Elevated Head Position in Sleep May Increase Eye Pressure in Glaucoma Patients, Study Suggests

A preliminary study published in the British Journal of Ophthalmology suggests a potential link between sleeping with an elevated head position, such as with pillows, and increased internal eye pressure (IOP) in individuals diagnosed with glaucoma. Conversely, sleeping without head elevation could potentially contribute to lower IOP.

Researchers propose that neck flexion caused by pillows may compress the jugular vein, thereby impeding the natural drainage of fluid from the eye.

Context of Glaucoma and Intraocular Pressure

Glaucoma is recognized as a leading cause of irreversible blindness globally, frequently associated with elevated intraocular pressure (IOP). Elevated IOP is a well-established factor contributing to optic nerve damage.

Internal eye pressure is known to fluctuate with body posture, with the transition to a supine position during sleep identified as a primary contributor to increased IOP overnight. Aqueous humor, a fluid vital for nourishing eye tissues and maintaining eye shape and pressure, plays a critical role in IOP regulation.

Study Design and Methodology

This observational study was conducted between October 2023 and April 2024, involving 144 adults diagnosed with various forms of glaucoma. Participants included individuals with normal tension glaucoma, ocular hypertension, and primary open-angle glaucoma. Each participant provided medical histories and underwent comprehensive eye examinations.

Researchers measured the internal eye pressure of the right eye every two hours over a 24-hour period, both when participants were sitting and when lying down. During the supine measurements, participants' heads were elevated between 20° and 35° using two standard-sized pillows, and IOP was measured after 10 minutes. This measurement process was repeated multiple times for each participant, allowing for a direct comparison of IOP in supine positions both with and without head elevation.

Key Findings

The study's findings indicated that 96 participants, representing approximately 67% of the total, experienced an increase in IOP when their heads were elevated. The average increase observed was approximately 1.61 mm Hg.

Overall, IOP was significantly higher in the elevated head position, averaging 17.42 mm Hg, compared to the supine position without elevation, which averaged 16.62 mm Hg. The study also noted greater IOP fluctuations over a 24-hour period when pillows were used.

Ocular perfusion pressure (OPP), which reflects blood flow to the eye, was significantly reduced from 58.71 mm Hg in the supine position to 54.57 mm Hg when two pillows were used. A reduction in OPP indicates decreased blood flow, which delivers oxygen and nutrients to ocular tissues.

Further analysis showed that younger adults and individuals with primary open-angle glaucoma were more likely to exhibit significantly greater increases in IOP. An assessment of postural jugular vein blood flow, conducted in 20 healthy volunteers, supported the proposed mechanism, indicating that the inner cavity of the veins was more restricted and blood flow was faster when pillows were used compared to without.

Proposed Mechanism and Implications

Researchers propose that the observed IOP increases may be linked to jugular venous compression induced by neck flexion when the head is elevated. This compression could compromise venous return and the natural outflow of aqueous humor, leading to elevated internal eye pressure.

The study suggests that positional modification could serve as a plausible adjunctive strategy for nocturnal IOP management, potentially complementing existing treatments such as medications or laser therapy.

Researchers indicate that glaucoma patients might benefit from avoiding sleeping postures that induce jugular venous compression to mitigate postural IOP elevation, presenting this as a simple, potentially effective supplementary approach for long-term IOP management.

Limitations

The study acknowledges several limitations. As an observational study, it cannot establish a definitive cause-and-effect relationship between pillow use and IOP changes. Additionally, the number of participants within each specific glaucoma subgroup was small, which could affect the generalizability of some findings. Further research is necessary to confirm these preliminary observations.