Sleeping without a pillow may be better for people with glaucoma, a study suggests.
Stacking two pillows in bed was linked to higher pressure inside the eye among such patients.
This may be down to pressure on the jugular veins – the main blood vessels in the neck – the researchers in China said.
The study, published in the British Journal Of Ophthalmology, included 144 people with glaucoma.
The condition is usually caused when fluid builds up in the front part of the eye, damaging the optic nerve, which connects the eye and the brain.
It is most common in people over 50 years, and while it does not usually have symptoms, it can cause blindness if left untreated.
Researchers measured internal pressure in the right eye of each patient every two hours for 24 hours while sitting and lying down.
Their heads were then raised to between 20 and 35 degrees by two pillows, with pressure measured 10 minutes later before they were asked to lie down flat again.
Researchers found that eye pressure increased in more than two-thirds (67%) of the participants when they were lying on pillows, when compared to lying flat.
The position was also linked to an increased fluctuation in eye pressure over 24 hours, and a fall in the pressure at which blood enters the eye.
Lying on pillows with the neck at an angle may compress the jugular vein, which takes blood from the head back to the heart, the study suggests.
To explore this further, the team performed ultrasounds on 20 healthy volunteers and found the high-pillow position led to “significant constriction” of the jugular vein’s lumen – the hollow passageway through which blood flows.
The researchers said that people with glaucoma “may benefit from avoiding sleeping postures” that cause this compression, although further research is needed.
They added that this adjustment represented “a simple, yet potentially, effective” strategy for maintaining long-term internal eye pressure. – PA Media/dpa
