Sleeping with stacked pillows may unintentionally raise nocturnal intraocular pressure (IOP) in people with glaucoma, according to new preliminary research published in the British Journal of Ophthalmology.
The observational study suggests that elevating the head and neck during sleep could interfere with venous outflow, potentially worsening nocturnal IOP fluctuations and reducing ocular blood supply – factors known to influence glaucoma progression.
Researchers at the Eye Center, Zhejiang University, China, examined 144 adults with glaucoma, including patients with normal tension glaucoma, ocular hypertension, and primary open-angle glaucoma (POAG). Participants underwent 24-hour IOP monitoring, with measurements taken every two hours in both seated and supine positions. During part of the assessment, participants lay flat; during another, their heads were elevated by approximately 20–35 degrees using two standard pillows.
Across the cohort, two-thirds of participants experienced a measurable rise in IOP when transitioning from a flat supine position to an elevated one. Mean IOP was significantly higher with pillow elevation, alongside greater diurnal fluctuation. The average increase associated with pillow use was approximately 1.6 mmHg.
Notably, ocular perfusion pressure (OPP) – an indicator of blood flow to the optic nerve – was significantly lower when participants slept with elevated head positioning. Reduced OPP is considered a potential risk factor for glaucomatous optic neuropathy.
Subgroup analysis showed that younger adults and those with POAG were more likely to demonstrate larger posture-related IOP increases compared with older participants and other glaucoma subtypes.
To explore a possible mechanism, the researchers also assessed jugular vein dynamics in a small group of healthy volunteers. Imaging showed that pillow use narrowed the jugular vein lumen and altered blood flow characteristics, supporting the theory that neck flexion may impair venous drainage and aqueous humour outflow.
The authors note that current approaches to managing nocturnal IOP largely rely on medication escalation or adjunctive laser therapy. Given the influence of body position on IOP, they suggest that sleep posture modification could represent a simple, low-risk adjunct strategy worth further investigation.
However, the researchers caution that the study was observational and involved relatively small subgroup numbers, meaning causality cannot be established. Larger, longer-term studies are needed to determine whether modifying sleep posture leads to clinically meaningful benefits in glaucoma outcomes.
Even so, the findings raise awareness of sleep-related factors that may contribute to nocturnal IOP elevation and highlight the need for clinicians to consider postural influences as part of holistic glaucoma management.
