Glaucoma, the second leading cause of blindness in the world, is a condition that occurs when too much pressure builds up inside the eye.

This excess pressure pushes back the blood trying to enter the eye resulting in vision loss.

“It seems that hypertension might damage the blood vessels in the eye so that they cannot compensate for changes in blood flow when eye pressure increases,” said author Bang Bui from the University of Melbourne in Australia.

Previously, it was thought that high blood pressure could counteract the high eye pressure that leads to glaucoma.

This theory was supported by past research that had shown raising blood pressure for a short period of time (one hour) offered some protection against elevated eye pressure, as high blood pressure ensured that blood continued to enter the eye.

The authors tested this hypothesis by comparing the effect of acute (one hour) and chronic (four week) hypertension in lab rats with elevated eye pressure.

“When we raised blood pressure… for four weeks, we did not get the same protection against eye pressure elevation as in the (one hour) case,” Bui added.

“What this means is that having high blood pressure for a longer time has compromised the eye’s capacity to cope with high eye pressure,” Bui said.

Instead of viewing hypertension as beneficial in the fight against the disorder, Bui suggested, it should be identified as a risk factor.

The study appeared in the journal Investigative Ophthalmology & Visual Science (IOVS).