A new study has found that sleeping without a pillow may be better for people with a common eye condition.
The research, published in the British Journal of Ophthalmology, found that stacking two pillows in bed was linked to higher pressure inside the eye among glaucoma patients, which may be due to pressure on the jugular vein, the main blood vessels in the neck.
The condition, which is most common in people over 50, 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.
While it does not usually have symptoms, it can cause blindness if left untreated.
Researchers in China measured internal pressure in the right eye of 144 patients with glaucoma 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 per cent) of people 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.
Researchers said people with glaucoma “may benefit from avoiding sleeping postures” that cause this compression, although further research was needed.
They added that this adjustment represented “a simple yet potentially effective” strategy for maintaining long-term internal eye pressure.
It comes after experts estimated that glaucoma cases could rise by 60 per cent to 1.6 million in the UK by 2060.
Researchers from UCL and Moorfields Eye Hospital also said that previous estimates that suggested 700,000 people in the UK were living with glaucoma “may not reflect the current population structure”.
Using the most recent census data, they estimated that 1.1 million people in the UK currently had the condition, the equivalent of three per cent of the population over the age of 40.
