Non-invasive treatment partly restored sight to people with optic nerve damage
Electrical current stimulation helped the brain reorganise to see better in people with some remaining vision.
Results from a clinical trial in Germany show that a non-invasive treatment has given some sight back to people with glaucoma and other conditions that cause optic nerve damage. Participants in the study also found that their sight-related quality of life got better in terms of reading and mobility. The results are published in the journal PLOS ONE.
Sight loss due to glaucoma or other causes of optic nerve damage is irreversible. At least, that has been the case with the knowledge we’ve had up to now. The optic nerve is a specialised cable that sends visual information from the eye to the brain, in the form of electrical signals.
It’s actually a bundle of wires (axons) that come from individual nerve cells in the retina. When these wires are damaged, for example due to raised pressure in the eye in glaucoma, or compressed by a tumour, or due to an inherited disorder, the connections are destroyed.
Current treatments don’t restore sight
Current treatments, such as eye drops to reduce pressure in the eye, can only prevent further damage. Sight that has already been lost can’t be recovered.
But in the current study, the researchers used electrical stimulation with the idea of getting the remaining optic nerve connections to reorganise themselves and cover for the missing wires.
Patients with optic nerve damage from various causes took part in the study: 33 with sight loss due to glaucoma and another 32 with causes including Leber hereditary optic neuropathy, inflammation (anterior ischemic optic neuropathy) and optic nerve compression.
The treatment group (45 patients) had a daily 50-minute session of alternating current stimulation for 10 days (with the weekend off). Alternating current stimulation involved sending bursts of electrical signals between 5-25 times per second, through 4 small electrodes placed flat against the skin near the eyes. Another 37 patients were given a ‘sham’ treatment of just one burst per second.
Everyone’s sight was tested before, 48 hours after and, finally, 2 months after the treatment ended. They also had their brainwaves measured (EEG), were asked every day if there were any side effects and completed a questionnaire about their quality of life.
Changes to brain activity
Results showed that participants in the treatment group were 24% better at the sight test after treatment than they were at the start. The improvement lasted for at least 2 months, at which point they were tested again. In comparison, the sham group were 2.5% better after treatment. EEG recordings showed that certain nerve cells in the brain changed the way they were working together after treatment, so that they became more synchronised.
“This is a hugely important study for people who have lost some of their sight to optic nerve damage,” said Dr Dolores M Conroy, Director of Research at Fight for Sight. “Glaucoma is the second leading cause of blindness worldwide and impairs vision in around 60,000 people in the UK. Until now, that sight loss has been irreversible. What the current study shows is that, while the lost nerve cells are not coming back, it is possible to get the remaining nerve cells to work together more effectively, boosting the vision that’s left.
Better vision, reading, mobility & orientation
“It’s very exciting that this potential treatment is non-invasive and seems relatively free of side effects. The patients themselves experienced improvements in vision, reading, mobility and orientation. We still have a lot to understand about exactly what’s happening as the brain reorganises itself, for example what are the limits and how well does the treatment fare in the longer term, but these are very impressive results that will drive restorative vision research forward.”
Fight for Sight is funding Dr Tony Redmond at Cardiff University to find out more about how the brain reorganises itself in people with glaucoma. The results could lead to a better way to detect glaucoma early on.
Find out more about Fight for Sight’s glaucoma research.