Research into retinopathy
BHF funded research is helping to find a cure for some types of sight problems. Dr Denise McDonald explains to Sarah Brealey.
The problem of retinopathy
Premature babies and people with diabetes are both at risk of vision problems. Dr Denise McDonald at Queen's University Belfast is studying these related conditions.
These are significant problems: 1,280 new cases of blindness caused by diabetic retinopathy are reported each year in England alone, while a further 4,200 people are thought to be at risk of sight loss from the condition. People with Type 1 diabetes are particularly at risk - probably because Type 1 diabetes develops at a younger age, so their bodies are affected by damaging high blood sugar levels for longer. Diabetic retinopathy affects 70-80 per cent of adults with type 1 diabetes.
A patient's view with diabetic retinopathy.
More than 60 per cent of UK babies born weighing less than 1.25kg (2lbs 12oz) will have a condition called retinopathy of prematurity, although the majority of these cases are mild.
The condition is caused partly because in premature babies, the blood vessels in the eye may not have finished developing. The more premature the baby, the greater the risk of eye problems. Then, the unformed blood vessels in the eye can also react badly to the high oxygen levels of an incubator, and grow abnormally as a result.
Dr McDonald says: “Both conditions have similarities and occur in two separate stages. First, the blood vessels are damaged. Then, secondly, damage to the retina happens when new blood vessels grow to try to heal the damaged tissue – but in the eye, the new blood vessels fail to repair the damaged tissue and instead grow abnormally into the clear jelly part of the eye. That leads to scar tissue which can pull the retina off the back of the eye and cause sight loss.”
There are some treatments, such as laser treatment, available, but these are applied late in the disease and carry some risk of collateral sight loss. Another newer therapy is anti-VEGF medications, which stop the growth of blood vessels in the eye. These are already used with good results for age-related macular degeneration (AMD) but using them for patients with diabetic retinopathy and babies is more challenging, since the retinas are already more fragile in people with diabetes and in babies their sight is still developing. Therefore, neither treatment is ideal.
Dr McDonald says: "We are focused on looking at both stages separately. The first is if we can stop the condition in the first place by preventing damage to the blood vessels. If we can understand how immature blood vessels become damaged in response to changes in oxygen, then we could try to protect them when the oxygen levels are disturbed.
“The second phase is also important: a better understanding of why the blood vessels grow so abnormally could reduce the problem when it occurs.”
She and her team carried out some tests in the lab which suggest that supplementing with antioxidants during the early phase might reduce sight problems in premature babies, although more tests are needed.
"If we can protect the blood vessels of the eye in the incubator, that would be a good outcome," she says.
If we can protect the blood vessels of the eye in the incubator, that would be a good outcome
"We are trying to look at drugs and treatments that are known to be safe in children so that we have a treatment which can be used in patients more quickly."
Thanks to the BHF she is currently looking at the role of nitric oxide, which plays a number of roles in the body. One of these is that it helps the production of special cells that can lead and guide a new network of blood vessels.
The ultimate aim is to help patients, explains Dr McDonald. “We would like to make that jump from lab research to clinic. We would also like to show that damage to blood vessels in the eye is also applicable to other parts of the body in people with diabetes. We are focusing on the eye, but what we find could be relevant to other blood vessels. So we are hoping that our research will help people with other conditions too.”
Dr McDonald says: “BHF funding has been extremely important to our research, and we are really grateful. It reflects BHF understanding of how studying blood vessels in the eye can help us understand blood vessels elsewhere, including in the heart.”