Sleeping without a pillow may help reduce elevated pressure inside the eye, according to early findings published in the British Journal of Ophthalmology. High intraocular pressure can damage the optic nerve and lead to glaucoma, the leading cause of irreversible blindness worldwide.

Researchers suggest that stacking pillows changes the angle of the neck, which may compress the jugular vein and interfere with the normal drainage of aqueous humor. This fluid supports eye structures such as the cornea and lens and helps regulate eye pressure and shape.

Intraocular pressure, or IOP, naturally shifts with body position. Moving from sitting upright to lying flat is known to increase IOP at night, making sleep posture an important factor to consider.

Study Design and Participants

To investigate this effect, researchers studied 144 adults with glaucoma. Participants included 84 people aged 44 or younger, 41 between ages 45 and 59, and 19 aged 60 or older.

Among them, 70 had normal tension glaucoma, 9 had elevated eye pressure, and 65 had primary open-angle glaucoma, the most common form of the disease, which is often linked to impaired fluid drainage in the eye.

From October 2023 to April 2024, participants provided detailed medical histories, including treatments, smoking habits, and alcohol use. Each person also received a full eye exam.

Researchers measured IOP in the right eye every 2 hours over a 24 hour period, both while sitting and lying down. When lying flat, participants’ heads were then raised to an angle of 20° to 35° (about 8 to 14 inches of elevation, depending on body size) using two standard pillows. IOP was measured again after 10 minutes.

Participants then returned to a flat position until the next reading. Each person completed four full sets of measurements with and without pillows.

Key Findings on Eye Pressure

A total of 96 participants, or 67 percent, showed a clear rise in IOP when their head was elevated compared to lying flat. On average, pressure increased by about 1.61 mm Hg.

Overall, IOP was higher in the elevated position than in the flat position (17.42 mm Hg vs 16.62 mm Hg), and it fluctuated more over the 24 hour period.

At the same time, ocular perfusion pressure (OPP), which reflects blood flow to the eye, decreased when two pillows were used (54.57 mm Hg vs 58.71 mm Hg when lying flat). Lower OPP suggests reduced delivery of oxygen and nutrients to eye tissues.

Differences Across Groups

Younger adults were more likely than older participants to experience larger increases in IOP. Higher pressure was also more common in those with primary open-angle glaucoma.

To explore the underlying cause, researchers also studied 20 healthy volunteers. They found that using pillows narrowed the inner space of the jugular veins (lumen) and increased blood flow speed, supporting the idea that neck position affects circulation.

Interpretation and Limitations

“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.”

Because this was an observational study, it cannot prove cause and effect. The researchers also note that the number of participants in each glaucoma subgroup was relatively small.

Still, they suggest the findings “may be linked to jugular venous compression induced by neck flexion, which could potentially compromise venous return and aqueous humor 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 optimizing long-term IOP management in clinical practice.”