'Bionic eye' implant restores sight
BBC News today reported that “two blind British men have had electronic retinas fitted”. Chris James, 54, and Robin Millar, 60, took part in a clinical trial coordinated by Oxford University and funded by the National Institute of Health Research.
Both men have retinitis pigmentosa, a rare hereditary condition that causes gradual deterioration of the light-detecting cells in the retina, which can lead to blindness. The electronic retinas are implants containing light detectors designed to replace the lost light-detecting cells.
Immediately following the procedures, when the implants were switched on, both men were able to detect light and are now beginning to use their restored vision. This early success in these two patients raises hope for the treatment of retinitis pigmentosa, which is currently incurable. Up to 10 further patients with retinitis pigmentosa will now be treated as part of this clinical trial, which was carried out at Oxford Eye Hospital and King’s College Hospital in London.
What was done?
The retinal implants were developed by Retina Implant AG in Germany to treat people with retinitis pigmentosa. Each implant contains a microchip containing 1,500 tiny electronic light detectors. During the trial, the implant was placed beneath the retina at the back of the patient’s eye. The patient’s optic nerve (the nerve that transmits visual information from the retina to the brain) was then able to pick up electronic signals coming from the microchip.
This delicate operation is conducted in two parts:
- First, the power supply has to be implanted. This is buried under the skin behind the ear.
- Then, the electronic retina has to be inserted into the back of the eye and stitched into position before being connected to the power supply.
Professor Robert MacLaren, who is leading the research, said: “What makes this unique is that all functions of the retina are integrated into the chip. It has 1,500 light-sensing diodes and small electrodes that stimulate the overlying nerves to create a pixellated image. Apart from a hearing aid-like device behind the ear, you would not know a patient had one implanted.”
What is retinitis pigmentosa?
Retinitis pigmentosa is a rare hereditary condition affecting around one in every 3,000-4,000 people in Europe. It causes gradual and progressive loss of the light-detecting cells in the retina. People with the condition often start noticing problems with their peripheral vision and problems seeing in low-light conditions during adolescence. By middle age, many people with retinitis pigmentosa will have greater problems with their vision and some will become blind. There is currently no cure for the condition, so any developments in treatments are a step forward.
How effective was the implant?
Before his operation on 22 March 2012, Chris James had been completely blind in his left eye for more than 10 years and could only distinguish lights in his right eye. When his electronic retina was switched on for the first time, three weeks after the operation, James was able to distinguish light against a black background in both eyes. He is now reported to be able to recognise a plate on a table and other basic shapes, and his vision continues to improve. He said: “It's obviously early days but it's encouraging that I am already able to detect light where previously this would have not been possible for me. I'm still getting used to the feedback the chip provides and it will take some time to make sense of this. Most of all, I'm really excited to be part of this research.”
Robin Millar also said he could detect light immediately after the electronic retina was switched on, and that useful vision was beginning to be restored.
How will the results be used?
Ten further patients with retinitis pigmentosa will now receive the implant at the Oxford University Hospitals NHS Trust and King's College Hospital in London. Longer-term follow-up of these patients, and the two men who have already been treated, is awaited. Both men are having monthly follow-ups.
Professor MacLaren said: “We are all delighted with these initial results. The vision is different from normal and it requires a different type of brain processing. We hope, however, that the electronic chips will provide independence for many people who are blind from retinitis pigmentosa.”
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