The disease leads to reduced vision and affects more than 14 million people worldwide.
"Our new results indicate that branch retinal vein occlusion is caused by thickening of the arterial wall," said Mette Bertelsen, researcher at the University of Copenhagen.
"This makes it crucial for doctors to treat patients diagnosed with the disease with medicine to lower blood pressure in order to prevent blood clots from forming in the heart and brain. Branch retinal vein occlusion is often a sign of increased risk of blood clots in other parts of the body," Bertelsen said in a statement.
Bertelsen and colleagues photographically verified the diagnosis of branch retinal vein occlusion in 1168 people. They identified the patients' other diseases with the help of Danish national registries and compared the data to that of healthy people.
By looking at the illness and mortality statistics of Danes diagnosed with a blood clot in the retina's main blood vessels, both before and after the occurrence of the retinal blood clot, researchers have now shown that while these patients show a higher frequency of arterial disease in the heart and brain, they do not display a higher frequency of venous disease.
This new knowledge, which has been published in the British Medical Journal, means that disease prevention and treatment of these patients should be targeted at hypertension, diabetes and atherosclerosis, while doctors can save patients from unnecessary treatment with anticoagulants.