A team of researchers at the University of Edinburgh, United Kingdom has demonstrated that a simple 3D scan of eyes done with a method known as optical coherence tomography (OCT) can be utilised to track kidney health. The study found that 3D images of retina taken with OCT can identify and predict the progression of chronic kidney disease accurately.
Their research showed that thickness of retina and choroid layer (spongy layer of tiny blood vessels providing nutrients and oxygen to retina) in eyes is reduced in people with chronic kidney disease compared to those who are healthy.
This method offers a quick and non-invasive way to monitor kidney health. It can greatly improvise the monitoring of chronic kidney disease as it does not show symptoms in early stages.
Chronic kidney disease-a global burden
Chronic kidney disease is a health condition affecting millions of people globally. There is progressive loss of kidney function over a period which ultimately result in kidney failure. It is often associated with various cardiovascular issues such as hypertension and heart ailments. The survival of people with kidney failure is prolonged by kidney transplantation. However, they might still be at a high risk of developing cardiovascular conditions.
Early detection is vital for the management of chronic kidney disease. However, current methods cannot detect this condition until half of the kidney function is disrupted. The affected individuals have an unmet requirement for a novel biomarker that can reliably track damage to kidney, respond to treatment and predict long-term outcomes.
Small blood vessels changes
In this condition, the density of small blood vessels reduces. Currently, these changes can be assessed with a kidney biopsy that is invasive.
The microvascular changes can also be observed in the eye. The transparency of fluids in the eye provides an opportunity to directly observe the microvascular changes. It can be done via OCT scanners that use light waves to generate a cross-sectional image of retina in the eye along with choroid layer, within minutes.
The thinning of retina and choroid layer
In the study published in Nature Communications, OCT imaging was done in 204 people at different stages of chronic kidney disease. It includes 112 persons with chronic kidney disease and 92 who have undergone a kidney transplant upon kidney failure. Imaging was also done in 86 healthy individuals along with kidney donors.
Upon evaluation of the images, it was found that the thickness of retina and choroid is reduced in those with chronic kidney disease as compared to healthy individuals. The thinning progressed along with the decline in kidney function. Greater the severity of the condition, more is the thinning of retina and choroid layer. These changes were independent of age and sex. Kidney donors also displayed gradual thinning of choroid over a period of 12 months.
When the kidney function is restored with a successful kidney transplant, the thickness of the retina and choroid becomes normal like those in healthy individuals.
“We predict that a major reason for these changes is an alteration in the microcirculation of the eye. Some changes might be due to a reduced blood flow in the small blood vessels,” says Dr Matthew A Bailey, professor of renal physiology, University of Edinburgh. We have evidence that there is reduction in the number and complexity of the blood vessels that make up the eye’s microcirculation as kidney disease progresses, he adds.
Future course
“We hope that this research, which shows that eye is a useful window to the kidney, will help identify more people with early kidney disease – providing an opportunity to start treatment before it progresses,” said Dr Neeraj Dhaun, professor of nephrology, Centre for Cardiovascular Science, University of Edinburgh, in a statement.
In future, regular eye check-ups can help detect and monitor the condition early. It can allow people to change their lifestyle to prevent the progression of the condition. Moreover, this technique can also help in the development of new drugs as changes in retina can reflect the response of kidneys to these new treatments.
“We are building up data bank of OCT images of the eye taken from people with a number of different kidney diseases, including those recovering from acute kidney injury,” says Dr Bailey.
