeil and her colleagues created a scaffold that incorporates artificial palisades of Vogt by building up an electrospun polymer called PGLA, commonly used in dissolvable sutures, on a carefully designed template created using a form of 3D printing called micro-stereolithography.