Sleeping without pillows may help reduce nighttime eye pressure in glaucoma

Sleeping without pillows may help lower high internal eye pressure, build-up of which causes optic nerve damage and glaucoma-the leading cause of irreversible blindness worldwide–in people with the condition, suggests preliminary research, published online in the British Journal of Ophthalmology.

Stacked pillows alter neck position, which may compress the jugular vein, thereby preventing the natural drainage of aqueous humor, explain the researchers. This fluid nourishes eye tissues without a blood supply like the cornea and lens and helps maintain eye shape and pressure.

Internal eye pressure, formally known as intraocular pressure, or IOP for short, fluctuates in response to changes in body posture, and the transition from an upright to a supine position during sleep represents the primary contributor to its increase at night, note the researchers.

To explore this further, they looked at the effect on IOP of sleeping with 2 regular sized pillows, providing a head elevation of 20–35°, in 144 adults with glaucoma (84 aged up to 44; 41 aged 45 to 59; and 19 aged 60 and above).

Seventy participants had normal tension glaucoma; 9 had high blood pressure in the eye, and 65 had primary open angle glaucoma, the most common and slowly progressive form of the condition-often due to clogged up aqueous humor drainage.

Between October 2023 and April 2024, each participant provided detailed information on their medical history, including glaucoma treatment, plus any smoking and alcohol consumption, and they underwent a comprehensive eye exam.

Their right eye IOP was measured every 2 hours for 24 hours, both when sitting and when lying down. When supine, their heads were subsequently raised to an elevation of between 20° and 35° by two normal sized pillows, and their IOP measured 10 minutes later.

They then reverted to sleeping on their backs until the next measurement. Four sets of complete measurements were obtained for each participant with and without pillows.

In all, 96 (67%) participants had a demonstrable increase in IOP when transitioning from a supine to an elevated position, with an average increase of around 1.61 mm Hg.

Internal eye pressure was significantly higher in the elevated position (17.42 mm Hg vs 16.62 mm Hg), with greater fluctuations over the 24 hour period.

At the same time ocular perfusion pressure (OPP), which measures the pressure available to push blood through the eye's tiny vessels, was significantly reduced when 2 pillows were used: 54.57 mm Hg vs 58.71 when supine. Reduced OPP is an indicator of a reduction in blood flow bringing oxygen and nutrients to the eye.

When the results were stratified further, they showed that young adults were much more likely to have significantly greater IOP than older adults as were those with primary open angle glaucoma.

Postural jugular vein blood flow was assessed in 20 healthy volunteers both with and without pillows. The inner cavity of the veins (lumen) was much more restricted with pillows than it was without, while blood flow was significantly faster.

"Traditional strategies of nocturnal IOP management are primarily limited to increasing the types and frequency of IOP-lowering medications or supplementary laser therapy," explain the researchers. "Given the well-documented influence of postural changes on IOP, positional modification emerges as a plausible strategy warranting further investigation."

This is an observational study, and as such, no firm conclusions can be drawn about cause and effect. The researchers also acknowledge various limitations to their findings, chief among which were the small numbers of participants in each of the glaucoma groups.

Further research is needed to validate these preliminary findings, they emphasise, but they nevertheless conclude that the findings "may be linked to jugular venous compression induced by neck flexion, which could potentially compromise venous return and aqueous humour outflow.

"Patients with glaucoma may therefore benefit from avoiding sleeping postures that induce jugular venous compression to mitigate postural IOP elevation. Such behavioral adjustments represent a simple yet potentially effective adjunctive strategy for optimising long-term IOP management in clinical practice."