China-led study finds way to reverse a loss of eyesight
- Breakthrough research suggests multiple injections in the eye could be reduced to a single, more effective shot
- Study was led by Tian Ying, an ophthalmologist at the Beijing Chaoyang Hospital, with key input from an Australian immunologist
About 450 million people worldwide are affected by loss of vision due to age or chronic disease. It was once regarded as a natural process, but in recent years scientists have found most of the blindness is caused by an excessive growth of new blood vessels at the back of the eye.
Exactly why an ageing eye rapidly grows blood veins remains unclear, but stopping the process could help restore light to many elderly or diabetic patients.
The growth of young blood vessels relies heavily on a protein known as vascular endothelial growth factor (VEGF). Some pharmaceutical companies have developed antibodies that can be injected into the eye and bind with the VEGF protein.
However, the therapy is effective for only 40-60 per cent of patients and repeated shots are often required, leading to a higher risk of eye damage and prolonged suffering.
Around the world, medical researchers are racing to develop better treatments for these eye problems that can confront almost anyone at some time in their lives.
“Our new approach aims to reduce the treatment to just one injection. Its efficiency is much higher than existing drug delivery methods,” said Tian Ying, an ophthalmologist at the Beijing Chaoyang Hospital and lead author of the study, which was published in the journal Nature Biomedical Engineering.
When analysing samples from eye patients, Tian and her colleagues from the Chinese Academy of Sciences found the antibody treatment was not enough.
The eyes of many elderly or diabetes patients contained not only more blood vessels but also molecules related to inflammation. Scientific evidence had already suggested eyesight loss is closely linked to inflammation. Other research teams have tried injecting a combination of the antibody and anti-inflammatory medication into the eye, but with little effect.
This is partly because the eye contains a lot of water, making it difficult for the antibody to find and bind with the protein that promotes blood vessel growth. The inflammation-suppressing drugs were also unable to reach the swollen tissues.
“To solve the problem, we need to think beyond the eyes,” Tian said in a telephone interview on Wednesday. In cancer studies, researchers have been using an exosome – a molecule produced by T cells – to quickly find and tame the overly active immune cells which cause inflammation. But, Tian said, the exosome had never been used to treat eyes before.
While most of the work was conducted in China, Yu Di, a leading immunologist with the University of Queensland, was pivotal in pioneering the team’s research into whether the exosome could provide a suitable treatment. Tian said the Australian researcher’s “guidance has played a key role” in bringing the idea to life.
She also said the political tensions between China and Australia – which are at their highest in decades – had not affected their collaboration.
Tian and her colleagues in China built a three-body structure that combined the inflammation-homing exosome, the antibody and a trigger protein that would separate the two drugs when they reached the targeted areas in the eye.
A human clinical trial of the new technology is still pending approval, but experiments on mice and monkeys showed it could repair more than 90 per cent of damage to eyesight. With all the biomedical composites of the new treatment already commercially available, the researchers expect human trials to start soon.
Treating diseases of the eye – one of the most sophisticated human organs – has been difficult, especially when they occur below the surface. While some symptoms can be relieved with eye drops, most medication cannot reach the back of the eye because of the many protective barriers in the way.
But the prospect of a needle in the eye is distressing for most patients, so Tian and her colleagues are working on new drug delivery systems, using cutting-edge technology such as nanoparticles – which could be delivered via drops – to make treatment easier, she said.